Open Access

Daily cycling of nitric oxide synthase (NOS) in the hippocampus of pigeons (C. livia)

  • Aline V Machado-Nils1Email author,
  • Larissa OM de Faria1,
  • André S Vieira1,
  • Simone A Teixeira2,
  • Marcelo N Muscará2 and
  • Elenice AM Ferrari1
Journal of Circadian Rhythms201311:12

DOI: 10.1186/1740-3391-11-12

Received: 1 July 2013

Accepted: 8 October 2013

Published: 1 November 2013

Abstract

Background

Nitric oxide synthase (NOS) is essential for the synthesis of nitric oxide (NO), a non-conventional neurotransmitter with an important role in synaptic plasticity underlying processes of hippocampus-dependent memory and in the regulation of biological clocks and circadian rhythms. Many studies have shown that both the NOS cytosolic protein content and its enzymatic activity present a circadian variation in different regions of the rodent brain, including the hippocampus. The present study investigated the daily variation of NOS enzymatic activity and the cytosolic content of nNOS in the hippocampus of pigeons.

Results

Adult pigeons kept under a skeleton photoperiod were assigned to six different groups. Homogenates of the hippocampus obtained at six different times-of-day were used for NOS analyses. Both iNOS activity and nNOS cytosolic protein concentrations were highest during the subjective light phase and lowest in the subjective dark phase of the circadian period. ANOVA showed significant time differences for iNOS enzymatic activity (p < 0.05) and for nNOS protein content (p < 0.05) in the hippocampus. A significant daily rhythm for both iNOS and nNOS was confirmed by analysis with the Cosinor method (p < 0.05). The present findings indicate that the enzymatic activity of iNOS and content of nNOS protein in the hippocampus of pigeons exhibit a daily rhythm, with acrophase values occurring during the behavioral activity phase.

Conclusions

The data corroborate the reports on circadian variation of NOS in the mammalian hippocampus and can be considered indicative of a dynamic interaction between hippocampus-dependent processes and circadian clock mechanisms.

Keywords

Nitric oxide Neuronal nitric oxide synthase (nNOS) Hippocampus Pigeon Daily molecular cycling

Background

Nitric oxide synthase (NOS) plays an essential role in the synthesis of nitric oxide (NO) which has an important role as a mediator in many physiological processes, including mechanisms regulating biological clocks and circadian rhythms [1]. NO synthesis results from the oxidation of L-arginine by the enzyme NO synthase (NOS) which is found as one of three main types. Two are constitutive nitric oxide synthases (cNOS): endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) and are dependent of Ca2+, and the other isoform is the inducible nitric oxide synthase (iNOS), which is independent of Ca2+[2]. The majority of the information available on the role of NO in the brain deals with nNOS, of which the brain contains the highest activity found in any tissue, and which, although present in some cerebral vessels and in glial cells, is predominantly found in neurons [2, 3]. In the CNS, NO synthesis seems to be predominantly regulated by the influx of Ca2+ through glutamate receptor channels, in particular following postsynaptic stimulation of NMDA receptors [47].

Circadian variation of both NOS activity and cytosolic protein content has been reported in several regions of the brain of rodents, such as cerebellum, brainstem, hypothalamus and hippocampus, which showed acrophase in the dark phase [8]. Rhythmic expression of NOS was also observed in total brain tissue homogenate when both exposed to light/dark cycle and to constant light [9]. Evidence indicates that like in rodents, the hippocampus of birds also has cells containing NOS, which are involved in the formation and retrieval of memory [10, 11]. Additionally, the hippocampus of the pigeon has a wide distribution of glutamate receptors [12] which can mediate the activation of NOS and NO synthesis and mechanisms of synaptic plasticity.

The diurnal oscillation of NOS in the hippocampus is similar to those described for molecules that participate in processes of consolidation and persistence of hippocampus-dependent memory in rodents [1316], which are also initiated by Ca2+ intracellular signaling originating from glutamate NMDA receptors. Many studies have shown that drugs that inhibit nNOS activity can block hippocampus-dependent processes such as long-term potentiation (LTP) and long-term memory processes [1719].

Although daily fluctuation of molecules in intracellular pathways has been described for circuits of the hippocampus in rodents [1315], a 24 h profile of the NOS activity has not been studied in the avian hippocampus. So, the analysis of molecular cycling in the hippocampus of pigeons can add important points to the set of many studies that described a coordinated set of circadian biochemichal, physiological and behavioral rhythms in a wide array of vertebrates, including birds [2023]. Particularly, pigeons have been much studied in laboratory research on circadian rhythms of feeding, thermal physiology, hormonal variation and metabolism [2427] as well as on time-of-day variation of behavior and learning [2831]. Therefore, the present study was performed to elucidate the 24 h cycling of NOS in the hippocampus of pigeons. The enzymatic activity of Ca2+-dependent (cNOS) and Ca2+-independent NOS (iNOS) and the expression of the nNOS protein were analyzed.

Materials and methods

Forty-eight male pigeons (Columba livia) were used. For 15 days, these pigeons were housed in individual cages within an isolated room, under a 12:12 h light–dark cycle (light: 1000 lux; dark: 0 lux; lights on at 6:00 h) and temperature maintained at 22°C. After this period, the light cycle was gradually changed to a skeleton photoperiod, with two 15-min pulses of bright white light (1000 lux) separated from each other by 11:45 h of dim red light (5 lux).

During four days, the animals were taken from their cage and transported to the laboratory, where they were weighed before being returned to the cages. In the fifth day, the pigeons were divided into six different groups (n = 8): ZT0, ZT4, ZT8, ZT12, ZT16, ZT20. ZT0 corresponds to the time of turning on the light. The hippocampi of the pigeons were collected after decapitation conducted at six different times-of-day, one time for each group. After brain removal, the dissection of the hippocampus was performed according to the coordinates of the atlas of Karten and Hodos [32]. The tissue was immediately frozen in liquid nitrogen and subsequently stored at −80°C. All experimental procedures were conducted in accordance with the requirements of the Ethics Committee for Animal Experimentation of the Biology Institute, UNICAMP, Brazil, (Protocol 1732–1).

The enzymatic activity of cNOS [33] was analyzed in samples of hippocampus of pigeons pertaining to each group. The samples were homogenized in 5 V of cold incubation buffer (50 mM Tris–HCl buffer, pH 7.4) containing 1 mM phenylmethyl-sulphonyl fluoride (PMSF) and 1 mM L-citrulline. The homogenates were incubated for 30 min in the presence of 1 mM NADPH, 2 mM CaCl2 and 10 uM L-arginine containing 100.000 dpm of [2,3,4,5-H]L-arginine monohydrochloride (Amersham, UK) at room temperature (25–27°C). Pharmacological controls of enzymatic activity were also conducted without CaCl2 both to identify the type of NOS (addition of 1 mM EGTA, a Ca2+ influx inhibitor) and to selectively inhibit NOS (addition of 1 mM L-NAME). Protein content of the samples was determined by the Bradford Method [34] using a commercial kit (Bio Rad, Hercules, CA, USA). NOS activity was expressed as pmols L-citrulline produced per minute and per milligram of protein.

Protein expression of nNOS was also analyzed in homogenates of the hippocampus by the Western blot method using four pigeons per group. For total protein quantification, samples were homogenized in 1% Triton X-100, 50 mM phosphate buffer, pH 7.4, 1 mM sodium pyrophosphate, 1 mM sodium fluoride, 5 mM EDTA, 1 mM sodium vanadate, 1% protease inhibitor cocktail (P8340; Sigma), 7 M urea, and 2 M thiourea (10% w/v). Sample homogenization was carried out at 4°C using a Polytron 20 s generator set at maximum speed for 30 s. Insoluble materials were removed by centrifugation (12 000 g, 4°C, 15 min). Protein concentration was determined using the Bradford method [34]. One hundred milligrams of total protein extract from each animal was separated by SDS–polyacrylamide gel electrophoresis and electroblotted to a nitrocellulose membrane [35, 36]. Membranes were blocked with PBS–Tween containing 5% non-fat dry milk and then incubated with a rabbit polyclonal antibody to nNOS (NOS1 (R-20): sc 648, Santa Cruz Biotechnology, Santa Cruz, CA, USA) diluted (1:1000) in PBS–Tween containing 3% bovine serum albumin (12 h at 4°C). Membranes were washed with PBS–Tween and incubated with horseradish peroxidase–conjugated goat antibody to rabbit (1 : 10 000; Zymax, Zymed Laboratories, USA). The immunoreactive bands were detected by autoradiography on a Kodak GBX2 film using a SuperSignal West Pico chemiluminescent kit (Pierce, Rockford, IL, USA). Equal protein loading was assessed with Ponceau S staining of the membranes and optical density analysis of the various protein bands [37]. The optical density of the immunoreactive bands was determined by digital densitometry (Scion Image Software).

The enzymatic activity of Ca2+-dependent NOS and Ca2+-independent and optical densitometry data furnished by Western blot for nNOS expression were adjusted to a cosine curve [38] with a 24-hour period [39]. The data were analyzed using a one-way ANOVA, considering time as variable. The Tukey-Kramer test was used for post-hoc multiple comparisons.

Results

Figure 1 shows the enzymatic activity of cNOS (Figure 1A) and iNOS (Figure 1B) values for groups ZT0, ZT4, ZT8, ZT12, ZT16 and ZT20 in the hippocampus. Enzymatic activity was measured as the amount of L-citrulline produced in the reaction between NOS and L-arginine per minute and milligram of protein. The mean values for the absolute activity of cNOS were 0.65 ± 0.38 (ZT0); 0.96 ± 0.52 (ZT4); 0.71 ± 0.37 (ZT8); 0.52 ± 0.10 (ZT12); 0.59 ± 0.01 (ZT16) and 0.47 ± 0.22 (ZT20) and for iNOS the mean values were 0.83 ± 0.30 (ZT0); 0.95 ± 0.18 (ZT4); 0.16 ± 0.10 (ZT8); 0.33 ± 0.07 (ZT12); 0.25 ± 0.22 (ZT16); 0.47 ± 0.21 (ZT20). Figure 1A and 1B present data expressed as the ratio between the mean value of each group and the mean value of the ZT0 group. Statistical analysis with one-way ANOVA showed significant time differences for iNOS (F(5,18) = 5.93; p < 0.05) but not for cNOS (F(5,18) = 0.27; p > 0.05). Tukey-Kramer comparisons test showed that the ZT0 and the ZT4 groups had values of iNOS enzymatic activity that differed significantly from the ZT8, ZT12 and ZT16 groups (p < 0.05).
Figure 1

Enzymatic activity of cNOS and iNOS in hippocampus of pigeon. A- Mean values (+ s.e.m.) of the amount of L-citrulline (pmol/min/mg) produced by the reaction of the enzymatic activity of Ca2+ - dependent NOS (cNOS) in samples of hippocampal tissue homogenate. Data are expressed as ratio calculated relative to the mean of ZT0 group. One-way ANOVA. B- Mean values (+ s.e.m.) in the amount of L-citrulline (pmol/min/mg) produced by the reaction of the enzymatic activity of Ca2+ - independent NOS (iNOS) in samples of hippocampal tissue homogenate expressed as ratio relative to the mean of ZT0 group. One-way ANOVA indicated between group differences (p < 0.001); * indicates p < 0.05 when compared to ZT8, ZT12 and ZT16; # indicates p < 0.05 compared with ZT12 and (+ s.e.m.) ZT16 (Tukey-Kramer test; n = 4 pigeons per group).

Optical densitometry values of the nNOS immunoreactive bands (Figure 2A) were normalized for the total protein content of the samples as determined by Ponceau S solution for histochemical staining (Figure 2B). ANOVA indicated significant differences between groups (F(5,18) = 7.6; p < 0.05). Tukey-Kramer test showed that the ZT0 group differed significantly from the ZT12, ZT16 and ZT20 groups whereas the ZT4 group was significantly different from the ZT16 and ZT20 groups (p < 0.05).
Figure 2

Protein expression of nNOS in hippocampus of pigeon. A- Mean values (+ s.e.m.) of optical densitometric analyses of immunoreactive bands for nNOS in samples of hippocampal tissue homogenate normalized with Ponceau staining. Each mean was calculated with reference to the ZT0 value. The dashed line indicates the fitted curve by the Cosinor method. One-way ANOVA indicated group effects (p < 0.001); * indicates p < 0.05 when compared to ZT12, ZT16 and ZT20; # indicates p < 0.05 compared with ZT16 and ZT20 (Turkey-Kramer test; n = 4 pigeons per group). B- Representative immunoreactive bands for nNOS and proteins detected by Ponceau staining in each group.

Table 1 presents data on the rhythmic characteristics of iNOS enzymatic activity and nNOS protein content in the hippocampus that were obtained with the 24-hour Cosine Curve fit method (Cosana software [39]). The percent of rhythmic values obtained with the cosine curve analysis indicated oscillation of nNOS protein expression in the hippocampus. In addition, the cosine analysis also indicated oscillation of enzymatic activity of iNOS. The values of enzymatic activity of iNOS and nNOS protein content in the hippocampus showed significant rhythmicity (p < 0.05; Cosinor test).
Table 1

Parameters of the circadian rhythmicity in the enzymatic activity of iNOS and of nNOS protein expression, obtained by adjusting the cosine curve by method Cosinor (Benedito-Silva, 1988)

 

Acrophase

Bathyphase

Amplitude

Mesor

%R

P

iNOS activity

6 h36 a.m. ± 94 min

6 h36 p.m. ± 94 min

0,46 ± 0,19

0,29

52,10

0,001

nNOS content

9 h50 a.m. ± 38 min

9 h50 p.m. ± 38 min

0,24 ± 0,07

0,77

67,57

0,01

R% - Percent Rhythmic.

Acrophase - phase in which it is more likely to find the highest value of a sine curve set.

Mesor - average value of the fitted curve by the method Cosinor.

Discussion

The present results show that circadian oscillation of the nNOS protein expression and of the enzymatic activity of iNOS occurs in the hippocampus of pigeon. The oscillation of nNOS protein expression was more robust than that observed for iNOS activity as shown by higher percent rhythmic value for nNOS content than the percent rhythmic value for iNOS. The analysis of enzymatic activity values of cNOS did not show significant statistical differences between different time-points. However, the analysis with the cosine curve fit was indicative of daily oscillation of cNOS activity. We may conjecture that the statistical significance of the data was limited by the inter-individuals variability of the cNOS activity that was mainly observed at the time points during the subjective day, although the peak of cNOS enzymatic activity observed at ZT04 may have induced a detection of oscillation by the cosine analysis. The Cosinor procedure is considered to be adequate for detection of rhythmicity of molecular circadian oscillation in typical studies that use groups as small as 3 animals [40]. Our study used groups of 4 pigeons, but it can be considered that the use of more animals per group would improve the validity of the data. It is worth to note that the analysis of the activity of cNOS considers the activity of both eNOS and nNOS isoforms, whereas the analysis for the protein content refers only to nNOS. Thus, in each case the resulting rhythmicity was different, as demonstrated by the significant daily cycling in the hippocampus of pigeon only for expression of nNOS. In spite of this, we may consider that our results agree with the experimental evidence showing that the peak of NOS activity in the hippocampus and other brain regions of rats occurs during the activity phase [8, 9]. Additionally, since the nNOS protein accounts for the major part of NO production in the mammalian brain [2, 3], the present data can be considered as indirect evidence of circadian rhythm of NO signaling in the hippocampus of the pigeon.

The acrophase value of nNOS protein content occurred 9:50 a.m. ± 38 min in the hippocampus with a peak value around ZT4, during the activity phase and a trough value at ZT20, during the resting phase. Daily variation of NOS activity and protein levels have been described in the rat brain [8] and recent evidence showed that the oscillation of adenylyl ciclase and MAPK in the hippocampus is necessary for maintenance of hippocampal-dependent memory [15, 16]. The repeated reactivation of NMDA receptors and intracellular Ca2+ signaling leads to activation of the cAMP-MAPK-CREB pathway [1316] which has a central role in memory processes [15]. So, oscillations of NOS in the hippocampus may also contribute to processes of consolidation and maintenance of hippocampus-dependent memories.

In fact, nNOS activity in the central nervous system correlates with activation of NMDA receptors [41], which are widely localized in the hippocampus of both rodents [42] and pigeons [12]. Synaptic processes mediated by glutamate also triggers the activation of a signal transduction pathway which involves Glu- Ca2+/calmodulin-dependent kinase (Ca2+-CaMKII)-nNOS-GC-cGMP and clock genes transduction. Pharmacological inhibition of the nNOS or the cGMP-dependent kinase blocks the circadian responses to light in vivo [1]. Previous studies have demonstrated that processes related to cellular signaling involving nNOS induce changes in transcription of clock genes in the suprachiasmatic nucleus of rodents and are also involved with processes of synchronization and phase shift [1, 43, 44]. These results suggest a role of nNOS, and consequently NO, in the regulation of biological oscillators. However, it has yet to be determined how the expression of clock genes contributes to the maintenance of NOS oscillations in the hippocampus or vice-versa.

In addition, melatonin receptors in the hippocampus are coupled to inhibitory protein G [45, 46] and the inhibition of Ca2+ -mediated mechanisms by nocturnal melatonin could explain NOS oscillation in the hippocampus. Accordingly, lesion in the SCN blocked the circadian oscillation of Ca2+ stimulated adenylyl ciclase and MAPK activities in the hippocampus of mice, suggesting that the SCN function is required for the molecular circadian oscillation in the hippocampus [16]. These findings indicate that the SCN can indirectly modulate Ca2+ stimulated adenylyl ciclase in the hippocampus during the circadian cycle by controlling the release of melatonin from the pineal gland, which is a major efferent pathway of the biological timing system [47]. The expression and activity of both nNOS and iNOS proteins may be dependent on circadian timing system and according to recent evidence melatonin may be involved in the regulation of these mechanisms [4850]. A transient but substantial rise of the constitutive nNOS was observed when cultured cells were incubated during 6 hours with 1 nM melatonin volume [50]. On the other hand, high plasmatic melatonin concentration was shown to inhibit the expression of both nNOS and iNOS [48, 49, 51, 52]. In birds, both pineal and retinal melatonin have also an important role in the control of avian circadian rhythms [20, 23]. A robust light–dark rhythm of melatonin was detected in pigeons, with low plasma melatonin in the light phase. The nocturnal peak was observed at 03:00 h with values 100–300 pg/ml of circulating melatonin [53]. In the present study, the peak of nNOS expression was observed around 10 a.m., that is, it occurred around seven hours after the peak of melatonin reported by the previous study on melatonin rhythm in pigeons conducted in our laboratory [53]. So, these results are consistent with the findings on the temporal expression of nNOS mRNA in in vitro study with human cells [50].

These findings in diurnal animals make intriguing relationship of melatonin and NOS in nocturnal animals, since the pace of both NOS activity and melatonin in rodents have peaks during the dark phase [8, 9, 54, 55]. The experimental evidence collected in mammals showing cNOS diurnal oscillation is scarce and related with nocturnal rodents, as is seen in the studies reported by Ayers et al.[8] and Tuçtan et al.[9]. Besides, to the extent of our knowledge, our results provide the first description of daily rhythmicity of nNOS protein content in the hippocampus of the pigeon. So, more investigations are still needed for comparisons of the phase relationship of the curves of melatonin and NOS in other diurnal and nocturnal species. Nevertheless, it is reasonable to consider the occurrence of the peak of nNOS protein content in the hippocampus during the light phase of a diurnal animal, such as the pigeon, since during the activity phase of diurnal animals there is a requirement for high processing of environmental information that results in learning and memory, and, additionally, these processes are fundamentally related with the nNOS activity in the brain. Accordingly, it may not be surprising that nocturnal and diurnal animals exhibit daily oscillation of biological variables with peaks occurring at different circadian phases. In this sense, it may reasonable to consider that this fact can also be related with the higher variability of cNOS enzymatic activity during the subjective day.

Different NOS isoforms are considered to play distinct roles in the CNS. The nNOS isoform has been pointed as the major NOS isoform that is essentially involved with enhancement of memory formation and consolidation [56, 57], although eNOS has been also indicated to participate in processes of memory formation [58]. Although the nNOS activity in the hippocampus is a key factor for learning and memory processes, Rappanelli et al.[59] showed that both eNOS and nNOS activities in the prefrontal cortex and hippocampus were augmented during the operant learning process in rats. Besides, exposures to uncontrollable or severe stressors induced nNOS expression in brain structures including the hippocampus, amygdala and cortex [59] and there is evidence indicating that increased production of NO in the dorsolateral periaqueductal gray area is involved in the anxiety behavior displayed by rats [60]. Additionally, both nNOS and iNOS participate of mechanisms related with neurogenesis in the hippocampus, since decreases in nNOS activity or increases in iNOS expression have been reported to promote neurogenesis in the dentate gyrus [5760]. Besides, it is assumed that there is an inverse relation between increases in the systemic expression of iNOS and the amount of encephalic nNOS [61], although the mechanism regulating this relation still needs better comprehension. Though iNOS has been noted for its role in the brain defense mechanisms and deleterious processes, there are evidence of increased expression of iNOS in the hippocampus after training in spatial memory tasks [62, 63], which draws attention to its possible role in mechanisms of learning and memory formation [63].

Therefore, the present data demonstrate that an oscillation in iNOS activity and nNOS protein content occurs in the hippocampus of pigeons. These observations extend the evidence of molecular cycling in the hippocampus to the avian hippocampus and may be seen as directly related to reports on the relationship between the circadian system and the molecular mechanisms of learning and memory [64, 65]. Furthermore, these observations extend the knowledge on the similarities between the neurochemical, intrinsic and extrinsic organizational and functional characteristics of the avian and mammalian hippocampus [12, 6668].

Declarations

Acknowledgments

This research received financial support from Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP; 2010/09111-1). A.V.M.N. was recipient of a fellowship from FAPESP (2008/08788-8).

Authors’ Affiliations

(1)
Departamento de Biologia Estrutural e Funcional, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP)
(2)
Departamento de Farmacologia, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP)

References

  1. Golombek DA, Agostino PV, Plano SA, Ferreyra GA: Signaling in the mammalian circadian clock: the NO/cGMP pathways. Neurochem Int 2004, 45:929–936.PubMedView ArticleGoogle Scholar
  2. Brendt DS, Hwang PM, Snyder SH: Localization of nitric oxide synthase indicating a neural role of nitric oxide. Nature 1990, 347:768–770.View ArticleGoogle Scholar
  3. Salter M, Knowles RG, Moncada S: Widespread tissue distribution, species distribution and changes in activity of Ca(2+)-dependent and Ca(2+)-independent nitric oxide synthases. FEBS lett 1991,291(1):145–149.PubMedView ArticleGoogle Scholar
  4. Brendt DS, Snyder SH: Nitric oxide mediates glutamate-linked enhancement of cGMP levels in the cerebellum. PNAS 1989, 89:9030–9033.View ArticleGoogle Scholar
  5. Garthwaite J: Glutamate, nitric oxide and cell–cell signalling in the nervous system. Trends Neurosci 1991, 14:60–67.PubMedView ArticleGoogle Scholar
  6. Choi YB, Tenneti L, Le DA, Ortiz J, Bai G, Chen HS, Lipton SA: Molecular basis of NMDA receptor-coupled ion channel modulation by S-nitrosylation. Nat Neurosci 2000, 3:15–21.PubMedView ArticleGoogle Scholar
  7. Micheva KD, Holz RW, Smith SJ: Regulation of presynaptic phosphatidylinositol 4,5-biphosphate by neuronal activity. J Cell Biol 2001, 154:355–368.PubMedView ArticleGoogle Scholar
  8. Ayers NA, Kapás L, Krueger JM: Circadian variation of nitric oxide synthase activity and cytosolic protein levels in rat brain. Brain Res 1996, 707:127–130.PubMedView ArticleGoogle Scholar
  9. Tunçtan B, Weigl Y, Dotan A, Peleg L, Zengil H, Ashkenazi I, Abacioclu N: Circadian variation of nitric oxide synthase activity in mouse tissue. Chronobiol Int 2002,19(2):393–404.PubMedView ArticleGoogle Scholar
  10. Rogers LJ: The molecular neurobiology of early learning, development, and sensitive periods, with emphasis on the avian brain. Mol Neurobiol 1993,7(3–4):161–187.PubMedView ArticleGoogle Scholar
  11. Székely AD: The avian hippocampal formation: subdivisions and connectivity. Behav brain Res 1999,98(2):219–225.PubMedView ArticleGoogle Scholar
  12. Rosinha MU, Ferrari EAM, Toledo CA: Immunohistochemical distribution of AMPA-type label in the pigeon (C. livia) hippocampus. Neuroscience 2009,159(2):438–450.PubMedView ArticleGoogle Scholar
  13. Cui Z, Wang H, Tan Y, Zaia KA, Zhang S, Tsien JZ: Inducible and reversible NR1 knockout reveals crucial roles of the NMDA receptor preserving in remote memories in the brain. Neuron 2004,41(5):781–793.PubMedView ArticleGoogle Scholar
  14. Lee AK, Wilson MA: Memory of sequential experience in the hippocampus during slow wave sleep. Neuron 2002, 36:1183–1194.PubMedView ArticleGoogle Scholar
  15. Eckel-Mahan KL, Phant T, Han S, Wang H, Chan GC-K, Scheiner ZS, Storm DR: Circadian oscillation of hippocampal MAPK activity and cAMP: implications of memory persistence. Nat Neurosci 2008, 11:1074–1082.PubMedView ArticleGoogle Scholar
  16. Phan TX, Chan GC, Sindreu CB, Eckel-Mahan KL, Storm DR: The diurnal oscillation of MAP (mitogen-activated protein) kinase and adenylyl cyclase activities in the hippocampus depends on the suprachiasmatic nucleus. J Neurosci 2011,20;31(29):10640–10647.View ArticleGoogle Scholar
  17. Böhme GA, Bon C, Stutzmann JM, Doble A, Blanchard JC: Possible involvement of nitric oxide in long-term potentiation. Eur J Pharmacol 1991, 199:379–381.PubMedView ArticleGoogle Scholar
  18. O’Dell TJ, Hawkins RD, Kandel ER, Arancio O: Tests of the roles of two diffusible substances in long-term potentiation: evidence for nitric oxide as a possible early retrograde messenger. Proc Natl Acad Sci U S A 1991, 88:11285–11289.PubMedView ArticleGoogle Scholar
  19. Doyle C, Hölscher C, Rowan MJ, Anwyl R: The selective neuronal NO synthase inhibitor 7-nitro-indazole blocks both long-term potentiation and depotentiation of field EPSPs in rat hippocampal CA1 in vivo. J Neurosci 1996,16(1):418–424.PubMedGoogle Scholar
  20. Gwinner E, Hau M, Heigl S: Melatonin: generation and modulation of avian circadian rhythms. Brain Res Bull 1997,44(4):439–444.PubMedView ArticleGoogle Scholar
  21. Nichelmann M, Höchel J, Tzschentke B: Biological rhythms in birds–development, insights and perspectives. Comp Biochem Physiol A Mol Integr Physiol 1999,124(4):429–437.PubMedView ArticleGoogle Scholar
  22. Oishi T, Yamao M, Kondo C, Haida Y, Masuda A, Tamotsu S: Multiphotoreceptor and multioscillator system in avian circadian organization. Microsc Res Tech 2001,53(1):43–47.PubMedView ArticleGoogle Scholar
  23. Cassone VM, Paulose JK, Whitfield-Rucker MG, Peters JL: Time’s arrow flies like a bird: two paradoxes for avian circadian biology. Gen Comp Endocrinol 2009,163(1–2):109–116.PubMedView ArticleGoogle Scholar
  24. Rashotte ME, Basco PS, Henderson RP: Daily cycles in body temperature, metabolic rate, and substrate utilization in pigeons: influence of amount and timing of food consumption. Physiol & Behav 1995,57(4):731–746.View ArticleGoogle Scholar
  25. Basco PS, Rashotte ME, Stephan FK: Photoperiod duration and energy balance in the pigeon. Physiol & Behav 1996,60(1):151–159.View ArticleGoogle Scholar
  26. Rashotte ME, Saarela S, Henderson RP, Hohtola E: Shivering and digestion-related themogenesis in pigeons during dark phase. Am J Physiol Regul Integr Comp Physiol 1999, 277:R1579-R1587.Google Scholar
  27. Wu WQ, McGoogan JM, Cassone VM: Circadian regulation of visually evoked potentials in the domestic pigeon, Columba livia . J Biol Rhythms 2000, 15:317–328.PubMedView ArticleGoogle Scholar
  28. Siqueira LO, Vieira AS, Ferrari EAM: Time-of-day variation in the sensitization of the acoustic response in pigeons. Biol Rhythm Res 2005,36(1/2):151–157.View ArticleGoogle Scholar
  29. Valentinuzzi VS, Ferrari EAM: Habituation to sound during morning and night sessions in pigeons ( Columba livia ). Physiol and Behav 1997,62(6):1203–1209.View ArticleGoogle Scholar
  30. Herold C, Diekamp B, Güntürkün O: Stimulation of dopamine D1 receptors in the avian fronto-striatal system adjusts daily cognitive fluctuations. Behav Brain Res 2008, 194:223–229.PubMedView ArticleGoogle Scholar
  31. Petruso EJ, Fuchs T, Bingman VP: Time-space learning in homing pigeons ( Columba livia ): orientation to an artificial light source. Anim cogn. 2007, 10:181–188.PubMedView ArticleGoogle Scholar
  32. Karten HJ, Hodos W: A stereotaxic atlas of the brain of the pigeon (Columba livia). Baltimore, Maryland: The Johns Hopkins Press; 1967.Google Scholar
  33. Faria MS, Muscará MN, Moreno-Júnior H, Teixeira SA, Dias HB, De Oliveira B, Graeff FG, De Nucci G: Acute inhibition of nitric oxide synthesis induces anxiolysis in the plus maze test. Eur J Pharmacol 1997,323(1):37–43.PubMedView ArticleGoogle Scholar
  34. Bradford MM: A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye biding. Anal Biochem 1976, 72:248–254.PubMedView ArticleGoogle Scholar
  35. Laemmli UK: Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature 1970,227(5259):680–685.PubMedView ArticleGoogle Scholar
  36. Towbin H, Staehelin T, Gordon J: Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proc Natl Acad Sci U S A 1979,76(9):4350–4354.PubMedView ArticleGoogle Scholar
  37. Romero-Calvo I, Ocón B, Martinéz-Moya P, Suaréz MD, Zarzuelo A, Martinéz-Augustin O, Medina FS: Reversible Ponceau staining as a loading control alternative to actin in Western Blots. Anal Biochem 2010,401(2):318–320.PubMedView ArticleGoogle Scholar
  38. Nelson W, Tong YL, Lee JK, Halberg F: Methods for Cosinor Rhythmometry. Chronobiologia 1979, 6:305–323.PubMedGoogle Scholar
  39. Benedito-Silva AA: Cosana: uma versão atualizada do Cosina para microcomputador de 16 bits [abstract]. In III Reunião Anual da Federação das Sociedades de Biologia Experimental, 1988, Caxambu. Caxambu: Caxambu. Programa e Resumos da III Reunião annual da federação das sociedades de biologia experimental; 1988:46.Google Scholar
  40. Refinetti R, Cornélissen G, Halberg F: Procedures for numerical analysis of circadian rhythms. Biol Rhythm Res 2007,38(4):275–325.PubMedView ArticleGoogle Scholar
  41. Garthwaite J, Boulton CL: Nitric oxide signaling in the central nervous system. Annu Rev Physiol 1995, 57:683–706.PubMedView ArticleGoogle Scholar
  42. Monaghan DT, Cotman CW: Distribution of N-Methyl-D-aspartate-sensitive L-[3H] Glutamate-binding Sites in Rat Brain. J Neuroscience 1985,5(11):2909–2919.Google Scholar
  43. Agostino PV, Plano AS, Golombek DA: Sildenafil acselerates reentrement of circadian rhythms after advancing light schedules. PNAS 2007,104(23):9834–9839.PubMedView ArticleGoogle Scholar
  44. Plano SA, Agostino PV, Golombek DA: Extracellular nitric oxide signaling in the hamster biological clock. FEBS letters 2007, 581:5500–5504.PubMedView ArticleGoogle Scholar
  45. Von Gall C, Stehle JH, Weaver DR: Mammalian melatonin receptors: molecular biology and signal transduction. Cell Tissue Res 2002, 309:151–162.PubMedView ArticleGoogle Scholar
  46. Wang LM, Suthana NA, Chaudhury D, Weaver DR, Colwell CS: Melatonin inhibits hippocampal long-term potentiation. Eur J Neurosci 2005,22(9):2231–2237.PubMedView ArticleGoogle Scholar
  47. Yamanaka Y, Suzuki Y, Todo T, Honma K, Honma S: Loss of circadian rhythm and light-induced suppression of pineal melatonin levels in Cry1 and Cry2 double-deficient mice. Genes Cell 2010,15(10):1063–1071.View ArticleGoogle Scholar
  48. Léon J, Marcias M, Escames G, Camacho E, Khaldy H, Martin M, Espinosa A, Gallo MA, Acuña-Castroviejo D: Structure-related inhibition of calmodulin-dependent neuronal nitric oxide synthase activity by melatonin and synthase activity by melatonin and synthetic kynurenines. Mol Pharmacol 2000,58(5):967–975.PubMedGoogle Scholar
  49. Koh PO: Melatonin regulates nitric oxide synthase expression in ischemic brain injury. J Vet Med Sci 2008,70(7):747–750.PubMedView ArticleGoogle Scholar
  50. Arese M, Magnifico MC, Mastronicola D, Altieri F, Grillo C, Blanck TJ, Sarti P: Nanomolar melatonin enhances nNOS expression and controls HaCaT-cells bioenergetics. IUBMB Life 2012,64(3):251–258.PubMedView ArticleGoogle Scholar
  51. Léon J, Escames G, Rodríguez MI, López LC, Tapias V, Entrena A, Camacho E, Carrión MD, Gallo MA, Espinosa A, Tan DX, Reiter RJ, Acuña-Castroviejo D: Inhibition of neuronal nitric oxide synthase activity by N1-acetyl-5-methoxykynuramine, a brain metabolite of melatonin. J Neurochem 2006,98(6):2023–2033.PubMedView ArticleGoogle Scholar
  52. Camacho ME, Carrion MD, Lopez-Cara LC, Entrena A, Gallo MS, Espinosa A, Escames G, Acuña-Castroviejo D: Melatonin synthetic analogs as nitric oxide synthase inhibitors. Mini Rev Med Chem 2012,12(7):600–617.PubMedView ArticleGoogle Scholar
  53. Souza CMZ, Silva AAMR, Caldas MCS, Valentinuzzi VS, Ferrari EAM: Diurnal Variation of plasmatic melatonin, corticosterone and variation of general activity in pigeons under light–dark cycle and constant light. Biological Rhythms research 2001,32(2):243–254.Google Scholar
  54. Golombek DA, Escolar E, Burin LJ, Sánchez MGB, Cardinali DP: Time-dependent melatonin analgesia in mice: inhibition by opiate or benzodiazepine antagonism. Eur J Pharmacol 1991, 194:25–30.PubMedView ArticleGoogle Scholar
  55. Binkley SA: Circadian rhythms of pineal function in rats. Endocr Rev 1983,4(3):255–270.PubMedView ArticleGoogle Scholar
  56. Komsuoglu-Celikyurt I, Gocmez SS, Mutlu O, Aricioglu F, Utkan T: Evidence for the involvement of neuronal nitric oxide synthase and soluble guanylate cyclase on cognitive functions in rats. Life Sci 2011,89(23–24):905–910.PubMedView ArticleGoogle Scholar
  57. Utkan T, Gocmez SS, Ozer C, Gacar N, Aricioglu F: Selective and nonselective neuronal NOS inhibitors impair cognitive function in the three panel runway and passive avoidance tasks in rats. Pharmacol Biochem Behav 2012,101(4):515–519.PubMedView ArticleGoogle Scholar
  58. Rapanelli M, Frick LR, Zanutto BS: Modulation of endothelial and neuronal nitric oxide synthases during learning of an operant task. J Neurochem 2010, 113:725–734.PubMedView ArticleGoogle Scholar
  59. Oliveira RM, Guimarães FS, Deakin JF: Expression of neuronal nitric oxide synthase in the hippocampal formation in affective disorders. Braz J Med Biol Res 2008,41(4):333–341.PubMedView ArticleGoogle Scholar
  60. Tonetto LL, Terzian AL, Del Bel EA, Guimarães FS, Resstel LB: Inhibition of the NMDA receptor/Nitric Oxide pathway in the dorsolateral periaqueductal gray causes anxiolytic-like effects in rats submitted to the Vogel conflict test. Behav Brain Funct 2009, 5:40–47.PubMedView ArticleGoogle Scholar
  61. Eckel B, Ohl F, Bogdanski R, Kochs EF, Blobner M: Cognitive deficits after systemic induction of inducible nitric oxide synthase: a randomised trial in rats. Eur J Anaesthesiol 2011,28(9):655–663.PubMedView ArticleGoogle Scholar
  62. Cavallaro S, D’Agata V, Manickam P, Dufour F, Alkon DL: Memory-specific temporal profiles of gene expression in the hippocampus. PNAS 2002, 99:16279–16284.PubMedView ArticleGoogle Scholar
  63. Gökçek-Saraç Ç, Karakurt S, Adali O, Jakubowska-Dogru E: Correlation between hippocampal levels of neuronal, epithelial and inducible NOS and spatial learning skills in rats. Behav Brain Res 2012, 235:326–333.PubMedView ArticleGoogle Scholar
  64. Eckel-Mahan KL, Storm DR: Circadian rhythms and memory: not to simple as cogs and gears. EMBO rep 2009,10(6):584–591.PubMedView ArticleGoogle Scholar
  65. Ruby NF, Hwang CE, Wessells C, Fernandez F, Zhang P, Sapolsky R, Heller G: Hippocampal-dependent learning requires a functional circadian system. PNAS 2008,105(40):15593–15598.PubMedView ArticleGoogle Scholar
  66. Atoji Y, Wild JM, Yamamoto Y, Suzuki Y: Intratelencephalic connections of the hippocampus in pigeons ( Columba livia ). J Comp Neurol 2002, 447:177–199.PubMedView ArticleGoogle Scholar
  67. Brito I, Britto LR, Ferrari EAM: Classical tone-shock conditioning induces Zenk expression in the pigeon ( Columba livia ) hippocampus. Behav Neurosci 2006,120(2):353–361.PubMedView ArticleGoogle Scholar
  68. Kahn MC, Hough Ii GE, Bingman VP: Internal connectivity of the homing pigeon ( Columba livia) hippocampal formation: an anterograde and retrograde tracer study. J Comp Neurol 2002, 459:127–141.View ArticleGoogle Scholar

Copyright

© Machado-Nils et al.; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Advertisement