Figure 35

Persistent, albeit altered, circadian rhythmicity of ³H-TdR incorporation into DNA of different organs and of mitotic index of corneal epithelium of BD₂F₁ female mice after bilateral lesioning of suprachiasmatic nuclei (SCN) (rows 1–3); persistence of altered rhythm seen in ethanol (row 4; left) but not water (row 4; right) consumption after bilateral lesioning. Data from JN Pasley (Advances in Chronobiology. JE Pauly and LE Scheving, eds. Alan R Liss, Inc. New York, Part B, pp 467–471, 1987). The SCN coordinates a collateral hierarchy that can be quantified in terms of amplitude and phase: the major effect of bilateral SCN ablation is thus far invariably, comparably to the behavior of core temperature in Fig. 34, an advance in phase for the SCN-lesioned (L) animals in 8 cases out of 8, with a reduction in amplitude, except for DNA labelling in the stomach and colon, which may respond to food directly rather than by the SCN, Section III. Section VI shows a microscopic phase and amplitude chart summarizing the finding in the other sections (I-V, VII and VIII). This chart extends the scope of the lesson learned in Fig. 34 to a number of variables other than core temperature, studied as marker rhythm: rather than being a master clock leading to the loss of all rhythms when ablated bilaterally, the SCN is compatible with the rhythm's persistence in several of the variables investigated, except for water-drinking blood pressure and locomotor activity [201]. A subjective time-macroscopic interpretation-based impression, that led to the master clock illusion is replaced by the objective quantification of a mechanism for period, phase and amplitude in a network [15].