Figure 34

Circadian rhythm alteration rather than obliteration after lesioning of suprachiasmatic nuclei (SCN). By eyeballing alone of Section IIA, the circadian rhythm in telemetered core temperature, each measurement shown by a dot, is clearly seen in data from a sham-operated control on the left and seems to be lost in the rat with a SCN lesion on the right of this section, whether one examines squeezed values in the top row or stretched values in the second row (of dots). A circadian rhythm in temperature for individual animals is also displayed in Section I top, with a smaller within-day change of lesioned animals (IB) as compared to controls (IA). This finding is also seen after averaging in Section IIB (bottom). Microscopy, in section IIC, apart from quantifying the rhythm by cosinor, reveals, by a shorter arrow, a great amplitude lowering after a bilateral SCN ablation and a phase advancement seen as an earlier vector. Section IIC also validates the persisting rhythm by the non-overlap of the center (or pole) of the graph, by the error ellipse representing a 95% confidence region: the removal of the SCN is compatible with the persistence of a statistically highly significant circadian rhythm in core temperature quantified with its parameters and their uncertainties, after histologically validated bilateral SCN ablation. When the ablation unintentionally, as discovered at post-mortem, was unilateral (U), the circadian amplitude was enhanced (Section I, bottom), a finding suggesting a subtractive coupling between the two SCN. Section III is in keeping with the speculation of an effect by lunar factors upon the "free-running" (or rather lunar?) period of about 24.8 hours found in controls or unilaterally ablated animals at that light intensity. If this should be in part a lunar effect, it is lost in animals subjected to bilateral (B) suprachiasmatic lesions and apparently tightened by unilateral (U) lesions, a possibility requiring further experimental scrutiny.