ABSTRACT
The circadian rhythm of body temperature (CRT) is a robust marker of the endogenous pacemaker function and is one of the most frequently studied rhythms. Melatonin, the main secretion of the pineal gland seems to have more of a thermomodulatory role in controlling the body temperature than having a direct role in thermoregulation. The sympathetic innervation to the pineal via the superior cervical ganglion determines the melatonin secretion, and superior cervical ganglionectomy (SCGx) decreases the secretion of melatonin. The present study was conducted on the Wistar rats (n = 12) to determine the role of melatonin in modulation of CRT. Adult male rats were either ganglionectomised (n = 6) or sham ganglionectomised (n = 6). Rectal temperature was recorded for CRT analysis. Cosinar analysis of the temperature record was done to get the acrophase, amplitude and mesor. Our results show that SCGx decreases the amplitude to the rhythm but has no effect on the mesor of the rhythm. Our study confirms that melatonin has little role to play in the thermoregulation and its role is mainly in thermomodulation.