Circadian rhythm of body temperature persists after suprachiasmatic lesions in the squirrel monkey

Abstract

Squirrel monkeys (Saimiri sciureus) demonstrate prominent circadian (approx 24 h) rhythms in many behavioral and physiological variables including drinking and body temperature. Both of these rhythms can be entrained by a 24-h light-dark cycle (LD 12:12) but will free-run with an endogenous period in a constantly illuminated (LL:600 lx) environment free of time cues. After radio-frequency lesions were placed stereotaxically in the suprachiasmatic nuclei (SCN) of five monkeys, the circadian rhythm of drinking behavior was disrupted when the monkeys were maintained in LL. However, the circadian rhythm in core body temperature in these animals persisted in LL with a significant circadian spectral component following destruction of the SCN. The SCN thus appear to be of fundamental importance for regulating the circadian organization of drinking; however, an oscillator located elsewhere in the squirrel monkey is capable of generating the core body temperature rhythm.

The Retinohypothalamic Projection and Oxidative Metabolism in the Suprachiasmatic Nucleus of Primates and Tree Shrews

“…The pattern of retinal projection to the hypothala mus in tree shrews found in this study is consistent with patterns found in previous studies [Moore, 1973;Conrad and Stumpf, 1975;Fuller et al, 1981]. The ret inal projection to the hypothalamus in tree shrews ex hibited several anatomical differences from that of primates.…”

“…The LASCN is also present in primates, suggesting that the neural region involved in circa dian functions may extend significantly beyond the neural borders of the SCN. Several studies have dem onstrated that lesions of the SCN do not result in the complete disruption of temperature [Fuller et al, 1981] and cortisol rhythms [Reppert et al, 1981] LASCN may be involved in circadian function. This interpretation is supported by developmental studies that have demonstrated that the CyOX development of the LASCN [Murakami and Fuller, 1988] coincides with the late postnatal development of temperature [Kittrel and Satinoff, 1986] and cortisol rhythms [Allen and Kendel, 1967;Itoh and Hirota, 1976] in rats.…”

Effects of Corticotropin-Releasing Factor and Growth Hormone-Releasing Factor on Sleep and Activity in Rats

“…As seen in Figure I, CRF at the 0.0015 nmol dose produced a spectral pattern characterized by de creases in the 1-2, 2-4 and 4-6 Hz bands, and increases in 32-64 Hz activity in the cortical leads. The higher dose of CRF (0.015 nmol) produced significant decreases in [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Hz and increases in the 32-64 Hz band.…”

“…ICV administration of GRF was also found to produce decreases in locomotion when administered during the active part of the rats' circadian cycle. These EEG and behavioral findings seen following CRF and GRF are consistent with the behaviors frequently correlated with the known circadian timing of the release of corticosteroids and growth hormone during the sleep-waking cycle in rat and human.Evidence that a hypothalamic site may participate in the timing or the onset of sleep or wakefulness is supported by studies in rats [30] as well as in diurnal primates [16], where lesions in the suprachiasmatic nucleus have been shown to shift or disrupt free-running rest-activity rhythms. How such a hypothalamic clock or pacemaker may transduce event timing into the behavioral state transitions of the sleep-wake cycle is unclear; however, a humoral messenger either neural or endocrine seems likely.…”

Effects of simian immunodeficiency virus on the circadian rhythms of body temperature and gross locomotor activity

“…Studies carried out in squirrel monkeys suggest the existence of two separate self-sustained oscillators (44,45). In these studies, SCN lesions disrupted the rhythm of behavioral activity without affecting the body temperature rhythm, whereas manipulation of the light/dark cycle resulted in desynchronization between the acrophases of the body temperature and locomotor activity.…”