Journal of Neuroscience, Vol 1, 1414-1425, Copyright © 1981 by Society for Neuroscience
Effects of damage to the suprachiasmatic area of the anterior hypothalamus on the daily melatonin and cortisol rhythms in the rhesus monkey
SM Reppert, MJ Perlow, LG Ungerleider, M Mishkin, L Tamarkin, DG Orloff, HJ Hoffman and DC Klein
The effects of lesions of the suprachiasmatic nucleus (SCN) on the
circadian rhythms in melatonin and cortisol were examined in the rhesus
monkey. The concentrations of the two hormones were monitored in
cerebrospinal fluid (CSF) withdrawn from two sham-operated animals, two
animals with complete bilateral SCN lesions, and two animals with partial
SCN damage at 4 and 8 months after surgery. In the sham- operated animals,
as in the intact animal, the daily melatonin rhythm was entrained to the
daily light-dark cycle, was suppressed in constant light, and persisted in
constant darkness. In contrast, neither animal with complete SCN ablation
exhibited a daily pattern of CSF melatonin in diurnal lighting at 4 months
after surgery nor were their melatonin levels at constant low values.
Furthermore, CSF melatonin concentrations were not suppressed in either
animal by constant light. Surprisingly, at 8 months after surgery, spectral
analysis revealed a 24-hr component to the melatonin patterns for each
animal with complete SCN ablation in both diurnal lighting and constant
darkness. The two animals with partial SCN damage exhibited a daily
melatonin rhythm in diurnal lighting, but constant light did not suppress
CSF melatonin concentrations consistently. Daily rhythms persisted in both
for a 6 1/2-d period of study in constant darkness. In contrast to the
alterations in the melatonin rhythm after SCN damage, there was no apparent
effect of either partial or complete SCN ablation on the daily CSF cortisol
rhythm. These data indicate that, in the rhesus monkey, the SCN is
important for the generation, photic entrainment, and photic suppression of
the melatonin rhythm. However, circadian oscillators located outside of the
SCN region may control the normal daily cortisol rhythm and perhaps the
melatonin rhythm in the absence of the SCN.
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