Circadian rhythms in synaptic excitability of the dorsal lateral geniculate nucleus in the rat

Excitability changes of the dorsal lateral geniculate nucleus were recorded in male albino rats (Wistar strain) with chronically implanted electrodes. Both averaged postsynaptic and presynaptic evoked responses showed clear circadian rhythms under a constant dark condition. The circadian rhythmicity of the evoked responses was not as a result of motor activity or due to the sleep-wakefulness changes which might show circadian rhythms independently. Circadian rhythms of antidromic and orthodromic evoked responses were abolished after bilateral suprachiasmatic nucleus lesions. These results suggest that the circadian rhythm generated in the suprachiasmatic nucleus significantly affects visual information transmission in the lateral geniculate nucleus.