Sleep state-specific neuronal activity in rat dorsal lateral geniculate nucleus is not altered by local serotonin and norepinephrine depletion

Abstract

The relay cells in dorsal lateral geniculate nucleus (dLGN) represent one among many populations of neurons throughout the neuraxis that display systematic alteration of spontaneous rate and pattern of discharge concurrent with change in state of arousal. Both noradrenergic (NE) and serotonergic (5-HT) systems innervate dLGN and are implicated in sleep-wake control mechanisms. Our study was designed to test the influence of these systems upon sleep state-related multiple unit activity in the dLGN. Two monoamine neurotoxins, 5,7-dihydroxytryptamine and 6-hydroxydopamine, were injected locally into dLGN to destroy NE and 5HT afferents individually and in combination. In three separate treatment groups, mean monoamine concentrations in dLGN were reduced in relation to the contralateral, vehicle-injected, control dLGN to: 1) NE-17%, 5HT-14%; 2) NE-46%, 5HT-28%, and 3) NE-6%, 5HT-77%. In no case was chronic sleep state-related cell activity in dLGN significantly altered. We conclude that afferent monoaminergic inputs are not critically related to the mechanisms underlying normative shifts in sleep state-related neuronal activity in dLGN.