Role of the locus coeruleus in transmission onto anterior colliculus neurons

Abstract

The present study was an attempt to elucidate the role of locus coeruleus (LC) on neuronal activities in the anterior colliculus of rats anesthetized with α-chloralose. The spike latency of neurons in the deep grey and white layers of anterior colliculus elicited by stimulation of the optic chiasm (OC), lateral geniculate body (LGB) and visual cortex (VC) was longer than that of neurons in the more superficial layers: optic and intermediate grey layers. When conditioning stimuli were applied to LC, a significant inhibition of spike generation upon OC, LGB and VC stimulation was observed on neurons of deep grey and white layers, but not on those of optic and intermediate grey layers. The conditioning stimulation did not alter spike generation, either in the neurons of deep grey and white layers or those of optic and intermediate grey layers, following stimulation of the superficial grey layer. These results strongly suggest that noradrenaline originating in the LC could produce an inhibition of neuronal activities in the deep grey and white layers, and such is probably the result of inhibition of neurons located in the superficial layer of the anterior colliculus.