A Noradrenaline-Induced Inhibition from Locus Coeruleus of Nucleus Accumbens Neuron Receiving Input from Hippocampus

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Abstract
Electrophysiological studies using rats anesthetized with chloral hydrate were performed to determine whether or not noradrenaline originating in the locus coeruleus (LC) produces a beta-receptor-mediated inhibition of the nucleus accumbens (Acc) neurons receiving input from the hippocampus (HPC). When conditioning stimuli were applied to the LC preceding a test stimulus to the HPC, an inhibition of spike generation with HPC stimulation was observed during 20-100 msec of the conditioning-test time interval. This inhibition was observed when the stimulating electrode was located in the LC or its immediate vicinity. The spike generation upon HPC stimulation was also inhibited by iontophoretic application of noradrenaline, and the inhibition was antagonized by ionotophoretically applied sotalol, a beta-adrenergic blocker, but not by phentolamine, an alpha-adrenergic blocker. These results suggest that noradrenaline derived from the LC produces a beta-receptor-mediated inhibition of the Acc neurons receiving input from the HPC.