The action of norepinephrine in the rat hippocampus. III. Hippocampal cellular responses to locus coeruleus stimulation in the awake rat.

The behavioral and physiological effects of electrical stimulation of the nucleus locus coeruleus (LC) were studied in the awake rat. LC electrodes consistently supported high rates of self-stimulation (SS). LC stimulation also inhibited spontaneous cellular discharges in the hippocampus (HPC). Both the LC-induced inhibition of HPC units and the LC-evoked SS behavior were antagonized by alpha-methyltyrosine and 6-hydroxydopamine. In addition, chlorpromazine and diethyldithiocarbamate antagonized LC-induced inhibition of HPC units. D-Amphetamine facilitated SS behavior and reduced spontaneous HPC unit activity. The reinforcing properties of LC stimulation correlate closely with inhibition of cellular activity in the hippocampus; both actions appear to be mediated by norepinephrine.