[Effects of stimulation of locus coeruleus on cardiac contractility and renal nerve activity]

Experiments were performed on 64 cats anesthetized with chloralose-urethane, paralyzed and artificially ventilated. Electrical stimulation of locus coeruleus (LC) elicited increases in BP, HR, LVSP, dP/dt max and RNA. Buffer nerve section had no effect on the increase of these parameters, but could prolong the time of rise of BP and recovery phases. Injection of L-glutamate into LC, on the other hand, could decrease BP, HR, LVSP and dP/dt max. Intra-LC injection of kainic acid could also decrease BP. When the LC neurons showed degeneration or depolarization block after kainic acid injection, electrical stimulation of the LC could still elicit marked pressor response. The results suggest that the pressor response induced by electrical stimulation of LC might be mediated by the fibers passing through LC, while activation of LC neurons themselves would result in the depressor response.