Eight Annual Conference on Shock

Central serotonergic neurons impinging upon sympathetic' preganglionic neurons have been implicated in the regulation of blood pressure. Using anesthetized cats we recorded the mean arterial blood pressure and splanchnic nerve activity before, during, and after hemorrhage. Ten cats were untreated, while five cats were given parachlorophenylalanine (p-CPA, 300 mg.kg- 1, i.p., 40 to 48 hours prior to hemorrhage), to deplete serotonin. All cats were hemorrhaged to 40 + or - 2 mm Hg for one hour using a pressure-activated, servo-controlled pump. Thereafter, pressure regulation was stopped. After two hours of oligemia, the shed blood was reinfused, and the cats monitored for an additional two hours.