Heart rate response to sympathetic stimulation before and after sodium pentobarbital

Heart rate response to electrical stimulation of the right stellate ganglion of vagotomized cats was studied before and after the administration of sodium pentobarbital. The increase and decrease of heart rate with the initiation and cessation of sympathetic stimulation could be accurately described by separate exponential time functions. The time constants of rise and decline, the maximum steady-state heart rate, and the time between cessation of stimulation and initial decrease of heart rate (lag) were functions of the frequency and voltage of stimulation. The main effects of sodium pentobarbital were: 1) to prolong the rise of heart rate by 20-30 percent (P smaller than 0.0001),2) to prolong the decay of heart rate by 36-56 percent (P smaller than 0.005), and 3) to decrease the resting heart rate. The effects were observed 10 min after administration of the drug and lasted at least 4 h.