Effects of Sodium Pentobarbital on Electrical and Reflex Activation of the Cardiovascular System.

• The effects of barbiturates on the cardiovascular system have been reported by many investigators. These effects include reduction of vagal inhibition of the heart rate,direct myocardial depression,and depression of pressor responses to sciatic nerve stimulation." Bouckaert and Heymans reported that the carotid sinus reflex in dogs is depressed by barbiturates. Several investigators have concluded that these anesthetic agents have a significant effect on central neural mediation of cardiovascular reflexes. Masserman showed that sympathetic responses to faradic stimulation of the hypothalamus in the cat are markedly decreased by sodium Amytal in doses of 20 to 50 mg/kg. He also demonstrated a decrease in blood pressure when small amounts of this drug were injected directly into the hypothalamus. Similar results were reported by Dikshit, who also demonstrated depression of chloroform-induced arrhythmias by barbiturates. Redgate and Gellhorn n reported that injection of sodium thiopental into the posterior hypothalamus of cats produced a fall in blood pressure and heart rate, with recovery to control levels occurring 25 to 30 minutes later. Reduction of pressor responses and reversal to depressor responses during electrical stimulation of the brain stem was shown recently by Gutman et al. Peiss suggested a hypothalamic site of action for the depressant effects of pentobarbital on cardiovascular responses in the cat. Since it is known that large doses of