Cardiovascular responses to electrical stimulation of the septum in the rat.

CALARESU, FRANCO R., AND GORDON J. MOGENSON. Cardiovascular responses to electrical stimulation of the septum in the rat. Am. J. Physiol. 223(4): 777-782. 197 2 .-Cardiovascular responses to electrical stimulation of histologically verified sites in the septum were studied in 60 rats. In animals under a-chloralose anesthesia stimulation of the lateral septum (24 sites) elicited arterial hypotension, stimulation of the medial septum (19 sites) elicited arterial hypertension, and stimulation of an intermediate zone between the two areas (10 sites) elicited hypertension followed by hypotension. In contrast to these results, in animals under urethan anesthesia stimulation of the lateral septum (22 sites) elicited arterial hypertension and stimulation of the medial septum (10 sites) elicited arterial hypotension. In addition, on 10 occasions, stimulation of the lateral septum in animals under urethan elicited a hypertension accompanied by rhythmic oscillations of arterial pressure at a frequency of 24.6 =t 0.2/ min. In all animals stimulation of the septum did not elicit significant changes in heart rate but produced an increase in the frequency of respiration. The cardiovascular responses observed in animals under both anesthetics were not altered by the administration of tubocurarine. The optimal parameters of stimulation were found to be pulses of 2 msec duration at 80 Hz. It is concluded that the septum plays a very complex role in the central control of the cardiovascular system as indicated by the findings of two distinct and opposite responses in two different areas of the septum and by the reversal of the responses in animals under two different anesthetics.