Baroreceptor reflex during arousal induced by electrical stimulation of the amygdala or by natural stimuli

Baroreceptor control of heart rate was studied in 14 unanaesthetized cats during rest and arousal induced by either electrical stimulation of the central nucleus of the amygdala or by natural stimuli. The baroreceptor reflex was elicited by i.v. injections of angiotensin II and the sensitivity of the vagal component of the reflex expressed as the regression coefficient of the relationship between the systolic blood pressures of successive arterial pulses and their pulse intervals. Baroreceptor reflex sensitivity was reduced by all types of arousing procedure studied; an effect assumed to be a part of integrated cardiovascular adjustments accompanying arousal. Further studies in slightly anaesthetized cats were performed in order to investigate the time-course of such changes in reflex sensitivity. Th inhibition of the vagal component of the reflex did not last for the entire period of the electrically elicited arousal and it is suggested, therefore, that this might reflect the activation of mechanisms which limit orienting behaviour. Overall, these results indicate that the central nucleus of the amygdala may be involved in a transient integration of cardiovascular and behavioural responses during arousal.