Units in the amygdala responding to activation of carotid baro- and chemoreceptors

Abstract

The distribution of units in the amygdala responding to selective activation of baro- and chemoreceptors was investigated in 12 cats under alpha-chloralose anesthesia. Changes in the firing frequency of spontaneously discharging units were monitored during baroreceptor activation (BA) (phenylephrine hydrochloride, 2 micrograms/kg iv) and chemoreceptor activation (CA) (sodium cyanide, 25 micrograms in 0.1 ml saline into the medial thyroid artery). CA altered the firing frequency of 23% (35/154) of the units; 37% (13/35) were excited, and 63% (22/35) were inhibited. BA altered the firing frequency of 16% (24/154) of the units; 71% (17/24) were excited, while 29% (7/24) were inhibited. The units responsive to CA were located primarily in the dorsomedial amygdala, while those responsive to BA were located primarily in the ventrolateral amygdala. The anatomic separation of units within the amygdala responding to activation of baroreceptors or chemoreceptors suggests that the specificity of function of different parts of the amygdala is related to the different kinds of inputs received by these components of the amygdala from cardiovascular receptors.