Plasma corticosterone responses to electrical stimulation of the amygdaloid complex: cytoarchitectural specificity.

To pursue the possibility that subdivisions within the amygdaloid complex are differentially involved in adrenocortical function, plasma samples obtained prior to and following electrical stimulation of the amygdala of urethane (1.30 g/kg) anesthetized female rats were assessed for corticosterone concentration. Hippocampal EEG, ECG, heart rate, mean arterial pressure, and respiration routinely were monitored, and timed blood samples (0.2 ml) were obtained from a catheterized artery. Blood samples were taken 0.5 min prior to and at 5, 10, 15, and 30 min after initiation of stimulation. Whereas stimulation of the central and lateral nuclei produced a decrease (p less than 0.05) in plasma corticosterone, stimulation of the basomedial, medial and posterior corticomedial nuclei resulted in increased plasma corticosterone levels (p less than 0.05). In contrast, no change in corticosterone levels were observed following sham stimulation or stimulation of several nonamygdaloid sites. Collectively, these data support the hypothesis that subdivisions within the amygdaloid complex are differentially involved in adrenocortical function.