EAA RECEPTORS IN THE DORSOMEDIAL HYPOTHALAMIC AREA MEDIATE THE CARDIOVASCULAR-RESPONSE TO ACTIVATION OF THE AMYGDALA

The role of excitatory amino acid (EAA) receptors in the dorsomedial h ypothalamus (DMH) in mediating the cardiovascular response to activati on of the basolateral amygdala (BLA) was examined using conscious rats . Microinjection of the nonselective EAA. receptor antagonist kynureni c acid (0.1-10 nmol) into the DMH blocked or reversed the increases in heart rate and arterial pressure resulting from injection of the GABA (A) receptor antagonists bicuculline methiodide (BMI; 100 pmol) and pi crotoxin (100 pmol) into the BLA. Similar injections of kynurenic acid at sites lateral or dorsal to the DMH or injection of the inactive an alog xanthurenic acid into the DMH were less effective in blocking the cardiovascular changes resulting from intraamygdalar injection of BMI . Hypothalamic injection of the NMDA receptor antagonist 3-(2-carboxyp iperazin-4-yl)-propyl-1-phosphonic acid (10 pmol) or the -alpha-amino- 3-hydroxy-5-methylisoxazole-propionic acid receptor antagonist -nitro- 2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide amide (50 pmol) at doses s hown to be selective for their respective EAA receptor subtypes attenu ated the cardiovascular changes associated with intra-amygdalar inject ion of BMI. Therefore, EAA receptors in the area of the DMH appear to be involved in mediating the cardiovascular changes resulting from act ivation of the amygdala.