ALTERATIONS OF LOCUS-CERULEUS NORADRENERGIC ACTIVITY IN RELATION TO PITUITARY SECRETION AFTER HEMORRHAGE IN CATS

Noradrenergic (NA) activity in the cat ventral locus coeruleus (vLC). measured either by voltammetry or by push pull perfusion. increased in response to hemorrhage. This stimulus also elicited plasma adrenocort icotropin (ACTH) and vasopressin responses. Increased vLC NA activity following the initial hemorrhage (InHem) persisted even after plasma h ormone levels returned toward prestimulus values. Upon stimulus repeti tion. the peak increase in vLC NA activity was similar to that observe d during InHem while the hormone responses were of greater magnitude ( i.e. potentiated). Hence, it is suggested that the LC may exert a modu latory role in the hemodynamic control of hypothalamic-pituitary axis function.