Alterations of locus coeruleus 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 adrenocorticotropin (ACTH) and vasopressin responses. Increased vLC NA activity following the initial hemorrhage (InHem) persisted even after plasma hormone levels returned toward prestimulus values. Upon stimulus repetition, the peak increase in vLC NA activity was similar to that observed during InHem while the hormone responses were of greater magnitude (i.e. potentiated). Hence, it is suggested that the LC may exert a modulatory role in the hemodynamic control of hypothalamic-pituitary axis function.