Responses of adrenocorticotropin and vasopressin to hemorrhage after lesions of the caudal ventrolateral medulla in rats.

Hormonal responses to hemorrhage were examined in urethane-anesthetized rats 48 h after electrolytic lesions of the caudal ventrolateral medulla. Bilateral A1-lesions (A1X) inhibited the response of plasma adrenocorticotropin relative either to other lesions (XX) or to sham lesions. A1X inhibited the response of plasma vasopressin relative to XX but not to sham lesions. A1X and XX destroyed similar areas that were dorsal or caudal to A1. No lesion blocked either response completely. A hemodynamic pathway controlling the release of both hormones may pass through A1. However, other pathways may bypass this area.