NeuroendocrinologyNTS catecholamine cell recruitment by hemorrhage and hypoxiaBuller, K M.1,2; Smith, D W.1; Day, T A.1Author Information 1Department of Physiology and Pharmacology, University of Queensland, Brisbane, Queensland 4072, Australia 2Corresponding Author: K. M. Buller ACKNOWLEDGEMENTS: This work was supported by project grants to T.A.D. from the National Health and Medical Research Council of Australia and the National Heart Foundation of Australia. We thank Mary McKenna and Melanie Voigt for technical assistance and Dr. D. Pow of the Vision, Touch and Hearing Research Centre for the provision of VP and OT antiserum. Received 8 September 1999; accepted 6 October 1999 NeuroReport: December 16th, 1999 - Volume 10 - Issue 18 - p 3853-3856 Buy SDC Abstract IMMUNOLABELLING for Fos and tyrosine hydroxylase was used to determine the patterns of activation of nucleus tractus solitarius catecholamine cells in response to graded levels of hemorrhage (0, 4, 8, 12 and 16 ml/kg) and systemic hypoxia (21, 14, 12, 10 and 8% O2) in conscious rats. Both stimuli elicited graded catecholamine cell recruitment with thresholds of 8 ml/kg and 12% O2. The majority of responsive neurons were A2 noradrenergic rather than C2 adrenergic cells. After hemorrhage most Fos-positive catecholamine cells were found below obex whereas most hypoxia-responsive cells were rostral to obex. These distinctive patterns of catecholamine cell recruitment may explain the differences in neuroendocrine responses to these stimuli. © 1999 Lippincott Williams & Wilkins, Inc.