Role of Ventrolateral Medulla Catecholamine Cells in Hypothalam Neuroendocrine Cell Responses to Systemic Hypoxia ic

Systemic hypoxia stimulates the release of vasopressin (VP) and adrenocorticotropin hormone (ACTH). To examine the involvement of catecholamine cell groups of the ven-trolateral medulla (VLM) in the neuroendocrine responses, we have used the c-fos activity mapping technique to com-pare the effects of hypoxia on VLM catecholamine cells to those on neurosecretory VP and putative corticotropin re-leasing factor (CRF) containing cells. A limited degree of catecholamine cell activation was evident at predominantly mid-VLM levels at 12 % oxygen in the inspired air. Further reduction in inpsirate oxygen levels enhanced recruitment of caudally located VLM catecholamine cells considered to form part of the Al noradrenergic cell group. Threshold for activation of VP and putative CRF cells occurred at the 10% oxygen level. Unexpectedly, this stimulus also activate