Relationship of alpha-1- and alpha-2-adrenergic-binding sites to regions of the paraventricular nucleus of the hypothalamus containing corticotropin-releasing factor and vasopressin neurons.
To investigate catecholamine regulation of adrenocorticotropic hormone (ACTH) and vasopressin (VP) release, the relationship of alpha-adrenergic receptor-binding sites to corticotropin-releasing factor (CRF) and VP-containing cell populations within the paraventricular nucleus (PVN) of the hypothalamus was studied. Immunohistochemistry for CRF and neurophysin-vasopressin (NP-VP) was combined with receptor autoradiography. The adrenergic antagonist [3H]-prazosin was used to visualize alpha-1-binding sites and the agonist [3H]-p-aminoclonidine to visualize alpha-2-binding sites. To determine if changes in adrenergic binding accompanied experimentally induced increased activity of CRF- and VP-containing neurons, adrenalectomy was used as a stimulus for CRF release and dehydration as a stimulus for VP release. Quantitative assessment of autoradiograms revealed a greater density of alpha-1- and alpha-2-binding sites over the medial, parvocellular, CRF-containing region of PVN as compared to the lateral, magnocellular, NP-VP-containing region of the nucleus in all animal groups. Following 10 days of dehydration, the density of alpha-1- and alpha-2-binding sites associated with the CRF- and NP-VP-containing regions of PVN decreased. At 14 days postadrenalectomy the density of alpha-2-binding sites associated with CRF- and NP-VP-containing regions of the nucleus decreased, but the density of alpha-1-binding sites was unchanged. Results of this study support the hypothesis that epinephrine and/or norepinephrine regulate the release of ACTH and vasopressin via alpha-1- and alpha-2-adrenergic receptors associated with CRF- and VP-containing somata within the PVN.
D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000818:Animals; D001345:Autoradiography; D003000:Clonidine / Q000031:analogs & derivatives / Q000378:metabolism; D003346:Corticotropin-Releasing Hormone / Q000378:metabolism*; D007150:Immunohistochemistry; D008024:Ligands; D008297:Male; D009474:Neurons / Q000378:metabolism*; D010286:Paraventricular Hypothalamic Nucleus / Q000502:physiology*; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014667:Vasopressins / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D008024:Ligands; D011942:Receptors, Adrenergic, alpha; D014667:Vasopressins; C016986:apraclonidine; D003346:Corticotropin-Releasing Hormone; D003000:Clonidine; D011224:Prazosin