The aims of the proposed study are to determine if peripheral and central osmoreceptors regulate the release of arginine vasotocin (AVT) and mesotocin (MT) from the fowl neurohypophysis and to begin a characterization of the afferent and efferent circuitries of the paraventricular nucleus (PVN). The effects of stimulating putative intracranial and cardiac osmoreceptors on the release of the hormones will be observed. Release of catecholamines at the PVN in response to peripheral stimuli will be related to the character and loci of adrenergic receptors in the anterior hypothalamus. Evoked changes in neurohypophysial and autonomic functions will be compared with release of AVT and MT at nerve terminals in the brainstem and the properties and loci of peptidergic receptors. Adrenergic and peptide receptors will be studied using radioligand assays on membranes and tissue sections. AVT and MT are measured by radioimmunoassays. The neural circuitry is studied using stereotaxic and intracranial microperfusion techniques. The results of the proposed study will increase our understanding of the physiology of AVT and MT in the fowl and the role the peptides play in regulating the endocrine and autonomic mechanisms that maintain homeostasis.
