An improved radioimmunoassay for alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat: serum and pituitary alpha-MSH levels after drugs which modify catecholaminergic neurotransmission.
A modification of our previous radioimmunoassay (RIA) for alpha-melanocyte-stimulating hormone (alpha-MSH) is described that permits the measurement of circulating levels in the rat without the need for an extraction procedure. Using this method, serum and neurointermediate lobe (NIL) immunoreactive alpha-MSH levels were measured in rats after administration of haloperidol, 2-bromo alpha-ergocryptine (CB 154), and alpha-methyl-p-tyrosine (alpha-MPT). Haloperidol caused a rapid increase, alpha-MPT a slow increase, and CB 154 a rapid decrease in serum alpha-MSH. At the time intervals studied none of the drugs had any significant effect on NIL alpha-MSH content. It was concluded from the results of the above drug treatments that modulation of dopaminergic neurotransmission both pre- and postsynaptically produces changes in serum immunoreactive alpha-MSH levels. This supports the suggestion that circulating alpha-MSH in the rat is under an inhibitory control by a catecholaminergic system.
D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D002395:Catecholamines / Q000502:physiology; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D009074:Melanocyte-Stimulating Hormones / Q000032:analysis* / Q000097:blood / Q000378:metabolism; D008781:Methyltyrosines / Q000494:pharmacology; D010902:Pituitary Gland / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects*
D002395:Catecholamines; D008781:Methyltyrosines; D001971:Bromocriptine; D009074:Melanocyte-Stimulating Hormones; D006220:Haloperidol