title: Initial detection of [3H]prazosin-labeled alpha 1-receptors in the porcine pituitary neurointermediate lobe.
abstract: [3H]Prazosin binding to alpha 1-adrenergic receptors was investigated in homogenates of tissue from the porcine pituitary neurointermediate lobe. Potent alpha 1-adrenergic antagonists such as prazosin, WB-4101, and phentolamine displayed high potency in competing for [3H]prazosin specific binding in pituitary tissue. Epinephrine and norepinephrine were the only neurotransmitters which displayed high potency in competing for [3H]prazosin binding sites. There was a strong correlation in the pharmacological properties of the alpha 1 sites in pituitary tissue and the alpha 1 sites detected by [3H]prazosin in rat brain tissue. Alpha-adrenergic agonists demonstrated significantly higher potency for the alpha 1-receptor sites in pituitary tissue than in brain tissue preparations. The antagonist ketanserin demonstrated significantly higher potency at alpha 1 sites in pituitary tissue than in brain tissue. This latter observation has important implications for investigators attempting to use [3H]ketanserin as a selective serotonin receptor ligand in pituitary tissue. The results of this study represent the first demonstration of alpha 1-receptors in mammalian neurointermediate lobe tissue.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000378:metabolism; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D005260:Female; D066298:In Vitro Techniques; D010902:Pituitary Gland / Q000378:metabolism*; D011224:Prazosin; D011799:Quinazolines; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000032:analysis*; D013552:Swine
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; D011942:Receptors, Adrenergic, alpha; D011224:Prazosin