Alpha 1 adrenergic receptors in the porcine pituitary neurointermediate lobe: detection with [3H]ketanserin.
[3H]Ketanserin, a serotonin receptor antagonist, labelled high affinity, saturable sites in homogenates of porcine neurointermediate lobe tissue. Cinanserin, a potent and selective serotonin receptor antagonist, inhibited the specific binding of 5 X 10(-10)M [3H]ketanserin with a high affinity component representing 20% of the total binding. Prazosin, a potent and selective alpha 1 adrenergic antagonist, inhibited [3H]ketanserin binding with a high affinity component representing 60% of total binding. The prazosin-specific component was demonstrated to be distinct from the cinanserin-specific component. 10(-7)M cinanserin was co-incubated with [3H]ketanserin to eliminate the serotonergic component of the binding and allow pharmacological characterization of the remaining prazosin-specific component. The prazosin-specific binding of [3H]ketanserin binding closely resembled the results of experiments using [3H]prazosin to label alpha 1 receptors in neurointermediate lobe tissue homogenates. Ketanserin was found to be seven-fold more potent in inhibiting [3H]prazosin binding to alpha 1 adrenergic receptors in the neurointermediate lobe tissue than in brain tissue. This observation explains why low concentrations of [3H]ketanserin can selectively label serotonin receptors in the brain but will label both adrenergic and serotonin receptors in the neurointermediate lobe.
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002928:Cinanserin / Q000378:metabolism; D066298:In Vitro Techniques; D007650:Ketanserin; D007700:Kinetics; D010880:Piperidines / Q000378:metabolism*; D010902:Pituitary Gland / Q000378:metabolism*; D011224:Prazosin / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011985:Receptors, Serotonin / Q000378:metabolism; D013552:Swine
D010880:Piperidines; D011942:Receptors, Adrenergic, alpha; D011985:Receptors, Serotonin; D007650:Ketanserin; D002928:Cinanserin; D011224:Prazosin