Binding of [3H]phencyclidine to membranes from housefly thoracic muscles

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Abstract
The binding of [3H]phencyclidine ([3H]PCP) to a preparation of housefly thoracic muscle membranes was studied. Specific [3H]PCP binding saturated with both time and at concentrations of the radiolabeled ligand greater than 20 nM. One binding site with a KD of 10.7 nM and a Bmax of 3.9 pmol/mg protein was observed. Specific [3H]PCP binding was also readily reversible with a half‐time of dissociation (t1/2) of 13.8 min and varied proportionately with tissue concentration. Of the drugs tested, specific [3H]PCP binding was inhibited by PCP analogs, antipsychotics, antidepressants, Ca2+ channel antagonists, and K+ channel blockers. [3H]PCP binding was unaffected by addition of carbamylcholine or L‐glutamate in absence or presence of ATP, GTP, cAMP, or cGMP. Though the identity of the [3H]PCP binding protein in housefly muscle membranes is still unclear, it is more likely to be an ionic channel such as K+ or Ca2+ channels than a neurotransmitter receptor.