Correlation of dopamine and opiate binding with adenylate cyclase in rat striatum
The neuroleptic properties of opiate drugs in striatum are well-recognized, but the mechanisms underlying these properties are not known (Lal, 1975). Recently it was reported that opiates inhibit the dopamine (DA)-activated adenylate cyclase of monkey amygdala (Walczak et al., 1979) and rat striatal membranes (Neff et al., 1981). However, no interaction between DA and opiate binding has been observed under standard binding assay conditions (Burt et al., 1976; Snyder et al., 1975). In this study, micromolar, rather than nanomolar, DA binding was measured under assay conditions in which DA activates adenylate cyclase and opiates inhibit the activation. There is a strong correlation between the ability of opiates to block micromolar DA binding and to block activated adenylate cyclase. GTP and dithiothreitol (DTT) appear to be required for these effects. Thus, at least some of the neuroleptic effects of opiates can be attributed to blockade of the D1 receptor as defined by Kebabian and Calne (1979) in striatum.
KeywordsAdenylate Cyclase Cyclase Activity Sucrose Gradient Adenylate Cyclase Activity Opiate Receptor
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