Characterization and pharmacological studies of an octopamine-sensitive adenylate cyclase from nerve cord of Locusta migratoria.

An octopamine-sensitive adenylate cyclase that is insensitive to stimulation by dopamine (DA) and 5-hydroxytryptamine (5-HT), was studied in a homogenized nerve cord preparation of the migratory locust, Locusta migratoria. The enzyme complex is similar to catecholamine-sensitive cyclases from mammals with respect to pH-optimum, requirement for Mg++ and GTP, and sensitivity to forskolin. The octopamine-mediated elevation of adenylate cyclase activity is antagonized by a variety of drugs with the following order of potency: mianserin greater than phentolamine greater than promethazine greater than gramine greater than cyproheptadine greater than cis-flupenthixol greater than chlorpromazine greater than metoclopramide.