title: The effect of stimulation of pre- and postsynaptic dopamine receptors on the endogenous inhibitor of cAMP-dependent protein kinase.
abstract: The effect of various doses of apomorphine on the activity of specific endogenous inhibitor of cAMP dependent protein kinase (type I inhibitor) was studied. Apomorphine produced biphasic changes in the type I inhibitor activity in rat striatum. Small doses (50-100 micrograms/kg) induced an increase while large doses (0.5-10 mg/kg) caused a dose dependent decrease of the type I inhibitor activity. The apomorphine induced increase in type I inhibitor activity was completely blocked by small, presynaptically active doses of haloperidol and chlorpromazine and by aminophylline. This suggests that small doses of apomorphine stimulate presynaptic dopamine D2-receptors. In contrast, the apomorphine induced decrease of the type I inhibitor activity was greatly potentiated by aminophylline and by presynaptically active doses of the neuroleptics, suggesting a postsynaptic site of action for large doses of apomorphine. Determination of the type I inhibitor activity is proposed as one of the biochemical tests allowing to recognize the site of action of drugs stimulating dopamine receptors.
mesh_terms: D000628:Aminophylline / Q000494:pharmacology; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002352:Carrier Proteins / Q000378:metabolism*; D002746:Chlorpromazine / Q000494:pharmacology; D004558:Electric Stimulation; D006220:Haloperidol / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D047428:Protein Kinase Inhibitors; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects*; D017981:Receptors, Neurotransmitter / Q000187:drug effects; D013997:Time Factors
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D011954:Receptors, Dopamine; D017981:Receptors, Neurotransmitter; C015482:protein kinase modulator; D000628:Aminophylline; D006220:Haloperidol; D001058:Apomorphine; D002746:Chlorpromazine