Postsynaptic dopamine (DA) receptor stimulator properties of the putative DA autoreceptor-selective agonist B-HT 920 uncovered by co-treatment with the D-1 agonist SK&F 38393.
Postsynaptic dopaminergic behavioural effects of D-2 agonists can be promoted by concomitant D-1 receptor activation. The present experiment explored whether such effects could be elicited by the putative autoreceptor-selective D-2 agonist B-HT 920, when combined with the D-1 agonist SK&F 38393. Except for occasional jerks induced by B-HT 920, neither agonist caused significant dopaminergic stimulation when given separately, whereas combined treatment with SK&F 38393 and B-HT 920 induced clear-cut motor activation--particularly focused stereotyped licking and sniffing--in reserpine/AMT-pretreated rats. Both the D-1 antagonist SCH 23390 and the D-2 antagonist spiperone abolished these effects, while the SK&F/B-HT-induced stimulation was not significantly affected by the alpha 2-blocker idazoxan. It appears that classical postsynaptic DA receptor-stimulatory properties of B-HT 920 can indeed be demonstrated, provided that sufficient D-1 receptor tone prevails.
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D001067:Appetite Depressants / Q000494:pharmacology*; D001381:Azepines / Q000494:pharmacology*; D001552:Benzazepines / Q000494:pharmacology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D011954:Receptors, Dopamine / Q000187:drug effects*; D013134:Spiperone / Q000494:pharmacology; D013239:Stereotyped Behavior / Q000187:drug effects; D013569:Synapses / Q000187:drug effects*
D000316:Adrenergic alpha-Agonists; D001067:Appetite Depressants; D001381:Azepines; D001552:Benzazepines; D011954:Receptors, Dopamine; D013134:Spiperone; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; C024763:talipexole