SKF 81297 hydrobromide

Pharmacological characterization of the discriminative stimulus properties of the dopamine D1 agonist, SKF 81297.[Pubmed:11224180]

Behav Pharmacol. 1993 Apr;4(2):135-146.

A range of selective dopamine D1 and D2 receptor agonists and antagonists was used to characterize to the discriminative stimuli produced by d-amphetamine (0.5mg/kg) and the D1 agonists SKF 81297 (0.1mg/kg). In rats trained to discriminate d-amphetamine (0.5mg/kg) from saline, d-amphetamine produced a dose-related increase in per cent drug lever responding, and SKF 81297 did not show any d-amphetamine-like discriminative stimulus effects; neither did SKF 81297 potentiate nor antagonize the d-amphetamine discriminative stimulus. In rats trained to discriminate SKF 81297 (0.1mg/kg) from saline, SKF 81297 produced a dose-related increase in per cent drug lever responding, and SKF 38393 and SKF 83565 elicited full SKF 81297-like effects despite the fact that these compounds have widely differing efficacies for stimulating adenylate cyclase. SKF 81297 had a 25-fold greater potency than SKF 38393 in this assay. The D2 agonists, PHNO and ropinirole, did not display any SKF 81297-like discriminative stimulus effects. The SKF 81297 discriminative stimulus was completely blocked by the D1 antagonist SCH 23390 but was not blocked by the D2 antagonist BRL 34778.

The effects of dopamine D1 and D2 receptor agonists and antagonists in monkeys withdrawn from long-term neuroleptic treatment.[Pubmed:1980891]

Eur J Pharmacol. 1990 Sep 4;186(1):49-59.

The effects of dopamine D1 and D2 receptor agonists and antagonists were studied in eight Cebus apella monkeys previously treated with haloperidol for two years. SKF 81297 (specific D1 receptor agonist) induced oral hyperkinesia of variable intensity (P less than 0.01): some of the monkeys developed extreme lip smacking, tonque protrusions and licking movements while others developed only slight lip movements. A combined treatment of SKF 81297 with LY 171555 (full D2 receptor agonist) or SCH 23390 (D1 receptor antagonist) inhibited the oral hyperkinesia induced by SKF 81297 (P less than 0.01, P less than 0.02, respectively). Raclopride (D2 receptor antagonist) did not statistically change oral hyperkinesia (P less than 0.2), although five monkeys showed increased oral movements; most of these monkeys had pre-existing hyperkinesia. Treatment with SCH 23390 or raclopride resulted in an identical dystonic/cataleptic syndrome. SKF 81297 inhibited the dystonia induced by SCH 23390, while it did not significantly affect raclopride dystonia. The investigation indicates that oral dyskinesia may be related to an imbalance in D1 receptor and D2 receptor stimulation in favor of D1 receptors. The question now is whether D1 receptor antagonists, which may have antipsychotic potential, will produce tardive dyskinesia after long-term use.

Relative dopamine D1 and D2 receptor affinity and efficacy determine whether dopamine agonists induce hyperactivity or oral stereotypy in rats.[Pubmed:3259694]

Pharmacol Toxicol. 1988 Mar;62(3):121-30.

The effects of a range of dopamine (DA) agonists on stereotyped behaviour in rats were analysed and compared both with the affinity of the compounds for D1 and D2 receptor binding sites in vitro and their ability to stimulate the adenylate cyclase activity in rat striatal homogenates. Full and partial agonists at the D1 receptor coupled to adenylate cyclase do not induce sterotypies when given alone, whereas full D2 agonists (e.g. quinpirole) induce hyperactivity but not oral sterotypies. Partial D2 agonists (e.g. (-)-3-PPP) only induce sedation. Mixed D1/D2 agonists (e.g. apomorphine) induce both hyperactivity and oral stereotypies. Maximum stereotypies were induced by combination of SK & F 38393 and a series of D2 agonists, including full agonists and the partial D2 agonist B-HT 920, whereas partial agonists with low intrinsic activity (e.g. (-)-3-PPP, EMD 23448) did not induce stereotypies when given together with SK & F 38393. However, these partial agonists reduced the maximum effect of apomorphine, whereas the full agonists (e.g. quinpirole, (-)-NPA) and B-HT 920 had no apomorphine antagonistic activity. The mixed D1/D2 agonists apomorphine and N,N-dipropyl-5,6-ADTN were only weakly influenced by SK & F 38393, or not at all. D1 agonists with central effects, including SK & F 38393, SK & F 81297 (with relatively high efficacies), and the partial agonist SK & F 75670 with low efficacy, changed the hyperactivity induced by quinpirole into maximum oral stereotypy, whereas the peripheral D1 agonist fenoldopam had no such effect. Inhibition of DA and NA synthesis with alpha-methyl-p-tyrosine depleted striatal DA levels by 72 per cent and antagonized the hyperactivity induced by the D2 agonists quinpirole and (-)-NPA, but not that of apomorphine. Combination of SK & F 38393 and quinpirole induced maximum stereotypy in DA-depleted animals. These results suggest that D1 receptor tonus is a necessary prerequisite for the expression of a DA agonist's effect. The hyperactivity induced by full D2 agonists appears to be mediated by D1 tonus provided by endogenous DA activity, but stronger D1 stimulation is necessary to induce oral stereotypy. A high degree of D1 receptor activation increases the ability of partial D2 agonists to induce hyperactivity or oral stereotypies since treatment with both SK & F 38393 and B-HT 920 had marked effects while B-HT 920 was ineffective.(ABSTRACT TRUNCATED AT 400 WORDS)