The motor activity of reserpine-treated mice was used to study effects of B-HT 958 (2-amino-6-(p-chlorobenzyl)-4H-5,6,7,8-tetrahydrothiazolo-[5,4-d]- azepine) on postsynaptic dopamine and noradrenaline receptors. The motor activity was only slightly stimulated by B-HT 958 or by the D1- receptor agonist SKF 38393 but it was markedly increased by the two drugs given in combination. The effect of B-HT 958 peaked earlier following low rather than high doses. The enhanced motor activity was inhibited by the D2- receptor antagonist sulpiride or the D1- receptor antagonist SCH 23390, indicating that it was caused by stimulation of both receptor types. The results suggest that B-HT 958 stimulates postsynaptic D2- receptors in addition to D2- autoreceptors and that its blockade of postsynaptic alpha 2-adrenoceptors is of no importance for the motor activity.
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Effect on rat feeding behavior of two selective D2 dopamine agonists.
Physiol Behav
November 1994
Department of Biomedical Sciences, University of Modena, Italy.
B-HT 958 and SND 919, two selective agonists at D2 dopamine receptors, were examined for their influence on the feeding behavior of fasted rats. When food intake was determined in the rat's individual home cage, it was found to be reduced by both drugs at low sedative doses during the first hour after treatment and by SND 919 at the highest dose (which also elicits stereotypy) only 24 h later. However, SND 919 and B-HT 958 had no significant effect on feeding evaluated according to the X-maze and tube feeding tests.
View Article and Find Full Text PDFBehavioural effects induced in rats and chicks by D2 dopamine agonists.
Physiol Behav
October 1993
Institute of Pharmacology, University of Modena, Italy.
In a first series of experiments, different selective dopamine D2 receptor agonists (B-HT 920, B-HT 958, SND 919, CQ 32-084, CQP 201-403, and lisuride) and the D1/D2 agonist apomorphine were IP injected into adult male rats. At low doses, they elicited repeated episodes of penile erection and stretching-yawning: at all doses tested, B-HT 920, B-HT 958, and CQ 32-084 also induced hypomotility, a sign that, in the case of high doses of SND 919, CQP 201-403, lisuride, and apomorphine, was replaced by stereotyped behaviour. In a second series of experiments, the same D2 agonists and the mixed D1/D2 agonist apomorphine were IP injected at the same doses into chicks.
View Article and Find Full Text PDFEffect of the D2-autoreceptor agonist B-HT 958 on both spontaneous and ACTH-induced stretching, yawning and grooming in the rat.
Life Sci
April 1992
Institute of Pharmacology, University of Modena, Italy.
The D2 autoreceptor agonist B-HT 958, intraperitoneally injected into Wistar male rats in a novel environment, significantly increased stretching and yawning (SY) while inhibiting grooming. Pretreatment with the D2 antagonist sulpiride reversed these effects, antagonizing SY and restoring grooming. Similarly, when B-HT 958 was administered to rats in their home cages, it elicited SY and abolished grooming; moreover, when administered before the i.
View Article and Find Full Text PDFStimulation of postsynaptic D2- dopamine receptors by B-HT 958 is revealed by co-treatment with the D1- receptor agonist SKF 38393.
J Pharm Pharmacol
July 1989
Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden.
The motor activity of reserpine-treated mice was used to study effects of B-HT 958 (2-amino-6-(p-chlorobenzyl)-4H-5,6,7,8-tetrahydrothiazolo-[5,4-d]- azepine) on postsynaptic dopamine and noradrenaline receptors. The motor activity was only slightly stimulated by B-HT 958 or by the D1- receptor agonist SKF 38393 but it was markedly increased by the two drugs given in combination. The effect of B-HT 958 peaked earlier following low rather than high doses.
View Article and Find Full Text PDFB-HT 920 antagonizes rat neophobia in the X-maze test: a comparative study with other drugs active on adrenergic and dopaminergic receptors.
Arch Int Pharmacodyn Ther
September 1989
Institute of Pharmacology, University of Modena, Italy.
Since there is compelling evidence to suggest a significant participation of central noradrenergic (NA) and dopaminergic (DA) pathways in the modulation of anxiety disorders, the possible tranquillizing effect of B-HT 920, considered to be a selective agonist of central DA autoreceptors at low doses, but also a stimulant of central alpha 2-receptors at high doses, was investigated by means of the X-maze test. For comparison, other drugs active on alpha-adrenoceptors and DA receptor subtypes were similarly tested. B-HT 920 at high doses (1 and 2 mg/kg) significantly antagonized the animals' spontaneous avoidance of open spaces (a sign indicative of anxiety), despite the reported sedative effects of the drug; it should be pointed out, however, that the latter were observable in our tests only at 1 mg/kg, a more pronounced sedation was the sole effect of a low dose (100 micrograms/kg) of B-HT 920.
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