Drugs online research references
Eur J Pharmacol. 1978 Jan 15;47(2):191-200.
Effects of baclofen on dopamine metabolism and interaction with neuroleptic effects.
Waldmeier PC, Maitre L.
Baclofen increased striatal levels of dopamine (DA), homovanillic (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) dose-dependently above 10 mg/kg i.p. The effect on the DA metabolites was shown to be caused only by the (-)-isomer. The HVA increase after 20 mg/kg i.p. was not antagonized by either scopolamine or picrotoxin. Repeated treatment produced a smaller increase in HVA than a single administration. Baclofen reduced both the disappearance of DA after alpha-methyl-p-tyrosine and the acceleration of the DA disappearance caused by neuroleptics in corpus striatum and in the mesolimbic area. The neuroleptic-induced increases in HVA and DOPAC and in DOPA accumulation after central decarboxylase inhibition were also reduced. Picrotoxin could not antagonize these effects of baclofen which therefore cannot be regarded as being garbergic. Baclofen effects on DA metabolism are similar to those reported for gamma-hydroxybutyric acid and are probably a consequence of inhibition of firing of DA neurons.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=23298&dopt=Abstract
Eur J Pharmacol. 1988 Apr 13;148(3):389-95.
SCH 23390--a selective dopamine D-1 receptor antagonist with putative 5-HT1 receptor agonistic activity.
Skarsfeldt T, Larsen JJ.
Department of Pharmacology and Toxicology, H. LUNDBECK A/S, Copenhagen-Valby, Denmark.
The selective dopamine D-1 receptor antagonist SCH 23390 has been tested in vitro in the rat fundus model and in vivo in the electrically stimulated flexor reflex model. In the fundus model, SCH 23390 showed a potent agonistic activity compared to that of different 5-HT receptor agonists. Pindolol, 1-propranolol and pirenperone showed no or only weak inhibition of the SCH 23390-induced contractions in the fundus strip whereas methysergide was a potent inhibitor. The 5-HT3 receptor antagonist ICS 205-930 did not induce an inhibitory effect. In the electrically stimulated flexor reflex model in pithed rats, SCH 23390 induced a marked increase of the reflex. This increase was slightly inhibited by a mixed dopamine (DA) D-1/D-2 antagonist cis(Z)-flupentixol and by a specific DA D-2 antagonist YM 09151-2. Different reference antagonists: bicuculline (GABAergic), propranolol (beta-adrenergic), scopolamine (muscarinic), yohimbine (alpha 2-adrenergic), prazosin (alpha 1-adrenergic) were all without an antagonist effect on the SCH 23390-induced increase of the flexor reflex. Ketanserin, a selective 5-HT2 receptor antagonist, showed a weak and short-lasting inhibition of the SCH 23390 effect in high doses, whereas ritanserin showed only 35% inhibition of the SCH 23390-induced flexor reflex at a dose of 1.3 mumol/kg i.v. The mixed 5-HT1/5-HT2 antagonists methiothepin and metergoline showed a marked inhibitory effect at 2.6 mumol/kg i.v. and 3.1 mumol/kg i.v., respectively (1.3 mg/kg i.v.). These findings suggest that SCH 23390 might possess 5-HT1 receptor agonist activity.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2968272&dopt=Abstract
Eur J Pharmacol. 1981 Jun 10;72(1):69-75.
Differential effects of dopamine agonists in mature and immature rats.
McDevitt JT, Setler PE.
It has been suggested that because of a relatively slow maturation of the central cholinergic system, that the neonatal rat (i.e. less than 2 weeks old) may be used as an in vivo model, with minimal cholinergic influence, for studying the effects of dopaminergic compounds. d-Amphetamine, 1-DOPA, and SK and F 38393-A produce a syndrome in neonatal rat similar to the stereotyped behavior characteristically produced by dopamine agonists. This neonatal syndrome includes increased motor activity and sniffing plus licking and/or biting. Apomorphine and bromocryptine do not produce this behavior in neonatal rats. The potencies of d-amphetamine, 1-DOPA, and SK and F 38393-A in producing this syndrome decrease with the age of the rat. Increases in motor activity, or sniffing plus licking and/or biting by d-amphetamine 1-DOPA, or SK and F 38393-A, in thirty and/or sixty day old rats are significantly enhanced by scopolamine pretreatment. Apomorphine- or bromocryptine-induced stereotyped behavior in thirty and sixty day old rats is not affected by scopolamine. These data suggest that the effects of certain dopaminergic agonists, which produce the neonatal syndrome, are modulated in the adult rat by cholinergic activity. The ineffectiveness of apomorphine in the neonate, however, suggest that the neonatal syndrome may not be related exclusively to dopamine, or that the dopaminergic system involved with this behavior is not sensitive to apomorphine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6973482&dopt=Abstract
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