ergoline and 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonic-acid

Post-training administration of the N-methyl-D-aspartate (NMDA) receptors antagonist CPP, at doses of 0.5 and 1.0 mg/kg, impaired, in dose-dependent fashion, retention of the inhibitory avoidance response in C57BL/6J (C57) mice. Post-training subeffective doses of selective D1 and D2 dopamine receptor agonists, were able to antagonize the action of CPP, while subeffective doses of SCH 23390 and (-) sulpiride, respectively, D1- and D2-selective antagonists, enhanced the effects of the NMDA antagonist. Furthermore, subchronic blockade of dopamine receptor through a 10-day daily treatment with 4 mg/kg of haloperidol induced an adaptation of both the dopaminergic and the glutamatergic system. The possible upregulation of D2 receptors, in response to repeated injection with haloperidol is shown in the one-trial inhibitory avoidance by an increased response to the D2 agonist. In addition, our data show a potentiation of CPP effects after the same treatment. These results suggest a complex interaction between dopamine and glutamate in modulating one-trial inhibitory avoidance behavior in mice.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Avoidance Learning; Brain; Dopamine Agonists; Dose-Response Relationship, Drug; Electroshock; Ergolines; Haloperidol; Male; Mice; Mice, Inbred C57BL; Neural Inhibition; Piperazines; Quinpirole; Reaction Time; Receptors, Dopamine; Receptors, Dopamine D1; Receptors, Dopamine D2; Receptors, N-Methyl-D-Aspartate; Retention, Psychology

Competitive N-methyl-D-aspartate (NMDA) receptor antagonists, such as CPP and AP-7, dose-dependently enhanced the catalepsy induced by delta 9-tetrahydrocannabinol (THC; 5 mg/kg) in mice, but CPP failed to enhance haloperidol-induced catalepsy. The enhancing effect of CPP on THC-induced catalepsy was dose-dependently blocked by a muscarinic receptor antagonist, scopolamine, and by dopamine D1 and D2 receptor agonists such as apomorphine, SKF 38393 and quinpirole. The effect of CPP was quite opposite to that of the noncompetitive NMDA receptor antagonist MK-801. Therefore, the THC-induced catalepsy model may be useful for distinguishing between both classes of NMDA receptor antagonists.

Topics: 2-Amino-5-phosphonovalerate; 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Amantadine; Amino Acids; Animals; Anticonvulsants; Catalepsy; Dizocilpine Maleate; Dopamine Agonists; Dose-Response Relationship, Drug; Dronabinol; Drug Synergism; Ergolines; Haloperidol; Male; Mice; Mice, Inbred Strains; Motor Activity; Piperazines; Quinpirole; Receptors, N-Methyl-D-Aspartate; Scopolamine

The Flinders Sensitive Line of rats (FSL) has been selectively bred to have increased sensitivity to cholinergic drugs. Typically, these rats react with twice as great a hypothermic effect to muscarinic agonists such as oxotremorine, as do similarly bred Flinders Resistant Line rats (FRL). We compared the effects of three chemically different calcium channel inhibitors (diltiazem, nicardipine and verapamil) on the hypothermia induced in FRL and FSL rats by oxotremorine (0.2 mg kg-1 s.c.). Each drug was injected i.p. in a dose of 20 mumol kg-1 30 min before oxotremorine. Methylatropine (2 mg kg-1 s.c.) was administered 15 min before oxotremorine to block the peripheral effects of the agonist. The hypothermic effect of oxotremorine in FSL rats was antagonized by nicardipine and diltiazem. In contrast, verapamil failed to influence the hypothermic response in FSL rats. Verapamil significantly (P less than 0.05) augmented oxotremorine hypothermia in FRL rats. Diltiazem and nicardipine were without effect on oxotremorine-induced hypothermia in FRL rats. There were no significant changes in temperature in separate groups of FRL and FSL rats treated with calcium channel inhibitors alone.

Topics: Animals; Apomorphine; Atropine Derivatives; Body Temperature; Calcium Channel Blockers; Dopamine Agents; Ergolines; Male; Oxotremorine; Parasympathetic Nervous System; Piperazines; Quinpirole; Rats; Rats, Inbred Strains; Receptors, N-Methyl-D-Aspartate

Administration of the 5-HT1C/5-HT2 receptor agonist 1-(2,5-dimethoxy-4- iodophenyl)-2-aminopropane (DOI, 0.125-2.0 mg/kg i.v.) triggered dose-dependent increases in plasma glucose; plasma insulin levels remained unchanged. Pretreatment with the 5-HT1C/5-HT2 receptor antagonists LY 53857, ritanserin, or the mixed 5-HT2/alpha 1-adrenoceptor antagonist ketanserin either diminished or prevented the hyperglycemic effect of DOI (0.5 mg/kg). Administration of the mixed 5-HT1C receptor agonists/5-HT2 receptor antagonists 1-(3-chlorophenyl)-piperazine (mCPP) or 1-(3-trifluoromethyl)phenyl)piperazine level (TFMPP) did not affect plasma glucose levels. However, pretreatment with mCPP or TFMPP decreased DOI-induced hyperglycemia in a dose-dependent manner. The alpha 2-adrenoceptor antagonist idazoxan and the ganglionic blocker hexamethonium both decreased DOI-induced hyperglycemia, Whilst the alpha 1-adrenoceptor antagonist prazosin amplified the rise in plasma glucose elicited by DOI. The peripherally acting 5-HT1C/5-HT2 receptor agonist alpha-methyl-5-HT (0.5-1.0 mg/kg i.v.) triggered a rise in plasma glucose levels that was associated with an increase in plasma insulin levels. Pretreatment with LY 53857 diminished alpha-methyl-5-HT-induced hyperglycemia. These data indicate that 5-HT2 receptors, but not 5-HT1C receptors, and catecholaminergic systems, mediate DOI-induced hyperglycemia. Moreover, it is suggested that the inhibition of insulin release by DOI is centrally mediated, and that activation of peripheral 5-HT2 receptors may affect glycemia.

Topics: Amphetamines; Animals; Blood Glucose; Catecholamines; Ergolines; Hyperglycemia; Insulin; Male; Piperazines; Piperidines; Rats; Rats, Inbred Strains; Receptors, Serotonin; Ritanserin; Serotonin