ergoline and Hypothermia

Clozapine (7.5-30.0 mumol kg-1 s.c.) produced a decrease in core temperature in the rat. The temperature decrease caused by clozapine (7.5 mumol kg-1 s.c.) was fully antagonized by the selective dopamine D1 receptor antagonist SCH 23390 (0.3 mumol kg-1) s.c.) and a partial antagonism was obtained by the selective dopamine D2 receptor antagonist raclopride (1.6 mumol kg-1 s.c.). On the other hand, the hypothermia was not antagonized by alpha-adrenoceptor antagonists (idazoxan and prazosin), 5-HT receptor antagonists ((-)-pindolol and ritanserin) or by the muscarinic M1 receptor antagonist scopolamine. The hyperthermia produced by the 5-HT1C/2 receptor agonist DOI (0.75 mumol kg-1) was blocked by clozapine (3.0 mumol kg-1 s.c.). Clozapine did not antagonize hypothermia produced by selective dopamine D1 and D2 receptor agonists (A 68930 and quinpirole), the alpha 2-adrenoceptor agonist clonidine, the 5-HT1A receptor agonist 8-OH-DPAT (8-hydroxy-2-(di-n-propylamino)tetralin) or the muscarinic M1 receptor agonist oxotremorine. The present results suggest that clozapine may be a partial agonist at brain dopamine D1 receptors.

Topics: Amphetamines; Animals; Benzazepines; Body Temperature; Body Temperature Regulation; Chromans; Clonidine; Clozapine; Dopamine Agents; Dopamine D2 Receptor Antagonists; Ergolines; Hypothermia; Injections, Subcutaneous; Male; Oxotremorine; Quinpirole; Raclopride; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D1; Salicylamides; Serotonin Antagonists

Remoxipride and its active metabolites, the phenolic compounds FLA797(-) and FLA908(-) and the catecholic NCQ436(-) and haloperidol, were examined for their ability to block hypothermia in the rat induced by dopamine (DA) D2 receptor stimulation. In addition, plasma levels of remoxipride and its active metabolites were measured using HPLC methods. Remoxipride (1 mumol/kg), given 30 or 15 min prior to, or 5 and 15 min after, the DA agonists, blocked the hypothermia induced by the DA D2 receptor agonists quinpirole (0.25 mg/kg s.c.) and pergolide (0.1 mg/kg s.c.). Administration of remoxipride by the i.v. or s.c. routes was more effective than by the i.p. route. FLA797(-), FLA908(-), and haloperidol were more effective than remoxipride in preventing the hypothermia caused by quinpirole, while NCQ436(-) was less effective than remoxipride. The variation in time of remoxipride's action and effectiveness in blocking the induced hypothermia followed the variations in plasma concentrations. The plasma concentrations of the active metabolites were below the limit of determination (< 2 nmol/l). Based on estimation of free brain concentrations at effective dose levels together with in vitro affinities for the DA D2 receptor it was concluded that the metabolites FLA797(-), FLA908(-), and NCQ436(-) do not appear to contribute to the antagonism of DA D2 mediated neurotransmission following a low remoxipride dose (1 mumol/kg).

Topics: Animals; Body Temperature; Chromatography, High Pressure Liquid; Dopamine D2 Receptor Antagonists; Ergolines; Haloperidol; Hypothermia; Male; Pergolide; Quinpirole; Rats; Rats, Sprague-Dawley; Remoxipride; Salicylamides

The effect of centrally and peripherally administered dopamine D1 and D2 specific compounds on core body temperature in mice was investigated. Quinpirole (LY-17155), a D2 agonist, induced a dose-dependent fall in body temperature (2.4-11.6%; p less than 0.003) when injected intraperitoneally (ip, 0.3-3.0 mg/kg) and intracerebroventricularly (icv, 0.1 mg/kg). This quinpirole-induced (1.0 mg/kg, ip) hypothermia was reversed by the central and peripheral administration of the D2 antagonists S-(-)-sulpiride (3.0-30.0 mg/kg, ip; 0.1-3.0 mg/kg, icv) and spiperone (0.03 and 0.1 mg/kg, ip; 0.03-3.0 mg/kg, icv). Domperidone, a D2 antagonist which does not cross the blood brain barrier, had no effect on quinpirole-induced hypothermia (1.0-10.0 mg/kg, ip). Domperidone partially reversed quinpirole-induced hypothermia at 0.1-30.0 mg/kg, icv. The D1 agonist, SKF-38393 at a high dose of 10.0 mg/kg, ip mildly attenuated quinpirole-induced hypothermia (a 1.8% increase in temperature). SKF-38393 at 10.0 mg/kg, icv potentiated quinpirole-induced hypothermia. SCH-23390 (0.1-3.0 mg/kg, ip), a D1 antagonist, had no effect on quinpirole-induced hypothermia and potentiated the hypothermia when administered icv. An ineffective icv dose of spiperone (0.01 mg/kg) in reversing quinpirole-induced hypothermia was rendered effective by prior administration of SCH-23390 (0.1-3.0 mg/kg, icv) but not by SKF-38393 (1.0-10.0 mg/kg, icv). These data suggest a central D2 receptor mechanism mediating hypothermia in mice which is capable of being modulated by the D1 receptor.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Benzazepines; Body Temperature Regulation; Cerebral Ventricles; Domperidone; Dopamine Agents; Dopamine Antagonists; Ergolines; Hypothermia; Injections, Intraperitoneal; Injections, Intraventricular; Male; Mice; Mice, Inbred ICR; Quinpirole; Receptors, Dopamine; Receptors, Dopamine D1; Receptors, Dopamine D2; Spiperone; Sulpiride

Our earlier studies showed that dihydropyridine calcium channel antagonists have some central pharmacological effects. Flunarizine is considered to be a calcium channel antagonist; therefore this study was aimed at investigating the effect of flunarizine (given in single doses of 5, 10 and 20 mg/kg p.o.) in behavioural models in which calcium channel antagonists of the dihydropyridine type were previously studied. Flunarizine inhibited the apomorphine-induced stereotypy and yawning behaviour in rats. It decreased the hypothermia induced by a low dose of apomorphine in mice, but not that one induced by high dose of it. The quinpirole-induced hypothermia was also reduced. In the tests used for evaluation of the effect on the serotonergic system, flunarizine decreased the 5-HTP-induced head twitches and partly antagonized the fenfluramine- and quipazine-induced hyperthermias (at a high ambient temperature). In the forced swimming test flunarizine was inactive in mice and rats. The obtained results indicate that flunarizine exerts central antagonistic effects on the dopaminergic and serotonergic systems and has no antidepressant activity. Flunarizine differs from calcium channel antagonists of the dihydropyridine type, which have no dopamine-antagonistic activity and show anti-depressant-like properties.

Topics: 5-Hydroxytryptophan; Animals; Apomorphine; Body Temperature Regulation; Dopamine; Dopamine Antagonists; Drug Interactions; Ergolines; Fenfluramine; Flunarizine; Hypothermia; Male; Mice; Motor Activity; Quinpirole; Quipazine; Rats; Rats, Inbred Strains; Serotonin; Serotonin Antagonists; Species Specificity; Stereotyped Behavior; Yawning

The nonselective dopamine (DA) receptor agonists R(-)apomorphine (APO) and R(-)-N-n-propylnorapomorphine (NPA) elicited dose- and time-dependent hypothermia in mice with ED50 values of 300 and 18 micrograms/kg, respectively. The selective D2 agonist quinpirole (LY 171555) also elicited dose-dependent hypothermia, whereas the selective D1 agonist SKF 38393 had no effect. The selective D1 and D2 antagonists SCH 23390 (1 mg/kg) and sulpiride (200 mg/kg), respectively, did not significantly alter body temperature. The hypothermic effect of a maximal dose of NPA (0.2 mg/kg) was not blocked by SCH 23390 (1 mg/kg) but was significantly attenuated (p less than 0.001) by pretreatment with sulpiride (200 mg/kg). Pretreatment with sulpiride (200 mg/kg) produced a parallel, 40-fold shift to the right of the dose-response curve for NPA. Partial, irreversible DA receptor inactivation by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) (2 mg/kg) reduced the maximal hypothermic effect of NPA (to 49% of control) without altering its ED50. Analysis of the data indicated a linear relationship between DA receptor occupancy and hypothermic response. The results demonstrate that DA agonist-induced hypothermia in mice is mediated by D2 receptors and that there is no receptor reserved for this response.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Adrenergic alpha-Antagonists; Animals; Apomorphine; Benzazepines; Body Temperature; Dopamine Agents; Dopamine Antagonists; Ergolines; Hypothermia; Male; Mice; Mice, Inbred Strains; Quinolines; Quinpirole; Receptors, Dopamine; Receptors, Dopamine D2; Sulpiride

The hypothermia induced by apomorphine, a mixed dopamine (DA) agonist in male Swiss-Webster mice, was not blocked by the selective D-1 antagonist SCH 23390 but was completely blocked by the selective D-2 antagonists haloperidol, sulpiride and YM-09151-2. The selective D-1 agonist SKF 38393 did not elicit hypothermic response but the selective D-2 agonist quinpirole caused a marked lowering of rectal temperature. D-2 antagonists blocked this response to quinpirole. SCH 23390 enhanced and SKF 38393 attenuated the hypothermia induced by quinpirole. Ineffective doses of haloperidol and SKF 38393, when given together, completely blocked the effect of quinpirole. It was concluded that hypothermia is a D-2 receptor mediated response but modulated by the D-1 receptor system. In another series of experiments the influence of neuroleptics and antidepressants on the hypothermic effect of apomorphine and quinpirole was investigated. The hypothermic effect of a low dose (1 mg/kg) of apomorphine was blocked by the D-2 receptor antagonists, but not by classical antidepressants. However, the response to a high dose (10 mg/kg) of apomorphine was blocked by both classical antidepressants and D-2 antagonists (except haloperidol). These drugs did not show similar effect on quinpirole-induced hypothermia. It is clear that the hypothermic response, especially that of quinpirole, is not a suitable model for testing either neuroleptics or antidepressants.

Topics: 2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; Animals; Anti-Anxiety Agents; Apomorphine; Benzamides; Benzazepines; Dopamine; Dopamine Antagonists; Ergolines; Haloperidol; Hypothermia; Male; Mice; Quinpirole; Receptors, Dopamine; Receptors, Dopamine D1; Receptors, Dopamine D2; Sulpiride

6-Ethyl-9-oxaergoline (EOE) and its enantiomers were compared with apomorphine in a number of tests designed to measure dopamine (DA) agonist activity within the central nervous system. In rats, the tests were: interaction with DA receptors labeled with 3H-apomorphine or 3H-spiroperidol; the effects on DA synthesis as assessed by the gamma-butyrolactone procedure; turning in 6-OHDA lesioned animals; stereotypy; and, slowing of DA cell firing rates. In the mouse, locomotor activity, hypothermia and postural asymmetry in caudectomized animals were studied. Emesis in the beagle was also examined. The (-)-enantiomer of EOE was more potent than either the (+)-enantiomer or the racemate in all tests. With the exception of inducing stereotypy and the displacement of 3H-apomorphine from rat striatal membranes, (-)-EOE was equi- or more potent than apomorphine in all test procedures. (-)-EOE was effective following oral administration and exhibited a longer duration of action than apomorphine. The results indicate EOE is a potent DA agonist.

Topics: 4-Butyrolactone; Animals; Apomorphine; Brain; Dopamine; Ergolines; Female; Humans; Hypothermia; Mice; Motor Activity; Rats; Rats, Inbred Strains; Receptors, Dopamine; Stereoisomerism; Stereotyped Behavior

The body temperature of rats has been studied in a cold environment. In this setting, bromocriptine induced hypothermia. This fall in core temperature was inhibited by pimozide. It was concluded that bromocriptine has a dopamine-like action in areas of the brain concerned with the control of body temperature, as has previously been shown for apomorphine and amphetamine.

Topics: Amphetamine; Animals; Apomorphine; Body Temperature Regulation; Brain; Bromocriptine; Cold Temperature; Colon; Dopamine Antagonists; Dose-Response Relationship, Drug; Environment, Controlled; Ergolines; Hypothermia; Male; Pimozide; Rats

Topics: Ergolines; Ergonovine; Ergot Alkaloids; Hyperkinesis; Hypothermia

Topics: Animals; Body Temperature; Claviceps; Ergolines; Ergot Alkaloids; Hyperkinesis; Hypothermia; Rats; Temperature