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Biomedical subjects

R G Fessler

Publications and source records attributed to R G Fessler.

At least 55 records · Page 3Linked to original sources
PubMed1983

Effects of lithium carbonate on serotonin uptake in rat blood platelets.

1. Lithium carbonate administration to male rats for 1 to 4 weeks increased the affinity of platelet serotonin (5-HT) uptake (decreased Km) and decreased the rate of 5-HT uptake (Vmax) when the serum lithium levels were 0.5 meq/1 to 0.65 meq/l. When the serum levels were increased further to 1 meq/1, Vmax decreased further, without additional change in Km. 2. No effect on the kinetics of 5-HT uptake was observed when serum lithium levels were at 0.4 meq/1 or below. 3. Addition of lithium carbonate in vitro (1 meq/1) had no effect on the Km and Vmax of rat platelet 5-HT uptake. 4. The possible mechanism of the inhibitory effect of lithium treatment on platelet 5-HT uptake is discussed.

Animals↗
PubMed1982

Behavioral effects of chronic phencyclidine administration in rats.

The development of tolerance to phencyclidine (PCP) was examined in rats using behavioral rating scales with simultaneous measurements of locomotor activity, stereotyped behaviors, and ataxia. Significant tolerance to the stereotyped behaviors and ataxia induced by 5 or 10 mg/kg PCP was found on day 5 of chronic drug treatment. Because ataxia interferes with PCP-induced locomotor activity (Sturgeon et al. 1979), tolerance to PCP-induced ataxia produced an increase in locomotor activity on day 5. Tolerance to the ataxia, but not to the stereotyped behaviors induced by PCP, was more prominent after day 15 of PCP administration than after day 5. Administration of PCP for 15 days resulted in significant decrease in locomotor activity for the 5 mg/kg group but not for the 10 mg/kg group. These results suggest that behavioral tolerance, rather than supersensitivity, develops after chronic PCP administration. The effects of PCP returned to baseline over a 14-day withdrawal period for rats treated with 5 mg/kg PCP for 15 days. Rats treated with 10 mg/kg PCP for 15 days still had not returned to baseline when tested 28 days after cessation of PCP treatment.

Animals↗
PubMed1982

Effects of lithium on behaviour induced by phencyclidine and amphetamine in rats.

d-Amphetamine and phencyclidine (PCP) have both been reported to produce manic-like sequela in humans, effects that are reportedly antagonized by lithium. To test the hypothesis that the acute effects of these drugs in rats may serve as models of mania, the behaviors induced by d-amphetamine (3 mg/kg) or PCP (5 mg/kg) were quantified on behavioral rating scales subsequent to chronic dietary pretreatment with lithium carbonate or control diet. On day 14 of pretreatment, PCP-induced stereotyped behaviors and ataxia were potentiated in rats receiving lithium (plasma levels 1.0 +/- 0.23 mEq/l). PCP-induced locomotor activity was not affected by lithium pretreatment. Stereotypies and locomotion induced by d-amphetamine were also not significantly affected by lithium pretreatment. These results suggest that neither PCP nor amphetamine administered acutely to rats will be useful models to explore the manic-like symptoms produced by these drugs in humans.

Animals↗
PubMed1981

A comparison of the effects of neuroleptics on phencyclidine-induced behaviors in the rat.

The dose-response effects of neuroleptic pretreatment on phencyclidine (PCP; 3 or 5 mg/kg)-induced locomotor activity, stereotyped behaviors and ataxia were quantified in groups of male rats using rating scales recently developed in this laboratory. Three butyrophenone neuroleptics consistently produced dose-dependent antagonism of the behavioral effects of PCP administration. Fluphenazine antagonized the behavioral effects produced by 3 mg/kg PCP but not those produced by 5 mg/kg PCP. Each of the other neuroleptics examined (chlorpromazine, thioridazine, mesoridazine, triflupromazine, cis-flupenthixol) had no consistent antagonistic effect or actually enhanced one or more of the behavioral effects of PCP. Some neuroleptics slightly reduced PCP locomotion or stereotypies at high doses, but these effects were probably a non-specific consequence of the synergistic ataxia-producing properties of these drugs. In a second set of experiments, atropine sulfate pretreatment increased PCP-induced locomotor activity and stereotyped behaviors but had no effect on ataxia; pretreatment with physostigmine produced opposite effects. Combined pretreatment with haloperidol and atropine sulfate significantly reduced only haloperidol antagonism of PCP-induced ataxia, thus suggesting that non-dopoaminergic effects of neuroleptics may interfere with their ability to antagonize PCP.

Animals↗
PubMed1980

Effects of phencyclidine and methylphenidate on d-amphetamine-induced behaviors in reserpine pretreated rats.

The effects and interactions of phencyclidine (PCP), methylphenidate and d-amphetamine on locomotor activity, stereotyped behavior and ataxia in reserpine- and vehicle-pretreated rats were examined. The behaviors of rats receiving PCP alone or in combination with other drugs were quantified along three dimensions (locomotor activity, stereotyped behavior, and ataxia) on scales developed in this laboratory. The behaviors of groups receiving methylphenidate and/or d-amphetamine in treatment combinations other than those including PCP were quantified using a well known d-amphetamine behavioral rating scale. PCP, methylphenidate and d-amphetamine each induced significant increases in locomotor activity and stereotyped behavior when administered alone. Reserpine was found to antagonize PCP-induced locomotor activity and stereotyped behavior, and methylphenidate-induced stereotyped behavior at a dose which either potentiated or had no significant effect upon d-amphetamine-induced behavior (depending upon the scale used). Reserpine also potentiated PCP-induced ataxia. Whereas PCP potentiated the locomotor activity induced by d-amphetamine in both reserpine- and vehicle-pretreated subjects, methylphenidate marginally antagonized d-amphetamine-induced stereotypy in reserpine-pretreated subjects. PCP-induced ataxia in reserpine pretreated subjects appeared moderately reduced in subjects also receiving d-amphetamine. In general, the behavioral effects of PCP appear to be more similar to those of methylphenidate than to those of d-amphetamine, but differences are also found between PCP and methylphenidate. The results are discussed in relation to a behavioral model recently proposed as a method for differentiating indirect dopamine agonists on the basis of their neurochemical mechanisms of action.

Animals↗
PubMed1979

Behavioral rating scales for assessing phencyclidine-induced locomotor activity, stereotyped behavior and ataxia in rats.

Behavioral rating scales were developed for quantification of phencyclidine (PCP)-induced locomotor activity, stereotyped behavior and ataxia in rats. The dose-response relationship for PCP-induced locomotor activity was found to be an inverted U-shaped function over the first 25 min after injection while over the last 30 min of the experiment the function was highly linear. A linear dose-response relationship was found for ratings of stereotyped behavior and ataxia throughout the 90 min period of observation. The ratings of these two behaviors were found to be closely parallel. The effects of PCP on locomotor activity were found to be greatest during those intervals when stereotyped behavior and ataxia were at moderate levels. Ratings of locomotor activity may be confounded by ataxia when PCP is administered alone or in combination with other drugs.

Animals↗
PubMed1978

Stimulation of rat prolactin secretion by indolealkylamine hallucinogens.

The hallucinogenic indoleamine drugs N,N-dimethyltryptamine (N,N-DMT), psilocybin, bufotenin, 5-methoxy-N,N-dimethyltryptamine, and N-methyltryptamine, increased rat plasma prolactin (PRL) levels. The increase in plasma PRL produced by N,N-DMT, psilocybin, and bufotenin was inhibited by methysergide, a serotonin receptor blocker. Parachlorophenylalanine (PCPA), an inhibitor of serotonin synthesis, significantly potentiated the increase in PRL produced by N,N-DMT, and psilocybin. Parachloroamphetamine, a relatively selective toxin for serotonin neurons, also stimulated the increase in PRL produced by N,N-DMT. These results suggest that the indole hallucinogens stimulate PRL secretion by a serotonergic agonist mechanism. Bufotenin has been reported to pass the blood-brain barrier poorly, but of the indoles studied it had the most potent effect on PRL secretion. This raises the possibility that the serotonin receptors which promote PRL secretion may be outside the blood-brain barrier or that the central 5-HT receptors which mediate PRL secretion may be especially responsive to bufotenin.

Animals↗
PubMed1977

Perlapine: relationship between stimulation of prolactin secretion and antipsychotic activity.

Perlapine is a dibenzohetereopine compound chemically related to clothiapine, loxapine, and clozapine. Although the latter three compounds are antipsychotic, perlapine has not been reported to be antipsychotic. Nevertheless, all four drugs increase rat plasma prolactin levels. The order of potency is loxapine, perlapine, clothiapine, and clozapine. These results suggest that either perlapine should be reexamined for antipsychotic properties or there are hitherto unsuspected discrepancies between the dopamine receptors relevant to antipsychotic activity in man and those that regulate prolactin secretion in the rat.

Animals↗
PubMed1977

Lysergic acid diethylamide: evidence for stimulation of pituitary dopamine receptors.

Lysergic acid diethylamide (LSD), 0.05 mg/kg and 0.20 mg/kg, significantly decreased plasma prolactin (PRL) levels in male rats. LSD, 0.20 mg/kg, also inhibits the increase in plasma PRL levels produced by chlorpromazine (CPZ), 5 mg/kg, and alpha-methyl-paratyrosine (AMPT), 50 mg/kg, both of which interfere with dopaminergic inhibition of PRL secretion. LSD was more potent than methysergide, a serotonin receptor blocker, in lowering plasma PRL levels and more potent than apomorphine, a known direct acting dopamine agonist, in blocking the increase in plasma PRL produced by quipazine, a 5-HT agonist. These results suggest LSD has potent dopamine agonist properties on the rat pituitary or hypothalamic dopamine receptors which directly or indirectly inhibit PRL secretion.

Animals↗
PubMed1977

Gonadectomy and sensitivity to electric shock in the rat.

The effects of gonadectomy and hormone replacement on sex-typical responses to electric shock were assessed using a modification of the flinch-jump technique. Ovariectomy increased body weight but had no effect on any measure of sensitivity to shock. Gonadectomy in males at any age resulted in reduced weight gain but the effect of gonadectomy on shock thresholds in males varied with the age of operation: neonatal gonadectomy increased sensitivity to shock as reflected in lower thresholds on all measures; adult gonadectomy did not reliably affect any shock threshold and castration at 7 weeks of age lowered only flinch and shuffle thresholds without affecting jump thresholds. However, testosterone injections elevated shock thresholds depressed by gonadectomy and this effect was most evident in the neonatally castrated group. Hence, it is doubtful that neonatal gonadectomy removes an organizational influence of testicular hormones on pain sensitivity. Moreover, changes in body weight and reactivity to shock following gonadectomy can occur in a relatively independent fashion.

Animals↗