Social isolation does not alter brain regional benzodiazepine binding site numbers, affinity and coupling in the rat.

Male Sprague-Dawley rats were differentially housed for 21 days immediately after weaning. Isolated animals showed a selective suppression of exploration of the light side of a two compartment box; spending significantly less time in the light, and making fewer transitions between the light and dark compartments compared to socially reared controls. However, both basal and GABA-stimulated [3H] flunitrazepam binding was unaltered in the frontal cortex, hippocampus, amygdala and cerebellum following social isolation. These results are discussed in relation to other studies on central benzodiazepine receptor changes following a variety of experimental stressors.

Mesocestoides corti: parameters of infection in CBA/Ca mice and the effect of introducing a concomitant trematode infection.

CBA/Ca mice infected with the tetrathyridia of Mesocestoides corti were exposed to Schistosoma mansoni cercariae either simultaneously, or at varying intervals after the initial M. corti infection. Cohorts were infected with either parasite alone. The dual infected mice and the mice harbouring M. corti alone were significantly heavier than either naive controls or mice carrying the S. mansoni infection only. The livers and spleens from dual infection mice were also found to be significantly heavier than those from other groups. Free M. corti tetrathyridia were reduced in number in the peritoneal cavity of dual infected mice, as compared with mice harbouring a single infection. Furthermore, the intensity of the initial M. corti infection, as measured by the number of capsules surrounding parasites in the liver, was reduced when the mice experienced an S. mansoni infection 21 days later. The mice which were exposed to M. corti only exhibited more mast cells and eosinophils around encapsulated tetrathyridia in the liver than did dual infection mice, while cells surrounding S. mansoni egg granulomas in the liver were significantly increased in dual infection mice. An increase in serum alkaline phosphatase levels was detected in both the mice receiving the dual infection and the mice with the S. mansoni only infection, but not in mice harbouring M. corti alone.

Deficits in exploratory behaviour in socially isolated rats are not accompanied by changes in cerebral cortical adrenoceptor binding.

Social isolation of rats produces marked deficits in exploratory behaviour in a novel environment. To test our hypothesis that adrenoceptors are modified by social isolation we have measured alpha 2- and beta-adrenoceptor binding in the cerebral cortex of rats isolated for 21 days starting immediately after weaning. After this period the animals showed a significant reduction in exploration in the elevated X-maze and increased avoidance of bright light in a two-compartment shuttlebox. There were no changes in adrenoceptor binding at this time, however. The implications of these findings are discussed.

Reduction in striatal 5-hydroxytryptamine turnover following chronic administration of ethanol to rats.

Male Sprague-Dawley rats were given 10% (v/v) ethanol to drink for 28 days and the effects of the drug on the brain 5-hydroxytryptamine (5-HT) turnover were studied. Turnover was decreased in the corpus striatum after ethanol treatment due to a decrease in 5-hydroxyindol-3-ylacetic acid (5-HIAA), and an increase in 5-HT, concentration. Noradrenaline concentration was also increased in this region, but those of dopamine and GABA were similar to control values. Ethanol had no effect on any of the neurotransmitters studied in the brain stem and hippocampus, nor on the activity of monoamine oxidase type A (MAO-A) and 5-HT uptake in the three brain regions. Chronic ethanol administration caused a selective decrease in striatal 5-HT turnover which was unrelated to either its rate of inactivation, or the activity of other brain neurotransmitters. These findings are discussed in relation to those obtained in previous studies.

An improved fluorimetric assay for brain monoamine oxidase.

A fluorimetric assay for monamine oxidase that uses kynuramine as the substrate is described. This method is more economic, rapid, reproducible, and sensitive than other similar procedures. Its validity has been confirmed by the study of the subcellular distribution, the effects of inhibitors, and the kinetics of enzyme activity. Previous reports of substrate inhibition by kynuramine may have to be reassessed in the light of evidence presented here.

Analysis of six serum components from rats infected with tetrathyridia of Mesocestoides corti.

The serum from rats infected intraperitoneally (i.p.) and subcutaneously (s.c.) with the tetrathyridia of Mesocestoides corti was analysed for alpha-amylase, alkaline phosphatase, gamma-glutamyltransferase, glucose, corticosterone and total proteins. A histochemical analysis for hepatic alkaline phosphatase was also carried out. A significant decrease in activity of serum alkaline phosphatase was detected in both the i.p. and s.c. infections, whereas a large increase in hepatic alkaline phosphatase was observed in i.p. infections. A significant increase in serum corticosterone was found in both the i.p. and s.c. infections. No changes were detected in the other four components. The relevance of these findings is discussed with respect to the host-parasite relationship.

Involvement of 5-hydroxytryptamine in the analgesic action of pethidine and morphine in mice.

1 Groups of mice were pretreated with the 5-hydroxytryptamine (5-HT) depletors, fenfluramine or p-chlorophenylalanine (PCPA), followed by pethidine or morphine. 2 Fenfluramine alone produced a short lasting analgesia but PCPA was without any effect. 3 Pethidine and morphine both increased hot plate reaction times measured after 30 min. 4 Pretreatment with PCPA attenuated morphine analgesia but did not affect pethidine analgesia. Fenfluramine did not alter the response to either analgesic. 5 PCPA produced a significant depletion of brain 5-HT levels which was not reversed by the analgesics. The fenfluramine-induced decrease in 5-HT was reversed by morphine but not by pethidine. 6 The results support the involvement of 5-HT in the antinociceptive action of morphine in the mouse.

Effects of pargyline and SKF-525A on brain N,N-dimethyltryptamine concentrations and hyperactivity in mice.

Mice pretreated with the monoamine oxidase inhibitor pargyline showed a dose-dependent increase in hyperactivity for up to 2 h following injections of N,N-dimethyltryptamine (DMT: 0.5-8.0 mg/kg). Hyperactivity was related to a linear increase in whole brain concentrations of DMT as measured by a new sensitive gas chromatographic assay. The duration of this behaviour paralleled the concentration of DMT in the brain from 15-120 min. However, at 15 min, there was no significant difference in brain DMT concentrations between mice receiving pargyline and those given distilled water at the two dose levels of DMT studied (2.0 and 8.0 mg/kg). Pre-treatment with the microsomal enzyme inhibitor SKF-525A, alone or in combination with pargyline, had no effect on the DMT-induced behaviour or on the brain levels of DMT.