PubMed Health⌕ Search

Biomedical subjects

J M Koolhaas

Publications and source records attributed to J M Koolhaas.

118 records · Page 7Linked to original sources
PubMed1984

The corticomedial amygdala and learning in an agonistic situation in the rat.

Social agonistic behaviour of intact male rats is strongly reduced by the experience of defeat by a dominant male conspecific. Small electrolytic lesions in the corticomedial amygdala strongly affected this behavioural change due to defeat. No effects of the lesions were observed before and during the defeat. Some learning is still possible in corticomedial amygdala lesioned animals. A comparison of the effects of lesions made before the defeat with lesions made after the defeat revealed that the lesions primarily produce a retention deficit in social learning.

Aggression↗
PubMed1978

Hypothalamically induced intraspecific aggressive behaviour in the rat.

The effects of electrical stimulation of the lateral hypothalamus (LH) of rats on intraspecific aggressive behaviour were studied. In order to investigate the specificity of the stimulation effects, each experimental animal was stimulated in a number of different social situations. Stimulation of the LH in the presence of a subordinate male increased the amount of time spent on aggressive behaviour patterns and locomotion. In the presence of a dominant male, however, the stimulated animal never initiated a fight, whereas in the presence of an estrous female attack occurred in some rare occasions and sexual behaviour disappeared almost entirely. Stimulation of some sites also elicited mouse killing behaviour. Many of the electrodes that elicited intraspecific aggressive behaviour also supported intracranial self-stimulation. It is concluded that 1. electrical stimulation of this area of the LH predominantly potentiates intraspecific aggressive behaviour, 2. that this behaviour becomes overt depends on the external situation, including the behaviour of the opponent.

Aggression↗
PubMedDate not supplied

Changes in daily rhythms of body temperature and activity after a single social defeat in rats.

The long-term consequences of social stress on daily rhythms of body temperature and activity in rats were studied by means of radiotelemetry with intraperitoneally implanted transmitters. Rats were subjected to a single social defeat by placing them into the territory of a male conspecific for 1 h. Social defeat caused a sharp subsequent reduction in the amplitude of the daily temperature rhythm, which lasted for at least 4 days. The reduced amplitude was mainly due to higher temperatures during the circadian rest phase, i.e., the light period. Movement activity was less affected, but the decrease in activity during the dark phase after defeat correlated significantly with the temperature increase during the light phase. The stress-induced changes in daily rhythms of body temperature and activity are discussed in terms of their relevance to the role of rhythm-disturbances in the pathogenesis of affective disorders.

Animals↗
PubMedDate not supplied

A telemetry study on the chronic effects of microdialysis probe implantation on the activity pattern and temperature rhythm of the rat.

The present study describes the effects of implantation of microdialysis probes on temperature and activity rhythms of the rat, measured with a telemetry system. For comparison two widely used types of microdialysis probes were investigated, a transcerebral probe, inserted into the pineal gland and a set of two I-shaped concentric probes, implanted bilateral into the striatum. Starting from 5 days before the operation until 8 days after surgery, activity and temperature recordings were carried out continuously with the help of previously implanted transmitters. In separate experiments the effects of two different types of anaesthesia (chloralhydrate and Hypnorm) were determined. The results show that there is a pronounced effect of surgery on amplitude and rhythmicity of the temperature and activity patterns which is still detectable 6-7 days after operation. Few differences were noticed between the transverse probe and the I-shaped probes. Anaesthesia alone induced much smaller changes, most of which had disappeared within 2 or 3 days after the treatment. The duration of action of chloralhydrate is somewhat longer compared to Hypnorm. The conclusion is that when microdialysis is used in behavioural experiments, the effects of the surgical procedure should be taken into account. If these effects are serious, the use of previously implanted guide cannulae might be necessary.

Animals↗
PubMedDate not supplied

Prefrontal cortex and neostriatum self-stimulation in the rat: differential effects produced by apomorphine.

In a dose-response experiment, the effects of intraperitoneal injections of the dopamine receptor agonist, apomorphine (0.075, 0.15, 0.3, 0.6 and 1.2 mg/kg) were studied on self-stimulation elicited from electrodes implanted in the medial and sulcal prefrontal cortex and caudate-putamen in the rat. From the medial and sulcal prefrontal cortex electrodes, apomorphine produced a dose-related decrease of self-stimulation rate which was consistent across animals. From the caudate-putamen electrodes, on the contrary, apomorphine produced a facilitatory effect in the majority of the animals at one or more doses, however, at other doses a decreased self-stimulation rate was observed. The clear and consistent effects of apomorphine on self-stimulation of the prefrontal cortex, together with other experimental evidence in the same line, suggest that dopamine is mediating self-stimulation of this cortical area.

Animals↗
PubMedDate not supplied

Immunity in barren and enriched housed pigs differing in baseline cortisol concentration.

It was shown in a recent study [De Jong IC, Prelle IT, Van de Burgwal JA, Lambooij E, Korte SM, Blokhuis HJ, Koolhaas JM. Effects of environmental enrichment on behavioral responses to novelty, learning and memory and the circadian rhythm in cortisol in growing pigs. Physiol Behav, in press.] that barren housed pigs (small pens, no substrate) have a blunted circadian rhythm of salivary cortisol as compared to enriched housed pigs (large pens with daily fresh bedding). In the light period, enriched housed pigs showed significantly higher concentrations of cortisol in saliva than barren housed pigs, whereas in the dark period, cortisol concentrations were low in both enriched and barren housed pigs. In the present study, the immunological consequences of the difference in baseline salivary cortisol concentration in the light period were evaluated. It appeared that leukocyte and lymphocyte distributions, and in vitro lymphocyte proliferation following ConcanavalineA (ConA) stimulation in the assay using purified lymphocytes were not affected. However, barren and enriched housed pigs did show a different proliferation response to ConA in the whole blood assay. At day 2 of culture, proliferation was higher in barren housed pigs than in enriched housed pigs, whereas at day 4 of culture, proliferation was higher in enriched housed pigs than in barren housed pigs. Lymphocyte proliferation at day 2 of culture in the whole blood assay correlated negatively with plasma cortisol levels, which might thus explain the higher proliferation in barren housed pigs at day 2 of culture. The in vivo humoral and cellular (delayed type hypersensitivity, DTH) immune response to KLH was not affected by housing conditions. We conclude that, although baseline salivary cortisol concentrations differ between enriched and barren housed pigs, immune function appears to be relatively unaffected.

Animals↗
PubMedDate not supplied

Enhanced sensitivity of postsynaptic serotonin-1A receptors in rats and mice with high trait aggression.

Individual differences in aggressive behaviour have been linked to variability in central serotonergic activity, both in humans and animals. A previous experiment in mice, selectively bred for high or low levels of aggression, showed an up-regulation of postsynaptic serotonin-1A (5-HT(1A)) receptors, both in receptor binding and in mRNA levels, in the aggressive line [Brain Res 736 (1996) 338]. The aim of this experiment was to study whether similar differences in 5-HT(1A) receptors exist in individuals from a random-bred rat strain, varying in aggressiveness. In addition, because little is known about the functional consequences of these receptor differences, a response mediated via postsynaptic 5-HT(1A) receptors (i.e., hypothermia) was studied both in the selection lines of mice and in the randomly bred rats. The difference in receptor binding, as demonstrated in mice previously, could not be shown in rats. However, both in rats and mice, the hypothermic response to the 5-HT(1A) agonist alnespirone was larger in aggressive individuals. So, in the rat strain as well as in the mouse lines, there is, to a greater or lesser extent, an enhanced sensitivity of postsynaptic 5-HT(1A) receptors in aggressive individuals. This could be a compensatory up-regulation induced by a lower basal 5-HT neurotransmission, which is in agreement with the serotonin deficiency hypothesis of aggression.

Aggression↗