Biomedical subjects

A.R. Cools

Publications and source records attributed to A.R. Cools.

3 recordsLinked to original sources

PubMed1996

The influence of social structure on social isolation in amphetamine-treated Java monkeys (Macaca fascicularis).

Amphetamine-induced social isolation in monkeys has often been considered a valid animal model for certain negative symptoms of schizophrenia. However, there appear to be many ambiguities in relation to the exact nature of the isolation. Therefore, the effect of orally administered amphetamine (AMP) on the occurrence of social isolation in Java monkeys was studied. In part I the rank dependency of the effects of AMP (0.5mg/kg) was investigated in four alpha-males and three beta-males. AMP increased 'proximity' and 'passive groom', and decreased 'active allogroom' in alpha-males. In contrast, AMP decreased all three behavioural elements to a certain extent in beta-males. It is concluded that AMP induces social isolation in beta-males, but not in alpha-males. In part II of this study the AMP-induced behaviour of the treated monkey and the simultaneously occurring changes in the non-treated monkeys were investigated in a detailed study of a single social group. AMP significantly reduced the frequency of 'exploration', 'locomotion', 'self-groom', 'swing', 'active groom', 'inspect', 'approach' and originally-present stereotypies. Thus AMP apparently reduces the ability to initiate behaviour which is characteristic for the adult animal. AMP did not affect the frequency of 'present' and 'play' and enhanced that of 'aggression' and 'fear' in the beta-male; it also elicited various juvenile-like behaviours in both alpha- and beta-males, suggesting that AMP induces a behavioural regression. Furthermore, the behaviour of the non-treated monkeys of the group was decisive for the occurrence of social isolation of the treated monkey. Thus, the effects of AMP on the social behaviour of Java monkeys depend on the individual sensitivity, the social position which the subject occupies in its group, and the behaviour of the partners of the treated subject.

Journal Article↗

PubMed1995

Differential ethanol intake in high and low responders to novelty.

The aim of the study was to determine whether high responders (HR) and low responders (LR) to novelty, selected from an outbred Wistar rat population, show differences in ethanol consumption. HR and LR differ in catecholaminergic activity in the nucleus accumbens as well as in brain sensitivity to corticosteroids, biological features believed to play a role in ethanol consumption. Due to these differences it was predicted that HR would consume less ethanol and show less preference than would LR. Animals were maintained on a schedule of alternative day presentation of ethanol. Starting with an ethanol presentation of 2% in a free choice with water, ethanol solutions were presented and increased by increments of 1% every second day. HR showed a preference for water over ethanol, whereas LR showed no preference for water over ethanol. In order to determine intake and preference stability, animals were switched to daily presentations of ethanol and maintained on a 10% ethanol solution for 18 days. Individual-specific differences remained stable throughout the entire period. Given the available knowledge about biological differences between HR and LR, the present data indicate that these animals are good models for the study of the mechanisms underlying individual-specific differences in the behavioral responses to ethanol.

Journal Article↗

PubMed1990

Animal models with construct validity for schizophrenia.

Developing animal models for psychiatric disorders is a complicated process. This is principally due to our relatively limited knowledge of the processes underlying such complicated illnesses as depression and schizophrenia. Unfortunately this can lead to a vicious circle. Our limited knowledge of the disease leads to the inability to develop proper animal models, which will lead to an inability to increase our knowledge about neuronal mechanisms underlying the illness. In the present review we have tried to show that with respect to schizophrenia the situation is slowly changing. Using electrophysiological and psychological methods, clinicians begin to understand the psychopathological processes underlying the schizophrenic process. Preclinical researchers have tried to use this knowledge to develop animal models in which hypotheses can be tested and possible insight into mechanisms underlying the disease can be gained. In the present review three different animal models are presented. These are based on the construct that schizophrenic patients are disturbed in their information processing. More precisely the first two animal models are based on the construct that schizophrenic patients are less able to differentiate between relevant and irrelevant stimuli. The analysis of the literature suggests that the amphetamine-induced distruption of latent inhibition (and probably blocking), and the phencyclidine-induced disturbances in the startle response might provide two interesting animal models with construct, face and predictive validity for schizophrenia. This third model deals with the amphetamine-induced changes in the behaviour of socially living monkeys. This model seems to be related to both positive and negative symptoms of schizophrenia and is based on the construct that the negative symptoms are due to a compensatory mechanism which protects the subjects from "sensory flooding". The amphetamine-induced changes in behaviour of socially living monkeys seem to represent an example of an animal model in which both positive symptoms (stereotypy) and negative symptoms (social isolation) occurs. The construct validity of this model is still unclear, but pharmacological studies suggest that, apart from the face validity, the model also has a certain predictive validity. The models discussed in the present review can help us to increase our insight in neuronal structures underlying information processing disturbances. Structures known to be implicated in these models include the hippocampus, amygdala and ventral striatum.

Journal Article↗