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Biomedical subjects

B H Westerink

Publications and source records attributed to B H Westerink.

170 records · Page 10Linked to original sources
PubMed1976

Regional rat brain levels of 3,4-dihydroxyphenylacetic acid and homovanillic acid: concurrent fluorometric measurement and influence of drugs.

A concurrent semi-automatic fluorometric assay technique for 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), is described. The method is based on a rapid manually performed isolation of DOPAC and HVA on small columns of Sephadex G-10 followed by an automated fluorometric detection with a continuous flow system. DOPAC and HVA were measured in the corpus striatum, nucleus accumbens and olfactory tubercle of the rat, under normal conditions and after treatment with amphetamine, apomorphine, clozapine, haloperidol, morphine, oxotremorine, pargyline, probenecid, sulpiride and thioridazine. Clozapine, morphine, sulpiride and oxotremorine induced the most pronounced rise of DA metabolites in the nucleus accumbens. Probenecid produced a DOPAC accumulation in the nucleus accumbens. Striking differences were observed between the DOPAC/HVA ratios in the different structures of control animals. The concurrent assay enables a rapid screening of the action of drugs in regional DA metabolism.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1976

Comparison of effects of drugs on dopamine metabolism in the substantia nigra and the corpus striatum of rat brain.

The influence of apomorphine, chloral hydrate, haloperidol, morphine, oxotremorine, pargyline, probenecid and promethazine on DOPAC and HVA levels was studied in the substantia nigra (including the ventral tegmental dopaminergic regions) and corpus striatum of the rat brain. The time--effect curves of changes in HVA levels after pretreatment with apomorphine, haloperidol, morphine, oxotremorine or promethazine are presented. The time--effect curves for the substantia nigra showed an initial rapid HVA rise, which was not observed in the corpus striatum. Promethazine treatment caused a small but significant HVA rise in the substantia nigra only. Chloral hydrate, morphine and oxotremorine induced a similar percentage increase in DOPAC and HVA levels in the substantia nigra as well as in the corpus striatum. Haloperidol, however, caused a small percentage change in the metabolite levels in the substantia nigra when compared to the pronounced rise seen in the corpus striatum. The apomorphine-induced HVA decrease observed in both structures provides evidence for the presence of a dopaminergic receptor in the substantia nigra.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1976

Effects of drugs on the formation of homovanillic acid in the rat retina.

Homovanillic acid (HVA) levels were measured in the eye and the corpus striatum of rats under normal conditions and after different drug treatments. Neuroleptic agents such as clozapine, cis-flupenthixol and haloperidol induced comparable increases in HVA levels, whereas the non-neuroleptic trans-isomer of flupenthixol was inactive in both structures. Apomorphine decreased HVA levels in the retina and the corpus striatum, while amphetamine induced a decreased HVA formation in the retina and did not change levels of HVA in the corpus striatum. Probenecid caused a similar percentage rise of HVA in both structures. Morphine and oxotremorine induced a rise in HVA levels in the corpus striatum but not in retinal samples.

Amphetamine↗
PubMed1975

Influence of drugs on striatal and limbic homovanillic acid concentration in the rat brain.

Homovanillic acid (HVA) was measured in the corpus striatum aan the limbic structures nucleus accumbens and olfactory tubercle of the rat, under normal conditions and after different drug treatments. Clozapine, thioridazine, morphine and physostigmine induced a similar percentage HVA increase in the three brain structures studied. Haloperidol and pimozide induced a higher percentage increase of HVA in the corpus striatum and nucleus accumbens when compared with the olfactory tubercle. Oxotremorine induced the highest HVA levels in the nucleus accumbens. Probenecid induced a significantly higher percentage accumulation of HVA in the limbic structures, especially in the olfactory tubercle. The HVA rise seen after haloperidol was suppressed by pretreatment with p-chlorophenylalanine or amino-oxyacetic acid in all structures studied. After atropine or trihexylphenidyl treatment the HVA rise induced by haloperidol was slightly suppressed in the limbic structures only. Our results suggest that not only under normal conditions but also after treatment with various types of drugs, dopamine metabolism as reflected by the HVA levels, is closely related in the different rat brain structures.

Aminooxyacetic Acid↗
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↗