Benzodiazepines preferentially affect mesolimbic dopamine turnover in rats.
Withdrawal of benzodiazepines in man may induce hallucinatory symptoms and can evoke delusional depressions, which can be treated with dopamine-antagonistic drugs. Withdrawal of benzodiazepines in rats induces a strong hyperactivity during daytime, leaving the nighttime activity relatively undisturbed. This hyperactivity may be related to an enhanced dopaminergic activity in the mesolimbic area, especially in the nucleus accumbens. Mesolimbic dopaminergic activity may be specifically involved in the development of benzodiazepine withdrawal. Acute administration of benzodiazepines in otherwise non-treated rats, has been described not to affect the dopamine-turnover in the nucleus accumbens, measured by synthesis inhibition. However, activation by administration of haloperidol (feedback activation) can be suppressed by benzodiazepines effectively. Five different benzodiazepines viz. desmethyldiazepam (DMD), lorazepam (LRZ), brotizolam (BTZ), triazolam (TRZ) and flunitrazepam (FNZ) have been compared with respect to their acute effects. Using a 3-fold increase in dopamine turnover (determined by measuring the DOPAC-concentration), benzodiazepines were capable to reduce this increase maximally for 70-80% in the nucleus accumbens. The results point to a selective effect of benzodiazepines in the nucleus accumbens. The increase induced by haloperidol in the corpus striatum was found to be much less sensitive to benzodiazepines. In contrast to the other compounds lorazepam appeared to have no effect on haloperidol-induced increase in DOPAC concentration. Flunitrazepam and brotizolam did affect not only the haloperidol-induced DOPAC increase but also the basal DOPAC concentrations. Linear dose-response curves could not be obtained for the compounds, but minimal effective doses could be assessed. Flunitrazepam and triazolam appeared to be the most active compounds.(ABSTRACT TRUNCATED AT 250 WORDS)
Laboratory for Medicines and Medical Devices, National Institute for Public Health and Environmental Protection, Bilthoven, The Netherlands.
J W
JW
van der Laan
L
L
Eigeman
C
C
Jansen van 't Land
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology*; D001569:Benzodiazepines; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005246:Feedback; D008032:Limbic System / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009714:Nucleus Accumbens / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D014151:Anti-Anxiety Agents; D015102:3,4-Dihydroxyphenylacetic Acid; D001569:Benzodiazepines; D004298:Dopamine