Inhibition of stress-induced dopamine output in the rat prefrontal cortex by chronic treatment with olanzapine.
BACKGROUND
Chronic exposure to stressful events precipitates or exacerbates many neuropsychiatric disorders, including depression and schizophrenia. Evidence suggests that treatment with the atypical antipsychotic drugs olanzapine or clozapine results in a superior amelioration of the anxious and depressive symptoms that accompany schizophrenia relative to therapy with classical antipsychotics such as haloperidol. Moreover, olanzapine and clozapine, but not haloperidol, increase the brain content of neuroactive steroids. The effects of olanzapine and clozapine on the stress-induced increase in dopamine output in the rat cerebral cortex have now been compared with that of haloperidol.


METHODS
Rats chronically treated (3 weeks, once a day) with each drug were exposed to foot-shock stress or injected with a single dose of the anxiogenic benzodiazepine receptor ligand FG7142, and dopamine release was then measured in the prefrontal cortex by vertical microdialysis.


RESULTS
Long-term administration of olanzapine or clozapine prevented or markedly inhibited, respectively, the increase in the extracellular dopamine concentration induced by foot shock; haloperidol had no such effect. Chronic olanzapine treatment also blocked the effect of FG7142 on dopamine output.


CONCLUSIONS
The reduction in the sensitivity of cortical dopaminergic neurons to stress shown to be elicited by treatment with olanzapine or clozapine may contribute to the anxiolytic actions of these drugs.
Dazzi
Laura
L
Department of Experimental Biology "B Loddo", Unit of Neuropsychopharmacology, University of Cagliari, Cagliari, Italy.
Seu
Emanuele
E
Cherchi
Giulia
G
Biggio
Giovanni
G
D000704:Analysis of Variance; D000818:Animals; D014150:Antipsychotic Agents / Q000008:administration & dosage*; D001569:Benzodiazepines / Q000008:administration & dosage*; D003024:Clozapine / Q000008:administration & dosage; D004298:Dopamine / Q000378:metabolism*; D015536:Down-Regulation; D004334:Drug Administration Schedule; D004597:Electroshock; D006220:Haloperidol / Q000008:administration & dosage; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D000077152:Olanzapine; D017397:Prefrontal Cortex / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013315:Stress, Psychological / Q000503:physiopathology*
D014150:Antipsychotic Agents; D001569:Benzodiazepines; D003024:Clozapine; D006220:Haloperidol; D000077152:Olanzapine; D004298:Dopamine