Tehran University Medical Journal

Background: Dopaminergic is the most important neurotransmitter is fear. The dopaminergic mesolimbic pathway has essential role in excitable behavior, and it's role in Parkinson disease. The aim of this research in study, the effect of dopaminergic pathway in fear response.
Methods: The elevated plus maze was used in combination with the percentage of time spent in the open arms of the maze (OAT%) and the percentage of entries into the open arms (OAE%) to measure fear. Increases in the OAT% and OAE% indicate an anxiolytic effect (reduction in anxiety), whereas decreases in the OAE% and OAT% indicate an anxiogenic effect. After five days, the rats were injected with saline and different doses of sulpiride and Bromocriptine.
Results: Results showed that intracerebroventricular administration of sulpiride, in the doses of 5, 20μg/rat and bromocriptine, D2 agonist in doses 65, 95μg/rat produced a significant effect comparing to sham groups (p<0.05). While intracerebroventricular administration of sulpiride 15, 10μg/rat, and bromocriptine 70, 80μg/rat, did not show any significant effect comparing with sham group (p<0.05). In the current research intracerebroventricular administration of sulpiride, D2 antagonist at the doses of 5, 10, 15, 20μg/rat and Bromocriptine, D2 agonist in the doses of 65, 70, 80, 95μg/rat were used and theire effect on the fear behavior were studied.
Conclusions: The possible effect of Dopaminergic system in the fear process, especially D2 receptor increase fear.