Tehran University Medical Journal

Background: Anxiety is a complex phenomenon with important results. In fact anxiety is a biologic process that has repetitive biological and physiological effect on the biological structure of brine. From long time ago anxiety and fear has bean one of the important psychological issues and for the control of anxiety different drugs with different mechanisms have been presented and understanding mechanisms that are involved lead us to newer drugs discovery. In this research the effect of morphine on the anxiety in the adult Male rats in the Ventral Tegmental area (VTA) and Nucleus Accumbens (NAc) was studied.

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 anxiety. Increases in the OAT% and OAE% indicate an anxiolytic effect (reduction in anxiety), whereas decreases in the OAE% and OAT% indicate an anxiogenic effect. Adult male rats, weighing 200-240 grams, underwent surgery. After five days, the rats were injected with saline and three different doses of morphine (2.5, 5, and 7.5 µl/rat). Experiment one included the injections into the VTA. In the second experiment, these injections were in the NAc. Behavioral tests were conducted between 12 pm and 4 pm and each animal was used once for each experiment.

Results: In the first experiment, although these doses of morphine injected into the TVA had no effect on the OAE%, a dose of 5µl/rat increased the OAT%, showing a decrease in the animals' anxiety. In the second experiment, doses of 2.5µl/rat injected into the NAc induced a significant increase in the OAT% and OAE%, there by displaying decreased anxiety in the animal. However, no significant change in the activity of the animals was observed.