The experiment was aimed at investigating the relationship between reduced circulating/endogenous testosterone occasioned by orchiectomy and emotional behavior using the open field test. Eighteen male Wistar rats were randomly selected and classified into two groups: orchiectomized and nonorchiectomized. Orchiectomy was carried out by simple sham surgery. After recovery from orchiectomy, plasma testosterone was determined in both groups after which each animal was observed in the open-field for neurobehavioral activities. The result showed a significant (p <0.05) reduction in plasma testosterone concentration as well as the frequencies of novelty-induced neurobehaviors scored in the open field arena in the orchiectomized group when compared with the nonorchiectomized group. Results indicated that a reduction in circulating testosterone exerts behavioral deficits in orchiectomized animals in the form of fear imposed by exposure to a novel environment resulting in fewer activities. This observation was confirmed by the presence of testosterone receptors in specific brain areas associated with behavioral modulation. We therefore conclude that circulating testosterone could be one of the endogenous mechanisms responsible for coping with fear induced by exposure to a novel environment.
orchiectomy; testosterone; open field; fear; neurobehavior; amygdala
