Subordination induced decrease in 5-hydroxytryptamine and dopamine levels in the frontal cortex--a study using worker-parasite relationship in rats as a model.

Competition for a limited resource appears to be an important factor in natural selection. Such competition when elicited experimentally, leads to the establishment of dominant-subordinate (D-S) relationship between the competitors. The present study was carried out to analyse the effect of D-S relationship on the levels of monoamines, namely, dopamine (DA), 5-hydroxytryptamine (5-HT) and norepinephrine (NE) in various brain regions. The model of D-S relationship selected for this work was a modified worker-parasite paradigm in adult male Wistar rats. The levels of monoamines were estimated in the frontal cortex, the entorhinal cortex, the hippocampus and the septum of the two competitors and a non-competitor control, using high pressure liquid chromatography (HPLC). Levels of DA and 5-HT, but not NE, were found to be lower (P < 0.05) only in the frontal cortex of the subordinate as compared to that of the dominant or the control. These findings are comparable with similar neurochemical changes reported to be caused by some of the known stressors.