Brain serotonergic neurons: their role in a form of dominance-subordination behavior in rats

The present study evaluated the possible role of brain serotonergic neurons in dominant-subordinate (D-S) behavior in Wistar male rats competing for water. Treatment of D rat with drugs that stimulate serotonergic neurons of receptors (tryptophan, 5-hydroxytryptophan, quipazine, femoxetine) resulted in D-S reversal. A similar effect was observed when the S animal was treated with drugs that blocked serotonin synthesis (p-chlorophenylalanine) or receptors (metergoline). The D-S relationship was unchanged when serotonergic drugs were given to the S subject (tryptophan or quipazine) or when D animal received p-chlorophenylalanine. None of the drugs tested influence the water intake and the general activity of rats. Rats with lesioned midbrain raphe nuclei were always dominant when paired with sham lesioned counterparts. Our results indicate that one form of dominance behavior can be inversely related to the activity of brain 5-HT system.