Effects of locus coeruleus stimulation on muricide in olfactory bulbectomized and raphe lesioned rats

In order to elucidate the role of central monoamines in muricide of the rat, the effects of electrical stimulation of the locus coeruleus (LC) were investigated on two types of muricide induced by olfactory bulbectomy (OB rats) and midbrain raphe lesions (raphe rats). Muricide was inhibited in 71.4% of the OB rats by bilateral LC stimulation and in 26.7% by unilateral stimulation. Even in the rat in which muricide was not inhibited following LC stimulation, muricide was almost invariably suppressed by LC stimulation after pretreatment with pargyline. The antimuricidal effect of LC stimulation was partially blocked by administration of propranolol, but not by phenoxybenzamine. In contrast, muricide was inhibited by bilateral LC stimulation in 44.4% of the raphe rats, but this effect was not potentiated by pretreatment with pargyline. On the other hand, muricide was not significantly inhibited by either dorsal raphe or medial raphe stimulation in any OB rats. These results suggest that noradrenaline plays a more important role in inhibiting muricide in OB rats than in raphe rats.