Spontaneous activity of dorsal raphe neurons during defensive and offensive encounters in the tree-shrew.

The general characteristic of these telemetrically recorded neurons of dorsal raphe, such as firing rate under nembutal anesthesia, reaction to illumination changes or acoustic stimuli were comparable to those in the literature. The firing rate of the dorsal raphe neurons increased during defensive encounters (+51% +/- 29% S.D.;p less than 0.005) and defensive fights (+ 113% +/- 91% S.D.;p less than 0.02) as compared to the neuronal activity of the undisturbed resting animal. The fearful interaction of the animal with the experimenter led to the strongest increase in the firing rate (+187% +/- 114% S.D.; p less than 0.002) in all animals tested. The offensive animal showed decreased neuronal activity during offensive encounters (-21% +/- 13% S.D.; p less than 0.02) and offensive fights (-42% +/- 17% S.D.; p less than 0.05) as compared with the neuronal activity of the undisturbed resting animal. These findings indicate the crucial importance of the animals appraisal of the situational contest for the activity of dorsal raphe neurons.