[Shock-induced aggression and reactivity following raphe lesion in rats. Effects of physostigmine (author's transl)]

Shock-induced fighting behavior, flinch-jump thresholds and locomotor open-field activity were studied following dorsal and medial raphe lesions in rats. Attack scores were raised for low-intensity shocks (1 mA) only, whereas they remained unchanged for shocks of higher intensity (2 mA), as compared to controls. The jump threshold is decreased in raphe lesioned animals, but the flinch threshold is unchanged. Physostigmine (0,2-0,5 mg/kg) reduces the lesion-induced hyperreactivity: locomotor open-field activity is reduced to a greater extent than in the controls, and habituation to the open-field situation is restored. Doses of physostigmine (e.g. 0,2 mg/kg), that do not modify shock-induced aggression in controls, reduce aggression in lesioned animals to the level shown by controls for low-intensity shocks. In conclusion, shock-induced aggression is not directly dependent on a serotonergic brain mechanism. The behavioral changes observed are related to the hyperreactivity induced by raphe lesions. This hyperreactivity presumably results from a reduced activity of cholinergic brain mechanisms.