Role of opioid receptors in self-aggression in rats

Self-aggression is a behavioural disorder in which an individual damages its own body parts by intense biting or scratching. Self aggression has been reported in human patients in Lesch-Nyhan syndrome and in cases of schizophrenia, depression, and congenital analgesia. In human patients as well as in experimental animals some kind of dysesthesia of the part of the body that is mutilated has been suggested. This study was conducted to find out the underlying pain mechanisms in self-aggressive behaviour arising out of stereotypy. The study was performed in 40 adult male rats. In all these animals, self-aggression was produced as part of amphetamine induced stereotyped behaviour. A predetermined scale was used for quantifying this behaviour. Reserpine and phenoxybenzamine pretreatment led to an increase in the incidence of self-aggression. Naloxone administration in reserpine pretreated animals led to a further significant increase in the incidence of self biting as compared to controls. From these studies it appears that self-aggressive behaviour may be associated with increased pain sensation.