Modification of tetrabenazine effects following pain-induced aggression in rats

Pain-elicited aggression was measured in four groups of Wistar rats (five pairs per group) during four electric shock sessions (100 shocks per session, 1.3 mA, 0.5 sec duration). Two groups received injections of tetrabenazine and saline, respectively, 90 min before each session. In the other two groups tetrabenazine and saline injections were alternated before each session, one group starting with tetrabenazine and the other with saline. Tetrabenazine produced marked inhibition of the aggressive response, reducing its frequency to about 10% of saline levels. However, an initial experience of high aggression during a saline session significantly modified the tetrabenazine effects for subsequent injections, suppressing aggression to only about 40% of control values.