Pretreatment with MK-801 inhibits pemoline-induced self-biting behavior in prepubertal rats.

The indirect dopamine agonist, pemoline (120-300 mg/kg s.c.), can induce self-biting behavior in the rat. The present study demonstrates that the non-competitive N-methyl-D-aspartate (NMDA) antagonist, dizocilpine (MK-801, 0.2 mg/kg s.c.), significantly attenuates pemoline-induced self-biting behavior, while simultaneously increasing locomotor activity. When animals received a fixed dose of MK-801 with increasing doses of pemoline, a competitive relationship emerged such that high-dose pemoline surmounted the antagonistic effect of MK-801. In contrast to spiperone, delayed administration of MK-801 was ineffective in blocking the subsequent expression of self-biting behavior, suggesting that dizocilpine exerts its protective effect early in the cascade of events which eventually leads to self-biting behavior in this paradigm.