Scopolamine prevents the development of sensitization to methamphetamine.

The cholinergic neurotransmission has been implicated in various forms of neural plasticity such as kindling and learning. The present study examined the effects of scopolamine, a muscarinic cholinergic antagonist, on the development of behavioral sensitization to methamphetamine (MA). Rats treated with MA (1 mg/kg, sc) for 10 days indicated significantly enhanced motor activity when tested with MA (0.5 mg/kg) after a 7-8 day withdrawal, indicating the development of behavioral sensitization. Pretreatment with scopolamine (3 mg/kg) prior to MA administration prevented the development of the phenomenon. Rats treated with scopolamine alone showed no difference in the motor activity compared to those treated with saline. These results suggest that stimulation of muscarinic cholinergic receptors plays a role in the development of behavioral sensitization.