Effects of histamine agents on methamphetamine-induced stereotyped behavior and behavioral sensitization in rats.

In this study, effects of histamine (HA) agents on methamphetamine (METH)-induced stereotyped behavior and behavioral sensitization were examined in rats. Pretreatment with a precursor of HA, L-histidine (750mg/kg), significantly inhibited the METH (3 mg/kg)-induced stereotyped behavior, whereas pretreatment with an inhibitor of HA synthesis, alpha-fluoromethylhistidine (FMH) (100 mg/kg), an H1 antagonist pyrilamine (5 mg/kg) or an H2 antagonist zolantidine (5 mg/kg) enhanced it. The inhibitory effect of L-histidine on METH-induced stereotyped behavior was significantly blocked by coadministration of pyrilamine and zolantidine, indicating that the effect is mediated through H1 and H2 receptors. Moreover, chronic treatment with METH (3 mg/kg) significantly enhanced stereotyped behavior at the rechallenge with METH (1 mg/kg). Chronic treatment with L-histidine (750 mg/kg) plus METH inhibited the METH-induced argumentation of stereotyped behavior, while that with FMH (100 mg/kg), pyrilamine (5 mg/kg) or zolantidine (5 mg/kg) potentiated it. These findings suggest that the HA neuron system has an inhibitory role in METH-induced stereotyped behavior and behavioral sensitization.