Effect of caerulein with haloperidol on monoamine contents in rat brain regions treated with methamphetamine.

To elucidate the mechanism of the antagonistic effect of caerulein on amphetamine-induced hyperactivity, monoamine contents in rat brain regions were measured by HPLC. With a combination of caerulein and haloperidol, dopamine contents in methamphetamine treated-rats were significantly decreased in the striatum. Noradrenaline contents were significantly decreased in the haloperidol-methamphetamine group, but caerulein restored it to the normal levels. Serotonin contents did not change in any of the groups tested. These results may indicate that caerulein acts as a neuromodulator in rat brain and causes suppression of hyperactivity induced by methamphetamine.