Abstract
Methamphetamine (MA) addicts have been reported to reveal a deficit in cognitive performance, which is related to the function of the prefrontal cortex. Although it is well known that the medial prefrontal cortex (mPFC) in rats, which is crucial for cognitive function, shows long-term potentiation (LTP) in the projections from the hippocampus, there is no study on the influence of MA on synaptic plasticity of the hippocampal-mPFC pathway. In the present experiments, using sodium pentobarbitone-anesthetized rats, we investigated the effect of repeated MA treatment (4 mg/kg, 4 days, i. p.) on hippocampus-induced LTP in the mPFC. In MA-treated rats, LTP in the hippocampal-mPFC pathway was occluded compared with saline-treated rats. To further investigate this MA-induced reduction of LTP in the hippocampal-mPFC pathway, we administered D1 and D2 antagonists prior to MA injections. The MA-induced occlusion of hippocampal-mPFC LTP was prevented by D1 but not D2 antagonists. These findings suggest that D1 but not D2 receptors have a significant role in the MA-induced deterioration of synaptic plasticity in the hippocampal-mPFC circuits. (This work was supported by a grant from the Japan Health Sciences Foundation.) [Jpn J Physiol 54 Suppl:S248 (2004)]
