Changes of Neuropeptides in the Basal Ganglia of Hemiparkinsonian Rat Model

We used in situ hybridization histochemistry with synthetic oligonucleotide probes to examined the effects of unilateral 6-hydroxydopamine lesions (which eliminated tyrosine hydroxylase mRNA containing cells in mesencephalon) on enkephalin, dynorphin, and substance P mRNA exprssion in the striatum. The expression of tyroxine hydroxylase mRNA on ipsilateral substantia nigra pars compacta, which reflect dopamine activity, totally decreased for 2weeks after lesioning. After lesioning 1week, 2weeks, and 4weeks, a significant increase of the expression of enkephalin mRNA in ipsilateral to the lesioned striatum was observed (p<0.05). Substance P mRNA expressions were depressed significantly in ispsilateral to the lesioned striaturm, whereas enkephalin mRNA expressions were elevated in consecutive sections from striatal aresas in all rat model. The effect of lesions on dynorphin mRNA expressions in ipsilateral to the lesioned striatum less robust, but significant decreased tendency was observed (p<0.05). These data show that the expression of enkephalin, dynorphin and substance P mRNA is differentially regulated by mesostriatal dopaminergic system.

The effects of kainate-induced Seizure on the Opioid Peptide Gene Expression in Rat Hippocampus

In the rat hippocampal formation, the time-course and dose-response of the expression of enkephalin and dynorphin gene were examined after kainate (KA) treatment with in situ hybridization histochemistry. The KA induced enkephalin and dynorphin mRNA expression in hippocampus occurred mainly in the dentate gyrus. The enkephalin mRNA expression appeared at 3hour after KA injection, increased dramatically at 6hour, and then decreses. At 24hour after KA injection, the expression of enkephalin mRNA disappeared. The dynorphin mRNA expression appeared at once after injection and increased dramatically at 3hour. Unexpectedly at 6hour after injection, the expression was decreased, and then increased less than the 3hour expression. The increased pattern persisted to 24hour after injection. Unexpected result was also encounted in the experiment of KA dose-response of enkephalin mRNA and dynorphin mRNA. In the hippocampal formation, in contrast with other areas, low dosage (8mg/kg) of KA induced more significant expression of both genes than high dosage (16mg/kg) of KA.