Effects of chemogenetic regulation of CaMKⅡα positive neurons in the ventral hippocampus on working memory impairment in the hemiparkinsonian rat.

Neurons expressing Ca2+/calmodulin-dependent protein kinase Ⅱα (CaMKⅡα) in the ventral hippocampus (vHIP) play a crucial role in working memory. However, its role in Parkinson's disease (PD)-related working memory impairment remains unclear. In the present study, PD model was established by unilateral lesions of the medial forebrain bundle (MFB) by 6-hydroxydopamine in rats. The effects of chemogenetic activation or inhibition of CaMKⅡα positive neurons in the vHIP on working memory, theta (θ) rhythm of the medial prefrontal cortex (mPFC) and levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) in the dorsal hippocampus (dHIP), vHIP and mPFC were observed in sham and the lesioned rats. The results indicated that neither chemogenetic activation nor inhibition of CaMKⅡα positive neurons in the vHIP influenced the working memory, the peak θ rhythm of the mPFC or the levels of DA and 5-HT in the dHIP, vHIP and mPFC in sham rats. In the MFB lesioned rats, activation of CaMKⅡα positive neurons in the vHIP ameliorated the working memory impairment, increased peak of θ rhythm of the mPFC and increased the levels of DA in the dHIP, vHIP and mPFC. While, inhibition of CaMKⅡα positive neurons exacerbated working memory impairment, reduced the peak of θ rhythm of the mPFC and decreased the levels of 5-HT in the mPFC. These results suggest vHIP CaMKⅡα neurons regulate PD-related working memory impairment in rats, possibly via altered peak of θ rhythm of the mPFC and monoamine levels in related brain regions.