Region-specific effects of chronic lithium administration on neuropeptide Y and somatostatin mRNA expression in the rat brain.

The aim of this study was to examine the effects of 4-week lithium (Li+) food supplementation on neuropeptide mRNA expression in the rat brain. In situ hybridisation was used to determine the effects on the expression of neuropeptide Y (NPY) and somatostatin (SS) mRNA. Increases in NPY mRNA levels were seen in the hippocampus, layers II-III of the entorhinal cortex, nucleus accumbens shell and in the medial caudate-putamen. Increases in SS mRNA expression were seen in the layers IV-VI of the entorhinal cortex and in the lateral caudate putamen. Thus, Li+ appears to affect discrete populations of NPY and SS mRNA expressing neurons, with possible relevance to beneficial effects of Li+ in affective disorders.