Effects of heroin dependence on the expression of SP and NPY in the VTA and NAc regions of rat brain

Abstract

In previous studies from our laboratory, heroin use has been shown to cause abnormal expression of several neuroendo‐peptides in the nervous system and other organs. In the present study, the expression of substance P (SP) and neuropeptide Y (NPY) was examined in the ventral tegmental area (VTA) and nucleus accumbens (NAc) regions of rat brain after heroin use. Rats were chronically treated by subcutaneous injection of heroin for up to 38d. Immunohistochemical staining was performed to test the expression of SP and NPY in the VTA and NAc regions. The results revealed that the expression of SP and NPY was observed as brown yellow particle in the cytoplasm of neurons in the VTA and NAc regions. Furthermore, SP‐immunoreactive cells and NPY‐immunoreactive cells expressed less SP and NPY in the VTA and NAc regions from heroin dependence rats than that from saline control and normal control rats at different time points. Immunohistochemical analysis showed higher grey value was found in heroin dependence rats than that in controls (p<0.05). The findings highlight the secretion of SP and NPY is inhibited during heroin dependence and it may result in the inhibition of endogenous opioid peptides, suggesting that SP and NPY may be key molecules during drug addiction.