Acute in vivo exposure to fentanyl reduces GABA immunoreactivity in the CA1 area of the rat hippocampus

Abstract

The effect of in vivo fentanyl treatment on GABAergic immunoreactivity was studied in the CA1 area of the rat hippocampus. Animals were treated either with saline or fentanyl (4x80 μg/kg, s.c./15min). GABA immunohistochemistry revealed lower GABA content in processes and neuronal somata suggesting reduced GABA release onto pyramidal neurons. Thus, acute in vivo exposure to fentanyl may result in a long-lasting alteration in the excitability within the CA1 area of the hippocampus. These findings are in line with previously reported reduced GABA mediated transmission and may provide evidence regarding mechanisms involved in the early stages of tolerance development towards the analgesic effects of opioids. ©PHARMAKON-Press.