The increase of intrinsic excitability of layer V pyramidal cells in the prelimbic medial prefrontal cortex of adult mice after peripheral inflammation

Symptoms including depression and hypofunction of cognitive and decision-making are commonly associated with chronic pain. Recent studies have shown that the state of the medial prefrontal cortex (mPFC) neurons is important in diverse high-order cognitive and emotional activity in animals and humans. The mPFC layer V neurons mainly integrate information from other brain areas. The abnormal activity and function of pyramidal neurons influence the signal processing in the mPFC. Here we observed the changes of the excitability of the prelimbic mPFC neurons by whole-cell current-clamp recordings in adult mouse with inflammatory pain induced by complete Freund's adjuvant (CFA). Results showed that resting membrane potential and membrane input resistance did not differ between CFA-treated and control animals. Single action potential (AP) did not differ in terms of amplitude, but rheobase, half AP duration, and decay time were significantly decreased, and voltage threshold was more hyperpolarized in CFA group. Although the firing adaptation did not differ in two groups, the repetitive AP firing number and initial firing rate were significantly increased in CFA group. These data suggest that the increase in the intrinsic excitability of prelimbic mPFC layer V pyramidal neurons may be involved, at least in part in peripheral inflammatory pain.