Effects of cervical vagus nerve stimulation on amygdala-evoked responses of the medial prefrontal cortex neurons in rat

In experiments on urethane-anaesthetized rats, the effects of repetitive vagus nerve stimulation (VNS) on responses of medial prefrontal cortex (mPFC) neurons to electrical stimulation of the basal nucleus of the amygdala were examined before and after intracerebroventricular administration of the neuronal nitric oxide synthase inhibitor 7-nitroindasole (7-NI). It was shown that the amygdala-evoked responses of cortical neurons were inhibited by repetitive VNS (pulses 50-150 μA, 0.5 ms, frequency 10 Hz). 7-NI administration did not change the amygdala-evoked neuronal reactions but reversed the effect of VNS on them. The present results suggest that the inhibitory action of VNS on amygdala-mPFC neurotransmission may involve a cortical NO-dependent mechanism.