Spike activity of neurons in the lateral hypothalamus in rats during microiontophoretic application of melatonin and noradrenaline.

Microiontophoretic application of melatonin to the perineuronal space of nerve cells in the lateral hypothalamus of WAG and Fischer-344 rats led to decreases in the frequency and regularization of the spike activity of neurons, and also blocked activation of neurons and changing the patterns of adrenaline-induced spike activity. The effects of melatonin were more marked in WAG rats, which demonstrated the more active behavior in the open field test and were predicted to be more resistant to emotional stress, than in passive Fischer-344 rats, with predisposition to emotional stress. These results suggest that the mechanism of the stress-protective action of melatonin involves suppression of the spike activity of neurons in emotiogenic brain structures and changes in their sensitivity to noradrenaline.