Expression of c-fos in brain subcortical structures in response to nauseant lithium chloride and osmotic pressure in rats.

Immunohistochemistry was used to map c-fos expression in rats to investigate the neural substrates that mediate the emetic action of lithium chloride and the effect of osmotic pressure. Solutions of 3% lithium chloride or 4.14% saline, isotonic to each other, as well as 0.65% lithium chloride or 0.9% saline, also isotonic to each other, were administered intraperitoneally (3 ml/kg) in rats. Both lithium chloride and osmotic pressure enhanced c-fos expression in the nuclei of the solitary tract, the paraventricular nuclei and supraoptic nuclei of the hypothalamus, and in the amygdala. This suggests that these brain structures might be the sites where the autonomic, neuroendocrine and behavioral responses elicited by lithium chloride and osmotic pressure are integrated.