Osmotic stimuli increase brain-derived neurotrophic factor mRNA level in the rat subfornical organ

The effects of water deprivation and chronic salt loading on the expression of the brain-derived neurotrophic factor (BDNF) gene were examined in the rat subfornical organ (SFO), using immunohistochemistry for BDNF and in situ hybridization histochemistry. Increased BDNF-like immunoreactivity was observed in the SFO after water deprivation for 4 days. Water deprivation for 24 h and 2 and 4 days and salt loading for 7 days caused a significant increase in the BDNF gene transcripts in the SFO, compared with euhydrated rats. These results suggest that BDNF in the SFO may be involved in the regulatory mechanisms of body fluid balance.