TIME COURSE OF CHANGES IN GLUTAMATERGIC TRANSMISSION WITHIN NTS DURING CIH EXPOSURE AND THE ROLE OF ΔFOSB

ΔFosB is a transcription factor induced by chronic intermittent hypoxia (CIH), a model of the arterial hypoxemia seen in sleep apnea patients. We reported that 7 days of CIH increases the amplitude of mEPSCs recorded in 2nd order arterial chemoreceptor NTS neurons. We hypothesize that NTS injection of a dominant-negative construct of ΔFosB (provided by Dr. E. Nestler) to block the function of ΔFosB will block the CIH increase in mEPSC. A brain slice preparation was used to record mEPSCs by whole cell patch clamp in a normoxia group and in rats exposed to CIH of differing durations. mEPSC amplitude in normoxia group and after 1, 3, 5, and 7 days CIH exposure averaged 12.3±0.8 pA (n=12), 19.6±1.3 pA (n=11), 17.5±1.6 pA (n=11), 16.7±1.2 pA (n=21), 18.2±0.8 pA (n=7), respectively (all p<.05 vs. normoxia). 1 day after a 7 day exposure, mEPSC amplitude remained increased (17.5±1.6 pA, n=4), after 3 day recovery mEPSC amplitude was similar to normoxia (12.9±1.0 pA, n=7). AAV-GFP-ΔJunD construct was microinjected into NTS to block the function of ΔFosB, then GFP labeled second order NTS neurons were recorded after 1 day and 7 days CIH exposure. ΔFosB inhibition decreased the amplitudes of mEPSCs to normoxia levels in both groups, 13.9±0.6 pA (n=10), 13.0±0.6 pA (n=19), respectively. CIH rapidly enhances the post-synaptic response to glutamatergic synaptic transmission within the NTS and ΔFosB plays a role in mediating this enhancement. ΔFosB is a transcription factor induced by chronic intermittent hypoxia (CIH), a model of the arterial hypoxemia seen in sleep apnea patients. We reported that 7 days of CIH increases the amplitude of mEPSCs recorded in 2nd order arterial chemoreceptor NTS neurons. We hypothesize that NTS injection of a dominant-negative construct of ΔFosB (provided by Dr. E. Nestler) to block the function of ΔFosB will block the CIH increase in mEPSC. A brain slice preparation was used to record mEPSCs from second order NTS neurons by whole cell patch clamp in a normoxia group and in rats exposed to CIH of differing durations. AAV-GFP-ΔJunD construct was microinjected into NTS to block the function of ΔFosB, then GFP labeled second order NTS neurons were recorded after 1 day and 7 days CIH exposure. mEPSC amplitude in normoxia group and after 1, 3, 5, and 7 days CIH exposure averaged 12.3±0.8 pA (n=12), 19.6±1.3 pA (n=11), 17.5±1.6 pA (n=11), 16.7±1.2 pA (n=21), 18.2±0.8 pA (n=7), respectively (all p<.05 vs. normoxia). 1 day after a 7 day exposure, mEPSC amplitude remained increased (17.5±1.6 pA, n=4), after 3 day recovery mEPSC amplitude was similar to normoxia (12.9±1.0 pA, n=7). AAV-GFP-ΔJunD construct was microinjected into NTS to block the function of ΔFosB, then GFP labeled second order NTS neurons were recorded after 1 day and 7 days CIH exposure. ΔFosB inhibition decreased the amplitudes of mEPSCs to normoxia levels in both 1 day and 7 days CIH groups, 13.9±0.6 pA (n=10), 13.0±0.6 pA (n=19), respectively. CIH rapidly enhances the post-synaptic response to glutamatergic synaptic transmission within the NTS and ΔFosB plays a role in mediating this enhancement.