Pregnancy increases sympathetic nerve activity: role of the arcuate nucleus (1171.5)

Normal pregnancy increases sympathetic nerve activity (SNA), which is further elevated in hypertensive disorders like preeclampsia. However, the mechanisms are unknown. The arcuate nucleus (ArcN), recently identified as a regulator of SNA, undergoes profound changes during pregnancy and other reproductive states. Therefore, we tested the hypothesis that the ArcN contributes to the elevated SNA during pregnancy, by determining if inhibition of the ArcN with the GABA A agonist, muscimol (30 pmol in 30 nL), decreases SNA and mean arterial pressure (MAP) more in late pregnant (P) compared to nonpregnant (NP) SD α‐chloralose anesthetized rats. Compared to NP rats, P rats exhibited lower MAP (P: 83±3 mmHg, n=12; NP: 111±4 mmHg, n=13; P<0.05), higher HR (P: 420±8 bpm, n=12; NP: 367±12 bpm, n=13; P<0.05), elevated lumbar SNA (LSNA; P: 1.9±0.2 µV, n=4; NP: 0.6±0.2 µV, n=4; P<0.05) and elevated splanchnic SNA (SSNA; P: 3.5±0.7 µV, n=4; NP: 0.9±0.2 µV, n=5; P<0.05); renal SNA (RSNA) was not significantly different between groups (P: 5.3±1.7, n=4; NP: 4.2±0.9 µV, n=4). In pregnant rats, ArcN nanoinjection of muscimol significantly decreased (P<0.05) MAP (‐13.3±1.6 mmHg), HR (‐14.5±1.6 bpm), LSNA (‐14.9±3.1% control), SSNA (‐14.4±1.8 % control), and RSNA (‐12.6±0.6 % control). ArcN muscimol did not significantly alter these variables in NP rats. In conclusion, these data suggest that, during pregnancy, the ArcN contributes to sustained increases in sympathetic tone to multiple organs. Grant Funding Source : Supported by HL088552 and AHA.