Role of commissural nucleus of solitary tract on the maintenance of hypertension and respiratory activity in renovascular hypertensive rats

      We have demonstrated that renovascular 2-kidney, 1-clip (2K1C) rats presented a higher baseline ventilation and an increased ventilatory response to hypoxia, which suggests peripheral chemoreflex overactivity. In the present study we aimed to evaluate the role of comissural nucleus of solitary tract (cNTS) on the maintenance of hypertension and on diaphragm activity in 2K1C rats. Male Holtzman rats (150-180 g) received a silver clip around the left renal artery to induce renovascular hypertension (n = 6). Rats with sham surgery were used as normotensive control (NT, n = 7). Six weeks after the surgery, saline (NaCl 0.15 M, 60 nl) followed 20 min later by isoguvacine (20 mM; 60 nl – gabaergic agonist), were microinjected into the cNTS of urethane (1.4 g/Kg of body weight; i.v.) anesthetized rats and mean arterial pressure (MAP) and diaphragm activity were recorded before and up to 60 min after isoguvacine. Baseline MAP in 2K1C rats was higher compared to NT rats (193 ± 9, vs. NT: 123 ± 2 mmHg, p < 0.05). Twenty min after isoguvacine injection into the cNTS, there was a greater decrease in MAP in 2K1C rats compared to NT rats (-40 ± 6, vs. NT: -16 ± 3 mmHg, p < 0.05). Isoguvacine in the cNTS also induced a decrease in diaphragm activity in 2K1C animals (Δ -19 ± 6 vs. NT: 1 ± 7 %, 60 min; p < 0.05). These data showed that cNTS is important to maintain the hypertension and diaphragm activity in 2K1C rats. Support: CAPES, FAPESP/PRONEX, CNPq, PROPE
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