Pre‐treatment with hydrogen peroxide affects water intake and anti‐diuresis to cholinergic activation of the medial septal area

Abstract

Previous studies demonstrated that hydrogen peroxide (H2O2) injected intracerebroventricularly (icv) reduces the pressor response induced by icv angiotensin II or the cholinergic agonist carbachol (CARB). In the present study we investigated the effects of H2O2 injected into the medial septal area (MSA) on water intake, natriuresis, caliuresis and anti-diuresis to CARB also injected into the MSA. Male Holtzman rats (280–320 g, N = 6–9) with stainless steel cannulas implanted into the MSA were used. Phosphate buffered saline (PBS) or H2O2 (5 μmol/0.5 μL) was injected into the MSA 1 min before CARB (4 nmol/0.5 μL) or saline into the same area. Urine excretion was tested for 2 h after intragastric water load (10% of body wt.). Injection of H2O2 into the MSA reduced CARB-induced water intake (8 ± 2.0, vs. PBS + CARB: 16.6 ± 1.9 mL/1 h, p<0.05). CARB into the MSA also induced anti-diuresis (7.7 ± 0.7, vs. saline + PBS: 9.6 ± 0.9 ml/2 h, p<0.05) that was reversed by H2O2 into the MSA (10.1 ± 1.2 ml/2 h), whereas H2O2 alone into the MSA increased the diuresis (12.1 ± 1.0 mL/2 h). The pre-treatment with H2O2 into the MSA did not change CARB-induced natriuresis and caliuresis. The results suggest that H2O2 in the MSA inhibits the dipsogenic and anti-diuretic mechanisms activated by cholinergic stimulation of the MSA. Support: FAPESP, CNPq, CNPq-PIBIC.