Chronic vagal stimulation decreased vasopressin secretion and sodium ingestion in heart failure rats after myocardial infarction.

Chronic vagal stimulation (VS) markedly improved long-term survival in the heart failure rats. We examined the effects of VS on arginine vasopressin (AVP) secretion and salt ingestion in heart failure rats after myocardial infarction (MI). Surviving rats after MI were randomly assigned to two groups. One group was treated with sham stimulation (SS), and the other group was treated with VS. All rats could access water and 1.8% NaCl solution ad libitum. Treatment started at 2 weeks after MI, and continued for 6 weeks. We monitored drinking behavior during treatment. At the end of treatment, we measured hemodynamics and plasma levels of AVP and brain natriuretic peptide (BNP). The plasma AVP and BNP levels were significantly lower in the VS group than the SS group. VS significantly inhibited the ingestion of 1.8% NaCl solution. The normalized biventricular weight of the VS group was significantly lower than that of the SS group. The VS group had significantly lower left ventricular end-diastolic pressure, and higher cardiac index than the SS group. In conclusion, these results suggest that chronic VS regulates the water balance by suppression of plasma AVP level and salt ingestion in the heart failure rats after MI.