Lesions of the ventrolateral medulla in normal and vasopressin-deficient (Brattleboro) rats

The cardiovascular response to electrolytic lesions of the A1 noradrenaline cell group (A1 lesion) were studied in the rat. A1 lesions in normal rats cause acute hypertension and bradycardia and elevate plasma arginine-vasopressin (AVP), as previously described in the rabbit. After A1 lesions in vasopressin deficient rats the hypertension is not reduced compared to that seen in normal rats, but the bradycardia is attenuated. AVP makes a greater contribution to the bradycardia than to the hypertension after A1 lesions.