[Role of ventrolateral medulla in pressor response elicited by stimulation of abdominal vagi in cats].

The experiments were performed on 51 cats of either sex weighing 1.8-2.4 kg to investigate the role of the ventrolateral medulla in the pressor response elicited by stimulation of central ends of abdominal vagi. We observed that both the stimulation of the central ends of abdominal vagi and occlusion of one carotid artery increased the blood pressure by 17.4 +/- 1.6 mmHg (n = 51, P less than 0.01) and 14.7 +/- 1.9 mmHg (n = 19, P less than 0.01) respectively; blockade of the caudal ventrolateral medulla or trapezoid bodies with lidocaine had little effect on blood pressure and the pressor response, but blockade of the rostral ventrolateral medulla with either lidocaine or kainic acid could cause profound depression, and even abolition, of the pressor response. Moreover, application of atropine and phentolamine to the RVL severely inhibited the abdominal vagal pressor response without affecting the baroreceptor reflex. Taken together, we conclude that the RVL is a very important relay in the pathway of the abdominal vagal pressor response in which the adrenergic and cholinergic mechanisms may be involved in the RVL, and it seems that the pressor response pathway is independent of that of the baroreceptor reflex in the RVL.