SPONTANEOUS ACTIVITY AND BAROSENSITIVITY OF THE BAROSENSITIVE NEURONSIN THE ROSTRAL VENTROLATERAL MEDULLA OF HYPERTENSIVE RATS INDUCED BY TRANSECTION OF AORTIC DEPRESSOR NERVES

In order to determine the role of the rostral ventrolateral medulla (R VLM) in the development of neurogenic hypertension, the aortic depress or nerves of rats were transected (tADN) to produce neurogenic hyperte nsion. The rate and pattern of firing of the barosensitive RVLM neuron s of the treated rats were studied. In neurogenic hypertensive rats, t he RVLM barosensitive neurons exhibited a faster firing rate and a sho rter interspike interval (ISI) than the corresponding values of the co ntrol and sham groups, indicating an enhanced spontaneous activity of these neurons in the hypertensive rats. The coefficient of variation ( cv) and skewness (sk) of the ISI histogram, parameters reflecting the regularity of neuronal firing, were smaller in neurogenic hypertensive than in the control and sham-operated rats. Following tADN, the respo nsiveness of these neurons to blood pressure changes was attenuated, s uggesting a reduced intrinsic barosensitivity of neurons and/or a redu ced baroreceptor input. The increase in spontaneous activity and firin g regularity of RVLM barosensitive neurons imply an enhancement in the efficacy of outflow from these neurons. The increased efficacy of the outflow from the RVLM barosensitive neurons and the resetting of the baroreflex may contribute to the genesis of neurogenic hypertension. ( C) 1998 Elsevier Science B.V. All rights reserved.