Neurons of the rostral ventrolateral medulla mediate somatic pressor reflex

Stornetta RL, Morrison SF, Ruggiero DA, Reis DJ.

Department of Neurology, Cornell University Medical College, New York, New York 10021

This article was investigating whether rostral ventral lateral is mediating the somatic pressor reflex. The somatic pressor reflex is activated when the sciatic nerve for example is stimulated, this will cause an increase in arterial pressure along with SNA. The SPR had been identified in cats and dogs however not in rats, so they investigated this response in rats. Where the information from the stimulation travel up afferent nerve was been integrated into a response that would cause changes in Arterial Pressure (AP) was unknown. Since they knew that RVLM neurons played role in tonically and in reflex control of blood pressure along with the fact that the neurons in RVLM had an excitatory effect on sympathetic preganglionic neuron in the IML, this lead them to believe that the SPR may be mediated by the RVLM. So what the concluded from the study was the following:

1.       Stimulation of the sciatic, sural and saphenous caused increases in AP and HR  which is similar dog and cat

2.       Stimulation of muscle nerves such as tibial or femoral nerves resulted in decreases in AP and HR.

3.       After transection of the anterior pons the SPR was still functioning suggesting that the SPR is controlled by a brain region of somewhere below the pons

4.       Lesions of the LRN  reduced the SPR but when kainic(before lesion) was injected into the LRN the SPR was still functional meaning that when the LRN was not the brain region mediating this responses but when the area was lesion there may have been nerve fibers destroyed or because LRN is so close to RVLM some of the neurons in this area could have been damaged

5.       Finally they found that if there is unilateral lesion of an RVLM and the contralateral sciatic is stimulated then the response will be blocked.