Role of ventrolateral medulla in generating the 10-Hz rhythm in sympathetic nerve discharge.

Barman SM, Gebber GL. Am J Physiol Regul Integr Comp Physiol. 2007 Jul;293(1):R223-33 I'm kind of new to the details of the 10Hz rhythm. It's seen in sympathetic nerves and when it becomes apparent, it is linked with an increase in arterial pressure. It seems to be always somewhat in effect, but it's most noticeable after barorecepter denervation. Generation of the 10Hz rhythm seems to originate in the brainstem, since decerebration doesn't stop it, but spinal transection does. The activity of individual brainstem neurons in RVLM, CVLM, and medullary raphe is correlated with 10hz. This is somewhat strange because CVLM neurons do not have spinal projections, but they're still correlated with this 10Hz activity. They wanted to look at how these different regions interact, so they used microinection of drugs in to these regions to figure out the microcircuitry involved. What they found is that inection of GABAergic antagonists in to the VLM (rostral OR caudal) could eliminate the 10Hz signal, even with only unilateral injections. Strangely, glutamatergic antagonists could reduce the 10Hz too. They think this comes down to a network of GABAergic interneurons in the CVLM and the RVLM communicating with the neurons that we generally think of when we think of those regions. This should make Max happy, since he's pretty excited about interneurons. -DH