PONTINE NEURONS ARE ELEMENTS OF THE NETWORK RESPONSIBLE FOR THE 10-HZRHYTHM IN SYMPATHETIC-NERVE DISCHARGE

The current study was designed to test the hypothesis that pontine neu rons are elements of the network responsible for the 10-Hz rhythm in s ympathetic nerve discharge (SND). The first series of experiments test ed whether chemical inactivation of neurons in the rostral dorsolatera l pens (RDLP) or caudal ventrolateral pens (CVLP) affected inferior ca rdiac postganglionic SND of urethan-anesthetized cats. Muscimol microi njections into either region eliminated the 10-Hz rhythm in SND, suppo rting the view that pontine neurons are involved in the expression of this rhythm. Additional experiments were designed to determine if pont ine neurons have activity correlated to the 10-Hz rhythm in SND or whe ther they merely provide a tonic (nonrhythmic) driving input to the rh ythm generator. Coherence analysis revealed that local field potential s recorded from the RDLP or CVLP had a 10-Hz component that was signif icantly correlated to SND. Also, spike-triggered averaging and coheren ce analysis showed that the naturally occurring discharges of individu al RDLP or CVLP neurons were correlated to the 10-Hz rhythm in SND. Ta ken together, these data support the hypothesis that RDLP and CVLP neu rons are essential for the expression of the 10-Hz rhythm in SND and t hat they are elements of or receive input from the rhythm generator.