Spinal segments communicating resting sympathetic activity to postganglionic nerves of the stellate ganglion

Abstract

It has been shown earlier using sympathetic reflexes and anatomic techniques that preganglionic neurons controlling different effectors occupy wide and overlapping ranges of adjacent segments in the spinal cord (cardiac: T1–T7, vertebral: T2–T8). Because, however, the majority of preganglionic neurons are silent at resting states, the present study was designed to estimate the segmental map of subsets of these neurons including only those active at rest using simultaneous recordings from the inferior cardiac and vertebral nerves, under chloralose-urethan or urethan anesthesia. In 22 cats, thoracic white rami T1–T8 were cut in a sequential manner. Three-minute-long data segments were recorded between sectionings and analyzed in the frequency domain using the fast Fourier transform. We found that cardiac and vertebral active maps involved segments T3–T5 and T4–T8, respectively. In individual experiments, however, most of the power of rhythmic activity originated from only one or two segments and the dominant segments for the two nerves never overlapped. Moreover, the separation between dominant segments generating cardiac and vertebral nerve discharges was wider and the distribution of tonically active preganglionic neurons projecting to each nerve was narrower under urethan than chloralose-urethan anesthesia. We conclude that the proportion of active to quiescent preganglionic neurons regulating cardiac and vertebral nerve discharges varies from spinal segment to segment and that active neurons projecting to these nerves are nonoverlapping.

Low-Frequency Oscillations in Cardiac Sympathetic Neuronal Activity

“…Experiments conducted in conscious and anesthetized cats with either intact or denervated baroreceptors have been the model of choice to study periodic oscillations in CSNA. However, the frequency of rhythmic neuronal oscillations reported so far appears to be dominated by cardiac-related rhythms in the 2-to 6-Hz range (Ninomiya et al, 1989(Ninomiya et al, , 1990(Ninomiya et al, , 1993Kocsis et al, 1990;Hedman et al, 1994;Kocsis, 1994;Hedman and Ninomiya, 1995;Kocsis and Gyimesi-Pelczer, 1998;Larsen et al, 2000) or by respiratory-related rhythms in synchrony with the discharge frequency of the phrenic nerve (Kollai and Koizumi, 1980). The presence of LF oscillations in cardiac postganglionic fibers has not been documented yet, which appears to be counterintuitive, since the final synaptic relay in the neurocardiac axis would be expected to follow the same oscillatory pattern generated by either bulbar presympathetic or spinal preganglionic neuronal networks.…”

“…This allows sampling of the neural signal once per-heart beat and application of autoregressive modeling analysis of sympathetic nerve discharges and R-R interval duration (Lombardi et al, 1990;Montano et al, 1992Montano et al, , 2000. In contrast, the studies assessing cardiac postganglionic nerve discharges cited above did not take measurements to eliminate cardiac-related synchronous activity which may have prevented the detection of LF oscillations (Kocsis et al, 1990;Kocsis, 1994;Kocsis and Gyimesi-Pelczer, 1998;Larsen et al, 2000).…”

Delta-range coupling between prefrontal cortex and hippocampus supported by respiratory rhythmic input from the olfactory bulb in freely behaving rats

“…We found major differences between RRO in sleep and under urethane anesthesia which raise important questions about the traditional use of the latter for modeling oscillatory networks in sleep 7,52,64 . It is known that different types of brain oscillations better survive urethane anesthesia [65][66][67][68] , compared with many other anesthetics. It is especially compelling that HC theta rhythm appears spontaneously in this preparation, alternating with non-theta states, and can also be elicited by brainstem stimulation thus offering a viable model for mechanistic investigations of generating this rhythm and related neuropharmacology [69][70][71] .…”

Respiratory coupling between prefrontal cortex and hippocampus of rats anesthetized with urethane in theta and non-theta states

“…sniffing. Importantly, different types of brain oscillations were shown to survive anesthesia with urethane better than with other anesthetics [11][12][13][14][15][16][17] .…”