Elsevier

Neuroscience

Volume 170, Issue 3, 27 October 2010, Pages 827-838
Neuroscience

Cognitive, Behavioral, and Systems Neuroscience
Research Paper
Spontaneous rhythmogenic capabilities of sympathetic neuronal assemblies in the rat spinal cord slice

https://doi.org/10.1016/j.neuroscience.2010.07.007Get rights and content
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Abstract

Neuronal networks generating rhythmic activity as an emergent property are common throughout the nervous system. Some are responsible for rhythmic behaviours, as is the case for the spinal cord locomotor networks; however, for others the function is more subtle and usually involves information processing and/or transfer. An example of the latter is sympathetic nerve activity, which is synchronized into rhythmic bursts in vivo. This arrangement is postulated to offer improved control of target organ responses compared to tonic nerve activity. Traditionally, oscillogenic circuits in the brainstem are credited with generating these rhythms, despite evidence for the persistence of some frequencies in spinalized preparations. Here, we show that rhythmic population activity can be recorded from the intermediolateral cell column (IML) of thoracic spinal cord slices. Recorded in slices from 10- to 12-day-old rats, this activity was manifest as 8–22 Hz oscillations in the field potential and was spatially restricted to the IML. Oscillations often occurred spontaneously, but could also be induced by application of 5-HT, α-methyl 5-HT or MK212. These agents also significantly increased the strength of spontaneous oscillations. Rhythmic activity was abolished by TTX and attenuated by application of gap junction blockers or by antagonists of GABAA receptors. Together these data indicate that this rhythm is an emergent feature of a population of spinal neurons coupled by gap junctions. This work questions the assumption that sympathetic rhythms are dependent on supraspinal pacemaker circuits, by highlighting a surprisingly strong rhythmogenic capability of the reduced sympathetic networks of the spinal cord slice.

Key words

oscillation
sympathetic nervous system
serotonin
spontaneous activity
gap junctions
GABA

Abbreviations

aCSF
artificial cerebrospinal fluid
Cx36
connexin 36
GABA
gamma amino butyric acid
Hb9
homeobox gene 9
HERG
human Ether-a-go-go Related Gene
mRNA
messenger RNA
IML
intermediolateral cell column
IQ
interquartile
SEM
standard error of the mean
SPNs
sympathetic preganglionic neurons

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1

Present address: Institute of Neuroscience, Newcastle University Medical School, Framlington Place, Newcastle-upon-Tyne, NE2 4HH, UK.