Plateau potentials and membrane oscillations in parasympathetic preganglionic neurones and intermediolateral neurones in the rat lumbosacral spinal cord.
The Journal of Physiology. 2005-02-21; 563(2): 583-596
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1. J Physiol. 2005 Mar 1;563(Pt 2):583-96. Epub 2004 Dec 23.
Plateau potentials and membrane oscillations in parasympathetic preganglionic
neurones and intermediolateral neurones in the rat lumbosacral spinal cord.
Derjean D(1), Bertrand S, Nagy F, Shefchyk SJ.
(1)Spinal Cord Research Centre, Department of Physiology, University of Manitoba,
Winnipeg, Manitoba, Canada R3E 3J7.
Whole-cell patch recordings were made from parasympathetic preganglionic neurones
(P-PGNs) and unidentified intermediolateral (IML) neurones in thick slices of the
lower lumbar and sacral spinal cord of 14- to 21-day-old rats. The P-PGNs and IML
neurones examined were similar in terms of soma sizes, input resistance and
capacitance, and displayed a sag conductance as well as rebound firing. In the
absence of drugs, the neurones responded with either tonic or adapting firing to
depolarizing current steps. However, in the presence of the group I metabotropic
glutamate receptor agonist (RS)-3,5-dihydroxyphenylglycine (DHPG), almost half of
the neurones displayed accelerating firing rates during the constant current
injection, followed by a sustained after-discharge. In the presence of TTX,
plateau potentials were observed. The firing changes and plateaux were blocked by
nifedipine, an L-type Ca2+ channel blocker, and (S)-(-)-Bay K8644 was able to
produce these firing changes and plateaux in the absence of DHPG, demonstrating
the involvement of an L-type Ca2+ conductance. Ca2+-activated nonspecific
cationic conductances also appear to contribute to the firing changes. A few
neurones displayed membrane oscillations and burst firing in the presence of
DHPG. The results suggest that the firing characteristics of both P-PGNs and
other neurones likely to be involved in caudal spinal reflex control are not
static but, rather, quite dynamic and under metabotropic glutamate receptor
modulatory control. Such changes in firing patterns may be involved in normal
pelvic parasympathetic reflex function during micturition, defaecation and sexual
reflexes, and may contribute to the abnormal output patterns seen with loss of
descending brainstem input and visceral or perineal sensory disturbances.
PMID: 15618277 [Indexed for MEDLINE]