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The effects of cholinoceptor agonists and antagonists on C‐fibre evoked responses in the substantia gelatinosa of neonatal rat spinal cord slices
Author(s) -
Bleazard L.,
Morris R.
Publication year - 1993
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1993.tb13921.x
Subject(s) - spinal cord , neuroscience , nociception , chemistry , medicine , anesthesia , biology , receptor
1 The effects of cholinoceptor agonists and antagonists were studied on neurones in the substantia gelatinosa (SG) of an in vitro spinal cord slice and nerve preparation from neonatal rats. 2 Bath application of carbachol (1–50 μ m ) reduced, in a dose‐related manner, the amplitude and duration of the excitatory postsynaptic potentials (e.p.s.ps) evoked in response to nerve stimulation. 3 The latencies and stimulation thresholds required to evoke these e.p.s.ps suggested that the majority were due to C‐fibre activation. 4 The reduction in e.p.s.p. amplitude and duration produced by carbachol was reversed by the muscarinic antagonists, atropine (in 8 out of 11 cells), pirenzepine (in 7 out of 9 cells) and methoctramine (in 8 out of 9 cells) and by the nicotinic antagonist mecamylamine (in 3 out of 7 cells). 5 Injection of small hyperpolarizing or depolarizing pulses was associated with no change in conductance in 19 out of 26 (73%) of cells tested, suggesting that an action at a site presynaptic to the neurone studied could account for part of the effect of carbachol. 6 It is proposed that some of the cholinoceptors associated with the e.p.s.p. depression are located on C‐fibres.