PMID- 9503338
OWN - NLM
STAT- MEDLINE
DCOM- 19980429
LR  - 20190512
IS  - 0022-3751 (Print)
IS  - 1469-7793 (Electronic)
IS  - 0022-3751 (Linking)
VI  - 506 ( Pt 3)
IP  - Pt 3
DP  - 1998 Feb 1
TI  - Inhibitory control of plateau properties in dorsal horn neurones in the turtle 
      spinal cord in vitro.
PG  - 795-808
AB  - 1. The role of inhibition in control of plateau-generating neurones in the dorsal 
      horn was studied in an in vitro preparation of the spinal cord of the turtle. 
      Ionotropic and metabotropic inhibition was found to condition the expression of 
      plateau potentials. 2. Blockade of gamma-aminobutyric acid (GABAA) and glycine 
      receptors by their selective antagonists bicuculline (10-50 microM) and 
      strychnine (5-20 microM) enhanced the excitatory response to stimulation of the 
      dorsal root and facilitated the expression of plateau potentials. 3. Bicuculline 
      and strychnine also facilitated the generation of plateau potentials in response 
      to depolarizing current pulses, suggesting the presence of tonic ionotropic 
      inhibitory mechanisms in turtle spinal cord slices. 4. Activation of GABAB 
      receptors also inhibited plateau-generating neurones. The selective agonist 
      baclofen (5-50 microM) inhibited wind-up of the response to repeated 
      depolarizations induced synaptically or by intracellular current pulses. 5. 
      Baclofen reduced afferent synaptic input. This effect was not affected by 
      bicuculline or strychnine and was blocked by the selective GABAB receptor 
      antagonist 2-hydroxysaclofen (2-OH-saclofen, 100-400 microM). 6. 
      Postsynaptically, baclofen inhibited plateau properties. Activation of GABAB 
      receptors produced a hyperpolarization (7.0 +/- 0.5 mV, mean +/- S.E.M., n = 29) 
      with an associated decrease in input resistance (22.7 +/- 3.1%, n = 24). These 
      effects were blocked by extracellular Ba2+ (1-2 mM). 7. When the baclofen-induced 
      hyperpolarization and shunt were compensated for by adjusting the bias current 
      and the strength of the stimulus, baclofen still inhibited generation of plateau 
      potentials. Wind-up and after-discharges were also inhibited by baclofen. These 
      effects remained in the presence of tetrodotoxin (1 microM) and were antagonized 
      by 2-OH-saclofen. 8. The inhibition of plateau properties was observed even when 
      the baclofen-induced hyperpolarization and shunt were blocked by Ba2+ and when 
      potassium channels were blocked by Ba2+ (3 mM), tetraethylammonium (TEA, 15 mM) 
      and apamin (0.25-0.5 microM). The baclofen-sensitive component of the plateau 
      potential was reduced by nifedipine (10 microM), suggesting a modulation of 
      postsynaptic L-type Ca2+ channels. 9. We suggest that inhibitory regulation of 
      plateau properties plays a role in somatosensory processing in the dorsal horn. 
      The inhibitory control of wind-up and after-discharges may be particularly 
      significant in physiological and therapeutic control of central sensitization to 
      pain.
FAU - Russo, R E
AU  - Russo RE
AD  - Department of Medical Physiology, Panum Institute, University of Copenhagen, 
      Denmark. rrusso@iibee.edu.uy
FAU - Nagy, F
AU  - Nagy F
FAU - Hounsgaard, J
AU  - Hounsgaard J
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - J Physiol
JT  - The Journal of physiology
JID - 0266262
RN  - 0 (GABA Agonists)
RN  - 0 (GABA Antagonists)
RN  - 0 (Glycine Agents)
RN  - 0 (Receptors, GABA-A)
RN  - 0 (Receptors, Glycine)
RN  - 0 (Receptors, Metabotropic Glutamate)
SB  - IM
MH  - Animals
MH  - Electric Stimulation
MH  - Electrophysiology
MH  - Excitatory Postsynaptic Potentials/drug effects
MH  - GABA Agonists/pharmacology
MH  - GABA Antagonists/pharmacology
MH  - Glycine Agents/pharmacology
MH  - In Vitro Techniques
MH  - Membrane Potentials/physiology
MH  - Neurons/metabolism/physiology
MH  - Nociceptors/drug effects
MH  - Patch-Clamp Techniques
MH  - Receptors, GABA-A/metabolism
MH  - Receptors, Glycine/metabolism
MH  - Receptors, Metabotropic Glutamate/drug effects
MH  - Spinal Cord/cytology/*physiology
MH  - Turtles/*physiology
PMC - PMC2230747
EDAT- 1998/03/21 00:00
MHDA- 1998/03/21 00:01
PMCR- 1999/02/01
CRDT- 1998/03/21 00:00
PHST- 1998/03/21 00:00 [pubmed]
PHST- 1998/03/21 00:01 [medline]
PHST- 1998/03/21 00:00 [entrez]
PHST- 1999/02/01 00:00 [pmc-release]
AID - 10.1111/j.1469-7793.1998.795bv.x [doi]
PST - ppublish
SO  - J Physiol. 1998 Feb 1;506 ( Pt 3)(Pt 3):795-808. doi: 
      10.1111/j.1469-7793.1998.795bv.x.