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The location of GABA B receptor binding sites in mammalian spinal cord
Author(s) -
Price G. W.,
Kelly J. S.,
Bowery N. G.
Publication year - 1987
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.890010605
Subject(s) - rhizotomy , spinal cord , lamina , gabab receptor , neurotensin , anatomy , chemistry , nociception , anesthesia , biology , receptor , neuropeptide , neuroscience , medicine , agonist , biochemistry
GABA B binding sites in rat spinal cord have been detected by receptor autoradiography using 3 H‐GABA in the presence of isoguvacine. The sites could be demonstrated throughout the spinal cord grey matter. The maximum concentration of GABA B sites occurred in lamina II with substantial amounts in other laminae of the dorsal horn. Much lower levels were detected in the ventral horn. Unilateral rhizotomy reduced the number of GABA B sites in the dorsal horn without affecting levels in the ventral horn. The greatest reduction occurred in lamina II with 18% loss 2 days after surgery, 23% after 4 days, 25% after 6 days, and 48% after 15 days. The change after 15 days was comparable to that produced 4 months after neonatal capsaicin administration (50 mg/kg). The only apparent difference between rhizotomy and capsaicin treatment occurred in lamina IV, where rhizotomy produced a greater reduction than capsaicin. 3 H‐Neurotensin binding in sections from the same animals was unaltered after rhizotomy, indicating a lack of change in the populations of neurons containing neurotensinbinding sites. This would support the view that up to 50% of GABA B binding sites are located on nerve terminals. The greater reduction in lamina IV after rhizotomy would suggest that GABA B sites may be present on large‐diameter afferent fibres that terminate in this region as well as on smaller‐diameter C and A δ fibres.