Autoradiographic localization of [H-3]thiocolchicoside binding sites in the rat brain and spinal cord

W. Balduini et al., Autoradiographic localization of [H-3]thiocolchicoside binding sites in the rat brain and spinal cord, NEUROPHARM, 40(8), 2001, pp. 1044-1049
Citations number
Categorie Soggetti
Neurosciences & Behavoir
Journal title
ISSN journal
0028-3908 → ACNP
Year of publication
1044 - 1049
SICI code
Thiocolchicoside is used in humans as a myorelaxant drug with anti-inflamma tory and analgesic activity. Recently we established the experimental condi tions that allowed the identification of [H-3]thiocolchicoside binding site s in synaptic membranes of rat spinal cord and cerebral cortex. The pharmac ological characterization of these sites indicated that GABA and several of its agonists and antagonists, as well as strychnine, were able to interact with [H-3]thiocolchicoside binding in a dose-dependent manner and with dif ferent affinities. In order to gain more insight into the nature and the an atomical distribution of the binding sites labeled by [H-3]thiocolchicoside . in the present study we examined the localization of these sites on paras agittal and coronal sections of the rat brain and spinal cord, respectively , using receptor autoradiography. In the spinal cord an intense signal was observed in the gray matter, with the highest density occurring in the supe rficial layers of the dorsal horns. Strychnine completely displaced [H-3] t hiocolchicoside binding, whereas GABA only partially removed the radioligan d from its binding sites. In the brain, specific binding occurred in severa l areas and was displaced by both GABA and strychnine. The distribution of [H-3]thiocolchicoside binding sites in brain sections, however, did not mat ch that found for [H-3]muscimol. Furthermore, cold thiocolchicoside was not able to completely displace [H-3]muscimol binding, and showed a different efficacy in the various areas labeled by the radioligand. We conclude that thiocolchicoside may interact with a subpopulation of GABA, receptors havin g low-affinity binding sites for GABA, Furthermore, the observed sensitivit y to strychnine in the spinal cord indicates an interaction also with stryc hnine-sensitive glycine receptors, suggesting that the pharmacological effe cts of thiocolchicoside may be the result of its interaction with different receptor populations. (C) 2001 Elsevier Science Ltd. All rights reserved.