Postnatal development of [3H]flunitrazepam and [3H]strychnine binding sites in rat spinal cord localized by quantitative autoradiography

Abstract The development of inhibitory receptors in rat spinal cord was investigated by autoradiography using [ 3 H]flunitrazepam as a ligand for benzodiazepine receptors and [ 3 H]strychnine as a ligand for glycine receptors. The development of benzodiazepine receptors follows a similar pattern at all levels of the spinal cord. The density of [ 3 H]flunitrazepam binding sites is already high at birth, increases 2-fold by days 3–7 and thereafter declines to levels already present at birth. In contrast, [ 3 H]strychnine binding sites are weakly expressed at birth and increase up to 7-fold between days 4 and 21. A craniocaudal gradient in the development of glycine receptors is not apparent. However, maturation of [ 3 H]strychnine binding in the ventral horn precedes that in the dorsal horn for 3–4 days. In summary, the developmental expression of these two inhibitory receptors in the spinal cord appears to be regulated differently.