Presence of endogenous inhibitors of benzodiazepine binding in developing chick optic lobe

FISZER DE PLAZAS, SARA; MARIA CLARA GRAVIELLE

NEUROREPORT

Lippincott Williams & Wilkins

Año: 1994 vol. 5 p. 1957 - 1959

0959-4965

An endogenous inhibitor of benzodiazepine receptor binding was removed from synaptic membranes of developing chick optic lobe by an exhaustive buffer washing procedure. This treatment increased [3.H]flunitrazepam binding at all stages of development, although this effect was greater at early stages (embryonic day 14-16). Scatchard analysis performed on exhaustively washed membranes at embryonic day 16 and postnatal day 15 revealed the presence of a single population of flunitrazepam binding sites with apparent dissociation constants (Kd) of 1.99 +/- 0.11 and 3.28 +/- 0.10 nM and a maximal number of binding sites (Bmax) of 1.07 +/- 0.08 and 1.22 +/- 0.11 pmol mg-1 protein, respectively. At both stages of development, the addition of inhibitory material, present in the supernatants obtained after the washing procedure, reduced the affinity of recognition sites for [3H]flunitrazepam with Kd of 4.92 +/- 0.13 and 5.62 +/- 0.12 nM, respectively while their Bmax values remained unchanged. These studies demonstrate the presence of an endogenous material in developing chick optic lobe which competitively inhibits [3H]flunitrazepam binding to its receptor site.