Sf. Deplazas et Mc. Gravielle, PRESENCE OF ENDOGENOUS INHIBITORS OF BENZODIAZEPINE BINDING IN DEVELOPING CHICK OPTIC LOBE, NeuroReport, 5(15), 1994, pp. 1957-1959
AN endogenous inhibitor of benzodiazepine receptor binding was removed
from synaptic membranes of developing chick optic lobe by an exhausti
ve buffer washing procedure. This treatment increased [H-3]flunitrazep
am binding at all stages of development, although this effect was grea
ter at early stages (embryonic day 14-16). Scatchard analysis performe
d on exhaustively washed membranes at embryonic day 16 and postnatal d
ay 15 revealed the presence of a single population of flunitrazepam bi
nding sites with apparent dissociation constants (K-d) of 1.99 +/- 0.1
1 and 3.28 +/- 0.10 nM and a maximal number of binding sites (B-max) o
f 1.07 +/- 0.08 and 1.22 +/- 0.11 pmol mg(-1) protein, respectively. A
t both stages of development, the addition of inhibitory material, pre
sent in the supernatants obtained after the washing procedure, reduced
the affinity of recognition sites for [H-3]flunitrazepam with K-d of
4.92 +/- 0.13 and 5.62 +/- 0.12 nM, respectively while their B-max val
ues remained unchanged. These studies demonstrate the presence of an e
ndogenous material in developing chick optic lobe which competitively
inhibits [H-3]flunitrazepam binding to its receptor site.