The binding of [H-3]flunitrazepam, [H-3]Ro 5-4864, and [H-3]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [H-3]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [H-3]Ro 5-4864 and [H-3]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (K(D) values of 24 +/- 2.3 and 2.2 +/- 0.8 nM, and B(max) values of 440 +/- 35 and 1,482 +/- 110 fmol/mg of protein, respectively). The binding was temperature- and protein-dependent. Displacement studies showed a similar rank order of potency of various unlabeled ligands against both [H-3]Ro 5-4864 and [H-3]PK 11195 (PK 11195 > Ro 5-4864 > flunitrazepam > flumazenil). These results suggest that peripheral-type benzodiazepine receptors are present in the retina of the rabbit, but not of the turtle.
THE PERIPHERAL-TYPE BENZODIAZEPINE RECEPTOR LIGANDS [H-3] RO-5-4864 AND [H-3] PK-11195 BIND TO THE RETINA OF RABBIT, BUT NOT OF TURTLE
GIANNACCINI, GINO;MARTINI, CLAUDIA;LUCACCHINI, ANTONIO;
1993-01-01
Abstract
The binding of [H-3]flunitrazepam, [H-3]Ro 5-4864, and [H-3]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [H-3]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [H-3]Ro 5-4864 and [H-3]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (K(D) values of 24 +/- 2.3 and 2.2 +/- 0.8 nM, and B(max) values of 440 +/- 35 and 1,482 +/- 110 fmol/mg of protein, respectively). The binding was temperature- and protein-dependent. Displacement studies showed a similar rank order of potency of various unlabeled ligands against both [H-3]Ro 5-4864 and [H-3]PK 11195 (PK 11195 > Ro 5-4864 > flunitrazepam > flumazenil). These results suggest that peripheral-type benzodiazepine receptors are present in the retina of the rabbit, but not of the turtle.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
