The peripheral-type benzodiazepine receptor ligands [3H]Ro 5-4864 and [3H]PK 11195 bind to the retina of rabbit, but not of turtle.
The binding of [3H]flunitrazepam, [3H]Ro 5-4864, and [3H]PK 11195 to membrane preparations of the retina was studied in the turtle and rabbit. Only a single population of [3H]flunitrazepam binding sites was detected in the turtle, whereas two populations appeared to be present in the rabbit. No specific binding for [3H]Ro 5-4864 and [3H]PK 11195 could be detected in the turtle. In rabbit, both ligands bound with high affinity, revealing a significant population of binding sites (KD values of 24 +/- 2.3 and 2.2 +/- 0.8 nM, and Bmax 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 [3H]Ro 5-4864 and [3H]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.
Istituto Policattedra di Discipline Biologiche dell'Università di Pisa, Italy.
G
G
Giannaccini
C
C
Martini
A
A
Lucacchini
E
E
Strettoi
M
M
Piccolino
D000818:Animals; D001570:Benzodiazepinones / Q000378:metabolism*; D005445:Flunitrazepam / Q000378:metabolism; D007546:Isoquinolines / Q000378:metabolism*; D008024:Ligands; D011817:Rabbits / Q000378:metabolism*; D011963:Receptors, GABA-A / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D014316:Tritium; D014426:Turtles / Q000378:metabolism*
D001570:Benzodiazepinones; D007546:Isoquinolines; D008024:Ligands; D011963:Receptors, GABA-A; D014316:Tritium; C028513:4'-chlorodiazepam; D005445:Flunitrazepam; C037850:PK 11195