Muscarinic receptors binding in retinal pigment epithelium during rat development

[³H]Quinuclidinyl benzylate (³H-QNB) specific binding of the developing rat retinal pigment epithelium (RPE) and neural retina has been examined. The binding of³H-QNB to RPE was saturable and displaced by the antagonist pirenzepine. Scatchard analysis of³H-QNB binding showed two high affinity sites to RPE, with K_B=2.6nM and 45 nM. Specific³H-QNB binding membranes from neural retina exhibited a characteristic developmental profile. RPE showed a high density of³H-QNB binding sites through all developmental periods studied. The major onset of binding sites is at the time of RPE differentiation. Our data open the possibility of muscarinic receptors being involved in differentiation and/or proliferation of RPE.