Pharmacology, induction, and localization of embryonic chick retina muscarinic receptors

I have investigated the pharmacology, molecular biology, induction, and localization of two molecular weight subtypes of chicken retina muscarinic acetylcholine receptors (mAChR). I present evidence that both subtypes have M3 pharmacology, that retina expresses a 3.3 kB mAChR mRNA, that a developmentally-regulated activity induces expression of the 72 kDa subtype, and that cultured retina cells segregate mAChR to dendrites.; Retina mAChR pharmacology was characterized using the drugs AF-DX 116, 4-DAMP, dicyclomine, HHSiD, and pirenzepine. Binding data best fit one-site models, and mAChR affinity for these drugs was most similar to that of M3 receptors. These data indicate that both mAChR subtypes are of the M3 pharmacological class.; A 2.3 kB chicken mAChR cDNA clone was used to characterize retina mAChR mRNA. This clone hybridized with a single RNA band of 3.3 kB. Detection of a single band of retina mAChR RNA is consistent with the detection of a single class of mAChR binding sites.; Induction of the 72 kDa subtype, which is associated with retina synaptogenesis (Large et al., Proc. Natl. Acad. Sci. USA 82: 8785, 1985), was investigated in monolayer cultures. A role for cell-cell interactions was supported by the finding that mature expression of the 72 kDa subtype was associated with a high, but not a low plating density. Media conditioned by older, but not younger high density cultures induced mature levels of the 72 kDa subtype in low density cultures. I concluded that a developmentally-regulated activity can increase expression of the 72 kDa mAChR subtype.; Localization of mAChR in the embryonic chick retina system was examined in high density cultures and in low density cultures fed conditioned media (CM) using autoradiographic methods. In both types of cultures, cells were observed expressing mAChR on cell bodies as well as on dendrites. However, in both high density and CM-fed low density cultures, numerous cells segregated mAChR to dendrites. These data indicate that under culture conditions which promote or mimic cell-cell interactions, retina cells can segregate mAChR to dendrites.