Stability of muscarinic-cholinergic receptor activity in the deafferented retinotectal pathway

The high-affinity antagonist, 3-quinuclidinyl benzilidate (QNB), was used to analyze muscarinic-cholinergic receptor activity in the optic tectum of goldfish and optic lobe of developing chicks and adult pigeons after deafferentation. After deafferentation no significant loss of total or specific muscarinic receptor binding activity was observed in contrast to prior experiments where there was a marked and rapid loss of nictonic-cholinergic receptor binding activity, as measured by alphabungarotoxin binding. The relative stability of the muscarinic site as opposed to the instability of the nicotinic site in these experiments is discussed.