Microtubules and their relationships with other cytoskeletal components at cholinergic tectal synapses in culture.

Cholinergic synapses (identified by selective staining with tannic acid) of explant cultures of avian optic tectum were examined by electron microscopy after exposure of the cultures to a microtubule-stabilising drug, Taxol. The presynaptic components of such synapses commonly contained microtubules but they were never in close association with the presynaptic specialisation. Postsynaptically, microtubules commonly ran into, or close to, the postsynaptic density and/or were linked to it by 3-5 nm filaments, which, along with other filamentous cytoskeletal elements, were a prominent feature of tannic acid-stained cholinergic synapses. This study also provided some evidence that acetylcholine receptors may be present in both presynaptic and postsynaptic membranes at early stages of synapse formation and in the postsynaptic membrane alone at later stages.