Both presynaptic nicotinic-like and muscarinic-like autoreceptors regulate acetylcholine release at an identified neuro-neuronal synapse of Aplysia.

Abstract

The possible involvement of cholinergic presynaptic receptors regulating evoked quantal acetylcholine (ACh) release was investigated at an identified cholinergic neuro-neuronal synapse in the buccal ganglion of Aplysia, using cholinergic agonists (carbachol, pilocarpine, oxotremorine) and/or antagonists (curare, atropine, hexamethonium). Bath applied carbachol or pilocarpine (10(-8) M to 10(-4) M) induced a decrease in the evoked quantal release of ACh. As the effects of carbachol were prevented by atropine (5.10(-6) M) and not by curare (10(-5) M), it was concluded that carbachol activated presynaptic muscarinic-like receptors implicated in a negative feed-back on ACh release. On the contrary, oxotremorine (up to 10(-4) M) induced a potentiation of ACh release which was suppressed by curare (4.10(-6) M) or hexamethonium (10(-5) M) but not by atropine (5.10(-6) M) pointing to the activation of presynaptic nicotinic-like receptors implicated in a positive feed-back on ACh release. Moreover, in the presence of curare, oxotremorine decreased ACh release: this suggested that oxotremorine also activated the presynaptic muscarinic-like receptors. These results revealed the conjoint presence, on the same terminal, of both muscarinic-like and nicotinic-like autoreceptors.

• Authors: P Fossier, B Poulain, G Baux, L Tauc
• Journal: Pflugers Archiv : European journal of physiology (Pflugers Arch) Vol. 411 Issue 4 Pg. 345-52 (Apr 1988) ISSN: 0031-6768 [Print] Germany
• PMID: 2899868 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Hexamethonium Compounds
• Receptors, Muscarinic
• Receptors, Nicotinic
• Pilocarpine
• Hexamethonium
• Oxotremorine
• Muscarine
• Curare
• Carbachol
• Acetylcholine

Topics

• Acetylcholine (metabolism)
• Animals
• Aplysia (physiology)
• Carbachol (pharmacology)
• Curare (pharmacology)
• Hexamethonium
• Hexamethonium Compounds (pharmacology)
• Muscarine (physiology)
• Oxotremorine (antagonists & inhibitors, pharmacology)
• Pilocarpine (pharmacology)
• Receptors, Muscarinic (physiology)
• Receptors, Nicotinic (physiology)
• Synapses (metabolism)