A LHRH-like peptidergic neurotransmitter capable of ‘action at a distance’ in autonomic ganglia

Abstract

Many peptides are localized in nerve terminals, suggesting that peptides may function as neurotransmitters. But do peptides really serve as neurotransmitters and, if so, are the actions of peptidergic transmitters qualitatively different from the actions of ‘classical transmitters’? We chose to approach these questions by studying sympathetic ganglia in the bullfrog. The structural simplicity of the ganglia has enabled us to demonstrate that (i) a peptide resembling luteinizing-hormone-releasing hormone (LHRH) is a neurotransmitter, (ii) this LHRH-like peptide probably coexists with acetylcholine (ACh) in the same nerve terminals, and (iii) although the peptide transmitter is most probably released together with ACh from the same terminals that form conventional morphological synaptic contacts with sympathetic neurons, it can diffuse a far greater distance than ACh and can act on cells non-synaptically.