The effect of the biogenic amines octopamine and serotonin, and of both amines combined (cocktails) on transmitter release at neuromuscular junctions of two crustaceans was studied, octopamine (10-8 mol l-1 to 10-6 mol l-1) either enhanced or decreased evoked transmitter release through presynaptic effects. The results were identical for the slow and the fast excitor in the closer muscle of the crab, and for the excitor in the opener muscle of the crayfish. Application of serotonin always resulted in a strong increase of release. However, this potentiating effect of serotonin was reduced in strength by subsequent application of cocktails consisting of serotonin and octopamine. In all experiments, a cocktail of serotonin and octopamine was less effective than serotonin alone. The decrease in the mean quantal content m by octopamine was due to a reduction of the probability of release p. Since both amines are synthesized in the central nervous system and are released from neurohaemal organs into the haemolymph bathing the neuromuscular junctions, the results suggest that the two amines, when present together, modulate transmitter release in an antagonistic way, and that the level of the two determines synaptic efficacy.
|Number of pages||10|
|Journal||Journal of Comparative Physiology A|
|State||Published - 2001|
Bibliographical noteFunding Information:
Acknowledgements Funding was provided by the Deutsche Fors-chungsgemeinschaft (Ra 118/8-3) and the Fonds der Chemischen Industrie to W.R., and NSF grants IBN-9808631 and ILI DUE-9850907 to R.L.C. We thank Prof. Amedeo deSantis (Naples) for help in obtaining the crabs and Dr. Sabine Kreissl (Konstanz) or helpful comments on the manuscript. The experiments comply with the ``Principles of Animal Care'' publication No 86-23 revised 1985 of the NIH (USA), and also with the current laws of the respective country in which the experiments were performed.
- Biogenic amine
- Transmitter release
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology
- Behavioral Neuroscience