Effects of acetylcholine and cholinolytics on the synaptic transmission in the ampullae of Lorenzini of the skate.

1. The effects of ACh, D-tubocuraine and atropine on the electrical activity of the ampullae of Lorenzini of the skate were studied. 2. ACh (10(-5)M) caused an increase in frequency of afferent discharges in all receptors under study. 3. When excitability was abolished by high Mg2+ solution (50 mM) perfusion with 50 mM Mg2+ plus ACh did not induce firing in the afferent fibres. 4. Cholinergic antagonists (D-tub and atr) did not block the synaptic transmission. 5. The results suggest that ACh is unlikely to be the synaptic transmitter in the ampullae of Lorenzini.