1. 1.

    The effects of cholinergic and monoaminergic drugs and blocking agents on luminescence responses of the comb-jelly Mnemiopsis leidyi were investigated, using isolated strips of meridional cells.

  2. 2.

    Catecholamines elicited dose-dependent flash activity and adrenalin was the most patent. The adrenalin response was abolished by propranolol (0.1 mmol l−1), but not phentolamine. Reserpine (0.1 mmol l−1) suppressed the flash response to electrical stimulation without affecting the adrenalin response.

  3. 3.

    Acetylcholine (ACh) elicited flash activity which was propagated along the meridional canals. Eserine (0.01 mmol l−1) potentiated the flash response to either ACh or electrical stimulation.

  4. 4.

    Tubocurarine reduced or abolished responses to either ACh or electrical stimulation. Atropine elicited intense flash activity and potentiated the response to electrical stimulation, but failed to block the ACh response.

  5. 5.

    Prolonged exposure of meridional canals to serotonin (5-HT) depressed or abolished flash responses to ACh, adrenalin and electrical stimulation.

  6. 6.

    The ACh flash response was abolished by propranolol but the response to adrenalin was not altered by tubocurarine. It is concluded that nicotinic cholinergic and beta-adrenergic mechanisms are interrelated and indirectly involved in excitation of luminescence in Mnemiopsis.

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