Fig. 7. Synergic effects of 10^–7 mol l^–1 tryptamine (Trypt) and other drugs such as acetylcholine (Ach, 10^–3 mol l^–1), dopamine (Dop, 10^–4 mol l^–1) and taurine (Taur, 10^–3 mol l^–1) on maximal light emission (L_max) of O. californica. Values (means ± S.E.M.) are expressed as a percentage of photogenesis triggered by 200 mmol l^–1 KCl in normal artificial seawater. **P<0.01 in comparison to 10^–7 mol l^–1 tryptamine on its own; N=8 stimulated aliquot parts per treatment.