Effect of monosodium glutamate on the neural complex of Ciona intestinalis (Tunicata).

Short-term treatment of the ascidian (tunicate) Ciona intestinalis with monosodium glutamate produces a transient decrease in methionine-enkephalin-like immunoreactivity of neurones in the nervous ganglion. Moreover, it causes vacuolisation of the cells in the neural complex, particularly in the neural gland. Similar damages occur after ovariectomy. These results suggest that the ovary exerts an indirect influence on the neural gland via the nervous ganglion, and that the methionine-enkephalin-like substance could be the responsible "neuromediator".