Cholinergic projections in the telencephalo-habenulo-interpeduncular system of the goldfish

Experiments were performed in order to see whether acetylcholine is a neurotransmitter in the telencephalo-habenulo-interpeduncular system of the goldfish. After telencephalic ablation choline acetyltransferase decreased by 53% in the habenular nuclei but was unchanged in the interpeduncular nucleus. After combined telencephalic and habenular lesions, the enzyme level dropped by 95% in the interpeduncular nucleus. These results suggest the existence of a telencephalo-habenular and a habenulo-interpeduncular cholinergic projection in the goldfish, as previously demonstrated in mammals. Acetylcholinesterase histochemistry additionally demonstrates some similarities between the habenulae and the interpeduncular nucleus in the goldfish and in mammals.