Is the nucleus corticalis of teleosts a new cholinergic central nervous system for vertebrates?

Acetylcholinesterase histochemistry suggests that the pretectal nucleus corticalis of teleost fish may be cholinergic. Because immunohistochemical analysis with antibodies against choline acetyltransferase provides a more reliable means of recognizing cholinergic central nervous structures, we investigated transverse brain sections of the African cichlid fish, Hemichromis lifalili and Hemichromis guttatus with standard immunohistochemical techniques and found the nucleus corticalis to contain choline acetyltransferase. This supports the hypothesis that teleosts (unlike all other known vertebrates) have a cholinergic second-order sensory (i.e. visual) circuit