ACTH Activity in the Pituitary and Brain of the Least Brook Lamprey, Lampetra aepyptera

A rat adrenal bioassay detected low levels of ACTH activity in the pituitary and brain of larval and adult Lampetra aepyptera, a nonparasitic lamprey. This is the first substantial evidence for the existence of this hormone in any cyclostome. Research on the lamprey pituitary has not revealed whether these cyclostomes possess the same pituitary cell types and trophic hormones as other vertebrates (Percy et al., 1975). For example, Weisbart er al. (1980) indicate that there is no sub-stantive evidence for the presence of ACTH in cyclostomes. The report of ACTH in Myxine and Lampetra (Strahan, 1959) is unreliable in view of the insensitivity of the bioassay and the absence of experimental details and quantitative data. As evidence