Histochemical distribution of monoamines in the hypothalamo-hypophysial region of the lamprey, Lampetra japonica.

The distribution of monoamine fluorescence was studied in the hypothalamohypophysial region of the lamprey. Groups of intensely fluorescent cells were observed in the lateral walls of the caudal part of the third ventricle. The anterior part of the neurohypophysis which is situated over the pars distalis showed weak fluorescence. The posterior part of the neurohypophysis which is contiguous to the pars intermedia contained highly fluorescent material in its rostral part. The distribution of monoamines in the lamprey neurohypophysis is compared with that in the higher vertebrates and their functional significance is discussed.