Isotocinergic neurons in the goldfish hypothalamus: physiological and morphological studies on chemically identified cells.

Isotocinergic (IT) neurons show physiological and morphological characteristcs that are similar to those of the other preoptic neuroendocrine cells in the goldfish. Preoptic IT cells show resting membrane potentials of 20-55 mV, action potentials of up to 100 mV, and physiological evidence of axonal branching. Dye-marked IT cells measure 14-56 micrometers, their dendrites projecting to the ependyma and into the hypothalamic neuropil, their multiple beaded axons projecting to the pituitary. Indirect immunofluorescence identifies these dye-marked cells as IT. By combining electrophysiological, dye-marking and immunocytochemical techniques we can now, for the first time, study single, antidromically-identified peptidergic neurons of a specific type in vertebrate and invertebrate species.