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

Summary Isotocinergic (IT) neurons show physiological and morphological characteristics that are similar to those of other preoptic neuroendocrine cells in the goldfish. Preoptic IT cells show resting membrane potentials of 20–55 mV, action potentials of up to 100mV, and physiological evidence of axonal branching. Dye-marked IT cells measure 14–56 m, their dendrites projecting to the ependyma and into the hypothalamic neuropil, their multiple beaded axons projecting to the pituitary. Indirect immunofluorescence identifies these dyemarked 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.Supported by Grants from the USPHS (NS-13411 and NS-05696)The authors wish to thank Ms. S. Curtis for editorial assistance, Ms. D. Cronce for skillful technical assistance, Dr. W.W. Stewart for helpful suggestions and for his generous gift of Lucifer Yellow-CH, Dr. M. Manning for his generous gift of high quality peptides, and Dr. R.R. Dries and J.D. Fernstrom for kindly supplying antisera