INTRACELLULAR DYE-MARKED ENKEPHALIN NEURONS IN THE MAGNOCELLULAR PREOPTIC NUCLEUS OF THE GOLDFISH HYPOTHALAMUS

A method that combines intracellular recording, dye marking, and immunocytochemistry makes the study of functional and morphological aspects of enkephalin neurons in the magnocellular preoptic nucleus of the goldfish hypothalamus feasible. By use of multiple techniques, enkephalin neurons can be distinguished from other brain cells and can be reconstructed from drawings of serial sections containing the dye-injected opioid cells. These enkephalin cells and their processes measure 14-42 μm in somata diameter and are unipolar, bipolar, or multipolar. Their electrophysiological properties match those of other mammalian and fish magnocellular endocrine cells. This report confirms the one neuron-one hormone (peptide) hypothesis, supports synaptic over electrotonic coupling between enkephalin and adjacent hypothalamic neurons, and suggests that chemical and functional classification of single electrophysiologically and neuroanatomically studied central neurons can be achieved.