FORMATION OF NEW SENSORY CELLS IN DEAFFERENTED TUBEROUS ORGANS OF THEGYMNOTID FISH EIGENMANNIA-VIRESCENS

The cutaneous electroreceptor ''tuberous organs'' of the lateral line system of Eigenmannia virescens were studied at light and electron mic roscopic levels with immunohistochemical and autoradiographic techniqu es after sectioning of the posterior branch of the lateral line nerve, After deafferentation total degeneration of the sensory cells was obs erved, The accessory cells of the basal platform, however, remain inta ct and undergo a process of differentiation. The cytoplasms and nuclei of these cells increase in volume, and the nuclei incorporate tritiat ed thymidine, In control tuberous organs with intact innervation, trit iated thymidine is absorbed by the nuclei of the elongated epidermal c ells surrounding the sensory cavity, The newly formed sensory cells, b ut not those of the intact organs, are substance P immunoreactive, The y have synaptic bars surrounded by vesicles and their free membrane su rface is covered with microvilli, The new sensory cells are fully diff erentiated 35 days after the lateral line was cut, These results demon strate that in the tuberous organs of E. virescens new sensory cells a re formed in the absence of an innervation. (C) 1994 Wiley-Liss, Inc,