[Development, during ontogenetic development of gymnotids, of substance p expression in tuberous organs...

The evolution of the neuropeptidic expression of Substance P has been investigated with immunohistochemistry in the cutaneous electroreceptors, tuberous organs, during ontogenetic development of Apteronotus leptorhynchus. In the present data, antiSP antiserum has been applied to serial sections of Apteronotus leptorhynchus larvae obtained from several egg layings. Larvae were taken during development from hatching up to one hundred days old. SP immunoreactivity appeared just after hatching, in the epidermal zones which give rise to cutaneous sense organs. Four days after hatching, the tuberous organs are differentiated and immunoreactivity was observed in these organs, in both sensory cells and accessory cells. From day 30 after hatching, there was a regular decrease in the number of tuberous organs showing labelled accessory cells, and one hundred days later only 8% of tuberous organs had immunoreactive accessory cells. The adult accessory cells were no longer labelled with anti-SP antiserum. The results showed that in Apteronotus leptorhynchus, the epidermal structures which give rise to the cutaneous sensory organs were immunoreactive at a very early stage of development; this suggests that SP could have an effect upon their differentiation.