Innervation of amphibian reproductive system. Histological and ultrastructural studies

- The innervation of the amphibian ovary and oviduct is described for the first time.
- Both organs show nerves fibers placed near blood vessels and smooth muscles fibers.
- Ultrastructure of axons and their terminals are characteristic of autonomic fibers.
- Nerve fibers present an immunopositive reaction to TH and NPY.
- The innervation belongs to sympathetic division of the autonomic nervous system.

In the present study we describe for the first time in anuran amphibians the histological and ultrastructural characteristics of innervation in the female reproductive organs. The observations in Rhinella arenarum revealed the presence of nerve fibers located predominantly in the ovarian hilium and in the oviduct wall. In both organs the nerves fibers are placed near blood vessels and smooth muscles fibers. In the present study the histological observations were confirmed using antibodies against peripherin and neurofilament 200 proteins. Ultrastructural analyses demonstrated that the innervation of the reproductive organs is constituted by unmyelinated nerve fibers surrounded by Schwann cells. Axon terminals contain a population of small, clear, translucent vesicles that coexist with a few dense cored vesicles.The ultrastructural characteristics together with the immunopositive reaction to tyrosine hydroxylase of the nerve fibers and the type of synaptic vesicles present in the axon terminal would indicate that the reproductive organs of R. arenarum females are innervated by the sympathetic division of the autonomic nervous system.