Morphological and biochemical studies on the innervation of the testis of Salamandra salamandra (L.) (Amphibia, Urodela).

The innervation of the male gonad of Salamandra salamandra was studied by fluorescence microscopy using the glyoxylic acid method, acetylcholinesterase histochemistry, electron microscopy using glutaraldehyde/osmium tetroxide and chromate/dichromate fixation, and high-performance liquid chromatography (HPLC) with electrochemical detection of biogenic amines in homogenates of the testicular tissue. Noradrenaline has been found to be the prevailing neurotransmitter in the testicular nerves; dopamine could be identified only in minor concentration. The relatively scarce noradrenergic innervation is mainly restricted to the connective tissue septa between the immature and the mature part of the testis and between the mature part and the glandular tissue. Most of the fluorescent fibers have a close connection to blood vessels. After chromate/dichromate fixation the nerve profiles contain in most cases small vesicles with electron-dense reaction products, indicating the presence of catecholamines. Varicosities are to be found near the capillaries, in the vicinity of vascular (in the wall of arterioles) and non-vascular (near the testicular surface) smooth muscle cells; no relationships were found between nerve fibers and glandular (steroid hormone-secreting) or germinal cells. Cholinergic fibers could not be identified, non-adrenergic/non-cholinergic fibers were present only in very small numbers.