Distribution of dopamine immunoreactive systems in brain stem and spinal cord of the chameleon

An immunohistochemical method, using glutaraldehyde fixation and a highly specific monoclonal antibody recently synthetized against dopamine (DA)-glutaraldehyde protein conjugate, permitted direct visualization of DA structures in the brainstem and spinal cord of a reptile (Chameleon). DA-immunoreactive cell bodies occurred in some contiguous areas of the midbrain tegmentum. The first one was located in the ventral tegmental area. Some somata intermingled with the oculomotor nucleus. The second group was the large round or oval DA-Immunostained neurons located in the substantia nigra. More caudally, a third group of round or fusiform DA-cell bodies was seen in an homologous area of so called mammalian A8 and were continuous with the substantia nigra group. In the medulla oblongata, the DA-containing cells were shown in the nucleus of solitary tract and in the dorsal lateral part of the dorsal motor nucleus of the vagus. The density of this DA-Immunoreactive neurons decreased more caudally. At the medullo-spinal level and upper cervical spinal cord, a few labelled cells were distinguished near the central canal. In the spinal cord DA-immunopositive cell bodies were observed in the vicinity of the central canal and formed a continuous column that extended throughout the rostral spinal cord. The apical processes of these neurons seemed to be in contact with the lumen of the central canal. This study constitute the first visualization of the immunoreactive DA-cell bodies at the medullo-spinal level which were already described, as TH immunoreactive in other species of reptiles.