DISTRIBUTION OF SUBSTANCE P-LIKE IMMUNOREACTIVITY IN THE CHAMELEON BRAIN

The distribution of substance P-like immunoreactivity in the chameleon brain and spinal cord was studied with immunohistochemical methods us ing polyclonal antibodies against substance P. In the telencephalon, i mmunoreactive cell bodies and fibers were located primarily in the str iatum and in the globus pallidus. In addition, few substance P-like fi bers were observed in the cortical areas, in the septum, and in the am ygdala. In the diencephalon, a high density of immunostained neurons a nd fibers were seen in the periventricular and ventrolateral hypothala mus. Another group of cell bodies was located in the optic tectum and particularly in the stratum griseum central. A large number of immunor eactive fibers were also detected in the thalamic nuclei and in the me dian eminence. In the mesencephalon, few immunoreactive neurons were o bserved in the ventral tegmental area, in the substantia nigra, and in the nucleus reticularis isthmi. These latter nuclei, the periventricu lar area, the posterior commissure, the nucleus lentiformis mesencepha li, the oculomotor nucleus, and the raphe nuclei contained a dense ple xus of substance P immunoreactive fibers. No immunoreactive cell bodie s were observed in raphe nuclei. In the spinal cord, no substance P-li ke immunoreactive neurons were observed, but a large number of substan ce P immunostained fibers were seen in the dorsal and lateral part of the dorsal hem and surrounding the dorsal parts of the central canal. The results of the present study are discussed with respect to those o btained in other species of reptiles, the main differences concerning the lateral septum, the habenula, the area of the paraventricular orga n, and the raphe nuclei.