Comparative Analysis of Vasotocin-Like Immunoreactivity in the Brain of the Turtle <i>Pseudemys scripta elegan </i><i>s</i> and the Snake <i>Python regiu</i><i>s</i> (Part 2 of 2)

Abstract

The distribution of vasotocin in the brains of the turtle Pseudemys scripta elegans and the snake Python regius was studied with immunohistochemical methods. In both species, vasotocin-immunoreactive (VTi) cells were found in the supraoptic nucleus, the paraventricular nucleus and the bed nucleus of the stria terminalis. No VTi cell bodies were seen in the brainstem. Vasotocinergic fibers were found in all major brain divisions. Intrahypothalamic VTi fibers were observed between the supraoptic and the paraventricular nuclei and in the median eminence? An extensive network of extrahypothalamic VTi fibers extends from the olfactory bulb to the spinal cord. Limbic structures, such as the nucleus accumbens, the septal area and the ventral amygdaloid nucQsus, contain a moderate to dense VTi plexus. Other areas with a substantial number of VTi fibers are the lateral habenular nucleus, the ventral tegmental area, the substantia nigra, the locus coeruleus and the nucleus of the solrmxy tract. Sex-related differences in the density of the VTi fibers were observed in the lateral septal nucleus, the midbrain periaqueductal gray and, to a lesser extent, in the ventral amygdaloid nucleus, the lateral habenular nucleus, the ventral tegmental area and the substantia nigra. In these areas, the density of VTi fibers is higher in males than in females. The distribution of vasotocin-like immunoreactivity in the brains of Pseudemys and Python resembles the pattern previously observed in the lizard Gekko gecko. However, among the three species several differences exist, the most remarkable one being the variation in number of liquor-contacting VTi cells in the paraventricular nucleus.

Arginine Vasotocin, the Social Neuropeptide of Amphibians and Reptiles

“…In comparison to lizards, turtles and snakes have fewer AVT-containing nuclei, and only the SON and PVN have been reported to have the neuropeptide in the turtle Mauremys caspica and in the snakes Natrix maura and Bothrops jararaca ( 27 , 29 ). The BNST also contains AVT cells in the turtle Pseudemys scripta elegans and the snake Python regius ( 28 ).…”

“…Boyd and Moore ( 35 ) reported AVT concentrations, as measured with radioimmunoassay, to be higher in males than in females in the La, optic tectum, and tegmentum, but in the dorsolateral nucleus of the mesencephalon AVT concentration was higher in females. Less work on AVT sex differences has been done in reptiles, but males have been reported to have a higher density of AVT fibers than females, particularly in the PAG and Ls ( 19 , 20 , 28 ), Dc ( 22 ), and in the amygdala, BNST, NAcc, and POA in addition to the Ls ( 26 ) in a variety of species.…”