Distribution of Neuropeptide FF-Like Immunoreactivity in the Brain of Dermophis mexicanus (Amphibia; Gymnophiona): Comparison with FMRFamide Immunoreactivity

Abstract

Neuropeptide FF (NPFF) is an FMRFamide-related peptide widely distributed in the mammalian brain. NPFF immunohistochemistry labeled cell bodies in a few locations and dense fiber networks throughout the brain. Recently, the distribution of NPFF immunoreactive (NPFF-ir) cells and fibers in the brain of anuran and urodele amphibians was studied and, as in mammals, significant species differences were noted. To further assess general and derived features of the NPFF-containing neuron system in amphibians, we have investigated the distribution of NPFF-ir cell bodies and fibers in the brain of the gymnophionan Dermophis mexicanus by means of an antiserum against bovine NPFF. This distribution was compared to that of FMRFamide immunoreactivity. Major traits shared with anurans and urodeles were the abundant fiber labeling in the ventral telencephalon, hypothalamus, isthmus, ventrolateral medulla and dorsal spinal cord. In addition, in the three amphibian orders the majority of the NPFF-ir cells were located in the preoptic-hypothalamic region. However, distinct particular features were present in the gymnophionan such as the lack of NPFF-ir cells in the telencephalon, brainstem and spinal cord and the absence of NPFF-ir fibers in the hypophysis and the olfactory bulbs. This pattern was distinct from that observed for FMRFamide distribution. Striking differences were noted in the pallium, caudal hypothalamus and midbrain tegmentum where FMRFamide – containing cells were localized. The present results in Dermophis support the idea that data from gymnophionans must be included when stating the amphibian condition of a given system because important variations are obvious when gymnophionans are compared with anurans and urodeles.