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Distribution of FMRFamide-like immunoreactivity in the brain of the lungfish Protopterus annectens
M Vallarino1, M Feuilloley, J L Thoumas
1Institute of Comparative Anatomy, University of Genova, Italy.
Abstract:
The distribution of FMRFamide-like immunoreactive peptides was studied in the brain of the African lungfish, Protopterus annectens, using the indirect immunofluorescence technique. The main populations of FMRFamide-positive cell bodies were detected in the forebrain and in the mesencephalic tegmentum. In the telencephalon, only a small number of FMRFamide-immunoreactive neurons was localized at the level of the subpallium, in the nucleus septi medialis. The diencephalon contained two prominent groups of FMRFamide-positive cell bodies located in the preoptic and periventricular preoptic nuclei. The thalamus exhibited only scattered FMRFamide-immunoreactive perikarya in its ventral part. In the mesencephalon, a group of positive cell bodies was identified in the caudal region of the tegmentum. A strong immunoreaction was also detected in the nervus terminalis. In the pituitary, most of the cells of the intermediate lobe were brightly stained. FMRFamide-like immunoreactive fibers and nerve terminals were widely distributed in the brain. In the telecephalon, numerous fibers were observed in several regions of the pallium and subpallium. A dense plexus of fibers was found in the hypothalamus and the thalamus. Immunoreactive fibers were seen coursing along the ventral wall of the infundibular cavity and terminating in the pars nervosa of the pituitary. The tectum and the ventral mesencephalon were also densely innervated. In contrast, the caudal brainstem only showed scarce immunoreactive processes. Coexistence of FMRFamide- and neuropeptide Y-like immunoreactivity was observed in the preoptic nucleus and in the nervus terminalis. The widespread distribution of FMRFamide-immunoreactive neurons in the brain and pituitary of P. annectens suggests that the peptide may exert both neuromodulator and neuroendocrine functions. The similarity between the distribution patterns of FMRFamide and neuropeptide Y in the brain of lungfish and amphibians supports the concept of a close phylogenetic link between these two groups.
Insights
This study maps FMRFamide-like peptides in the African lungfish brain, revealing widespread distribution suggesting neuromodulatory and neuroendocrine roles. Similar patterns to amphibians hint at close phylogenetic links.
Area of Science:
- Neuroscience
- Comparative Anatomy
- Peptide Research
Background:
- FMRFamide-like peptides are known neuromodulators in various species.
- Understanding their distribution in primitive vertebrates like lungfish offers evolutionary insights.
Purpose of the Study:
- To map the distribution of FMRFamide-like immunoreactive peptides in the brain and pituitary of the African lungfish, Protopterus annectens.
- To investigate potential neuromodulatory and neuroendocrine functions of these peptides.
- To explore phylogenetic relationships based on peptide distribution patterns.
Main Methods:
- Indirect immunofluorescence technique was employed.
- Detailed mapping of FMRFamide-positive cell bodies, fibers, and nerve terminals across brain regions.
- Investigation of co-localization with Neuropeptide Y.
Main Results:
- FMRFamide-positive cell bodies were prominent in the forebrain and mesencephalic tegmentum.
- Widespread FMRFamide-like immunoreactive fibers and terminals were observed throughout the brain and pituitary.
- Co-existence with Neuropeptide Y was noted in specific nuclei and the nervus terminalis.
Conclusions:
- The extensive distribution suggests FMRFamide-like peptides play significant neuromodulator and neuroendocrine roles in lungfish.
- Observed distribution patterns in lungfish share similarities with amphibians, supporting a close phylogenetic connection.
- This study enhances our understanding of neuropeptide evolution in vertebrates.