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Ontogeny of the FMRFamide-immunoreactivity in the rat forebrain and diencephalon
1Department of Anatomy, College of Medicine, National Cheng Kung University, Taiwan, Republic of China.
Abstract:
Ontogeny of the FMRFamide (molluscan cardioexcitatory neuropeptide)-containing structures in the forebrain and diencephalon of the rat was investigated by employing immunohistochemical methods. FMRFamide-like immunoreacted (FMRF-IR) fibers first appeared in the borders of the periventricular zone and the preoptic area at embryonic day 18 (E18). Toward birth, the FMRF-IR fibers gradually increased both in immunoreactivity and in number in these areas. A pronounced increase in FMRF-IR was also found in the septum, the arcuate nucleus, the median eminence, the paraventricular nucleus and the amygdaloid complex. A few FMRF-IR fibers appeared at the prenatal stage in the caudate nucleus, the bed nucleus of the stria terminalis, the dorsomedial nucleus and the cortex. The first FMRFamide-immunoreactive neurons were seen in the caudate-putamen and the amygdaloid complex at E21. These FMRF-IR cells increased in immunoreactivity and a significant number of cells was noted in these nuclei in the adult rat. The highest density of FMRF-IR neurons, especially in the amygdala and tuberal hypothalamic area, was detected at postnatal two weeks (P15). FMRFamide-like immunoreactivity in the forebrain and diencephalon appeared in the cell fibers prior to that observed in the cell bodies. This may suggest that some of the immunoreacted fibers may have originated from the lower areas of the rat brain. High densities of FMRF-IR cells present in the embryonic and early postnatal stages may indicate that FMRFamide is an important factor involved in developmental organization of the central nervous system. These results also indicate a differential genesis of FMRF-IR neuronal groups in different regions.
Insights
FMRFamide-like immunoreactivity develops early in rat brain structures, with fibers appearing before cell bodies. This suggests FMRFamide plays a key role in central nervous system development and organization.
Area of Science:
- Neuroscience
- Developmental Biology
- Neuroendocrinology
Background:
- FMRFamide, a molluscan cardioexcitatory neuropeptide, has known roles in various physiological processes.
- Its presence and function in mammalian brains, particularly during development, are less understood.
Purpose of the Study:
- To investigate the ontogeny of FMRFamide-containing structures in the rat forebrain and diencephalon.
- To determine the developmental timeline and distribution of FMRFamide-like immunoreactivity (FMRF-IR) in the developing rat brain.
Main Methods:
- Immunohistochemical methods were employed to detect FMRFamide-like immunoreactivity.
- The study examined FMRF-IR in various brain regions from embryonic day 18 (E18) through postnatal stages.
Main Results:
- FMRF-IR fibers were observed as early as E18 in the periventricular zone and preoptic area, increasing towards birth.
- FMRF-IR neurons first appeared at E21 in the caudate-putamen and amygdaloid complex, with peak density at postnatal two weeks (P15).
- Fiber immunoreactivity preceded cell body immunoreactivity, suggesting potential origins from lower brain areas.
Conclusions:
- FMRFamide-like immunoreactivity appears early in rat forebrain and diencephalon development, with distinct temporal and spatial patterns.
- The early and widespread presence of FMRFamide suggests its critical involvement in the developmental organization of the central nervous system.
- Differential genesis of FMRF-IR neuronal groups across various brain regions was indicated.