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Analysis of the change in number of serotonergic neurons in the chick spinal cord during embryonic development
Insights
Serotonin (5-HT) neurons in chick embryos appear early and increase by E12. Despite a later decrease, these spinal cord 5-HT cells persist throughout development, not just transiently.
Area of Science:
- Neuroscience
- Developmental Biology
- Embryology
Background:
- Serotonin (5-HT) plays crucial roles in neuronal development and function.
- The presence and developmental trajectory of 5-HT neurons in the embryonic spinal cord are not fully understood.
Purpose of the Study:
- To investigate the existence and developmental changes of serotonin (5-HT)-containing neurons in the chick embryo spinal cord.
Main Methods:
- Utilized anti-5-HT immunocytochemistry to detect and visualize 5-HT neurons.
- Conducted quantitative analysis to estimate the number of 5-HT neurons at various embryonic ages (E7-E21/22).
Main Results:
- 5-HT immunoreactive cells were first observed at E7, initially in the floor plate.
- The 5-HT neuronal population increased from E7, plateaued around E9-E12, decreased at E17, and then increased again by hatching (E21/22).
- The number of 5-HT neurons at hatching returned to or exceeded earlier embryonic levels.
Conclusions:
- Spinal cord 5-HT neurons in chick embryos are present throughout embryonic development.
- These neurons do not appear transiently but persist from early stages to hatching.
Abstract:
The existence of serotonin (5-HT)-containing neurons in the spinal cord of the chick embryo was examined by anti-5-HT immunocytochemistry. The first immunoreactive cells were observed in embryos at 7 days of incubation (E7) and were initially located within the floor plate of the early spinal cord. By E9, immunostained cells occurred throughout the length of the spinal cord and were frequently encountered in most transverse sections of the cord. When examined at later embryonic ages of E12, 17 and at hatching (E21 or 22), the 5-HT cells became progressively more difficult to find with the advancing age of the embryos. To determine if this population of spinal cord 5-HT neurons actually diminished during development, a detailed quantitative analysis was undertaken to estimate the number of 5-HT cells in the cord of chick embryos at different ages. The results of this investigation demonstrated that the size of the 5-HT neuronal population rose rapidly from E7 and plateaued (at approximately 3500 neurons) between E9 and E12. As anticipated, the number of 5-HT cells at E17 decreased at all cord levels. Surprisingly, however, the number of spinal cord 5-HT neurons at hatching increased (depending on the cord level) either back to, or above, the counts estimated for the earlier ages of E9 and E12. Therefore, cells expressing the 5-HT phenotype in the spinal cord of the chick embryo persist throughout the period of embryonic development, rather than appear transiently.(ABSTRACT TRUNCATED AT 250 WORDS)