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Neurodevelopmental Reflex Testing in Neonatal Rat Pups
Published on: April 24, 2017
Effect of methotrexate on rostral migratory stream in newborn rats
Ayano Hirako1, Jin Sun, Satoshi Furukawa
1Department of Veterinary Laboratory Medicine, School of Veterinary Medicine, Faculty of Agriculture, Tottori University, Minami 4-101 Koyama-cho, Tottori, Tottori 680-8553, Japan.
Abstract:
Two-day-old rats were treated with subcutaneous injections of methotrexate (MTX) 5 mg/kg and 150 mg/kg, and their rostral migratory streams (RMS) were examined time-dependently. MTX treatment increased pyknotic and TUNEL-positive cells and decreased mitotic and phospho-Histone H3-positive cells at almost all time points in the vertical arm, elbow and horizontal arm regions of the RMS. There were more TUNEL-positive cells ratio in the MTX 150 mg/kg group than in the MTX 5 mg/kg group. Treatment with MTX 150 mg/kg decreased the cellularity in the vertical arm region on Postnatal day (PD) 4, but that with the MTX 5 mg/kg did not. TUNEL-positive cells ratio was the highest in the vertical arm region, followed by elbow and horizontal regions in both MTX-treated groups. TUNEL-positive cells ratio in the vertical arm and elbow regions reached their peaks on PD 4 in both MTX-treated groups, and both MTX-treatments significantly decreased Phospho-Histone H3-positive cells ratio on PDs 2.5 and 3 in the vertical arm, elbow and horizontal arm regions. The phospho-Histone H3-positive cells ratio in the vertical arm region recovered on PD4 in the MTX 150 mg/kg group. These findings suggested that RMS required a great amount of folic acid on PD 2 and that the folic acid-requirement differed depending on the anatomical region of the RMS. To our knowledge, this is the first report demonstrating the effect of MTX on the RMS and the necessity of the folic acid metabolism on RMS development in newborn rats.
Insights
Methotrexate (MTX) exposure in newborn rats harms the rostral migratory stream (RMS) development by increasing cell death and decreasing cell proliferation. This highlights the critical role of folic acid metabolism in early brain development.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- The rostral migratory stream (RMS) is crucial for neuronal migration and brain development in newborn mammals.
- Methotrexate (MTX) is a folic acid antagonist used in chemotherapy, known to affect rapidly dividing cells.
Purpose of the Study:
- To investigate the effects of MTX on the cellularity and development of the RMS in newborn rats.
- To determine the time-dependent and dose-dependent impact of MTX on RMS cellular processes.
Main Methods:
- Two-day-old rats received subcutaneous injections of MTX (5 mg/kg and 150 mg/kg).
- RMS tissues were analyzed for pyknotic cells, TUNEL-positive cells (apoptosis), mitotic cells, and phospho-Histone H3-positive cells (proliferation) at various time points.
- Cellularity was assessed in different regions of the RMS (vertical arm, elbow, horizontal arm).
Main Results:
- MTX treatment significantly increased apoptosis (pyknotic and TUNEL-positive cells) and decreased cell proliferation (mitotic and phospho-Histone H3-positive cells) in the RMS.
- Higher MTX dose (150 mg/kg) resulted in more TUNEL-positive cells and reduced cellularity in the vertical arm region compared to the lower dose (5 mg/kg).
- Apoptosis was most pronounced in the vertical arm region, followed by the elbow and horizontal arm regions, peaking on Postnatal day 4.
Conclusions:
- MTX significantly disrupts RMS development by inducing cell death and inhibiting proliferation, underscoring the importance of folic acid metabolism during early brain development.
- The RMS exhibits region-specific susceptibility to MTX, with the vertical arm being the most affected.
- These findings establish a novel link between MTX, folic acid metabolism, and RMS development in neonatal rats.
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