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Impaired social behavior in chicks exposed to sodium valproate during the last week of embryogenesis
Hideo Nishigori1, Keisuke Kagami, Ai Takahashi
1Department of Pharmacotherapeutics, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Shiwa-gun, Iwate 028-3694, Japan. hnishigo@iwate-med.ac.jp
Insights
Exposure to sodium valproate (VPA) during chick embryogenesis impaired social behaviors, including aggregation, belongingness, and vocalization, despite normal motor skills. This study introduces a novel animal model for assessing developmental impacts on social behavior.
Area of Science:
- Developmental neuroscience
- Behavioral biology
- Teratology
Background:
- Prenatal exposure to certain medications can impact neurodevelopment.
- Valproic acid (VPA) is a known teratogen with potential neurodevelopmental effects.
- Understanding the specific impacts of VPA on social behavior is crucial.
Purpose of the Study:
- To investigate the effects of direct sodium valproate (VPA) exposure during chick embryogenesis on post-hatching social behaviors.
- To establish a chick embryo model for studying the influence of in-utero environmental factors on social development.
Main Methods:
- Chick embryos were exposed to sodium valproate (VPA) on day 14 of incubation.
- Hatchlings' motor, imprinting, and surface righting abilities were assessed.
- Social behaviors were evaluated using aggregation, belongingness, and vocalization tests on posthatching day 3.
- Cerebellar weight was measured post-mortem.
Main Results:
- VPA-exposed chicks exhibited normal hatching, motor, imprinting, and surface righting abilities.
- Significantly impaired social behaviors were observed in VPA-exposed chicks, including slower aggregation and belongingness, and reduced vocalization.
- VPA exposure led to a 15% reduction in cerebellar weight compared to controls.
Conclusions:
- In-utero exposure to VPA during late embryogenesis results in deficits in social behaviors in chicks.
- These social impairments occur despite normal early-life motor and imprinting capabilities.
- The chick embryo model offers a valuable tool for assessing the long-term effects of prenatal exposures on social behavior.
Rationale And Objectives:
To evaluate direct exposure to sodium valproate (VPA) during embryogenesis, we administered VPA to chick embryos and examined their social behaviors after hatching.
Methods And Results:
Embryos treated with VPA (35 μmol/egg) on day 14 were similar to controls for hatching date (day 21) and hatchlings' abilities, such as motor, imprinting, and surface righting. However, these VPA chicks on posthatching day 3 scored significantly low in the chick's social separation stress (SSS) test as follows. Aggregation test evaluated the speed of four chicks, individually isolated by a cardboard in a box, to aggregate upon removal of the cardboards. Belongingness test evaluated the speed of a chick isolated at a corner to join the group of three chicks placed at the opposite corner. Vocalization test for each chick was performed in an isolated corner by using a sound level meter. The results demonstrated that compared with controls, VPA chicks were significantly slow in aggregation (12.7 ± 2.5 s vs. 2.9 ± 0.9 s, p = 0.006) and belongingness (3.6 ± 0.28 s/40 cm vs. 2.6 ± 0.14 s/40 cm, P = 0.003) and weak in vocalization (13.4 ± 2.8 dB/30 s vs. 26.7 ± 1.3 dB/30 s, P = 0.001), respectively. Weight of cerebellum of VAP chick was 15 % lighter than controls (P = 0.004).
Conclusions:
Chick embryos exposed to VPA during the last week of embryogenesis had impaired social behaviors in spite of normal mortar and imprinting ability. The present method will be a useful animal model for assessing the effects of environment during embryogenesis on social behaviors in later life.
