Impaired social behavior in chicks exposed to sodium valproate during the last week of embryogenesis.
OBJECTIVE
To evaluate direct exposure to sodium valproate (VPA) during embryogenesis, we administered VPA to chick embryos and examined their social behaviors after hatching.


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.
Department of Pharmacotherapeutics, School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Shiwa-gun, Iwate 028-3694, Japan. hnishigo@iwate-med.ac.jp
Hideo
H
Nishigori
Keisuke
K
Kagami
Ai
A
Takahashi
Yu
Y
Tezuka
Atsushi
A
Sanbe
Hidekazu
H
Nishigori
D000375:Aging / Q000523:psychology*; D000818:Animals; D001010:Anxiety, Separation / Q000503:physiopathology / Q000523:psychology*; D001522:Behavior, Animal; D001835:Body Weight / Q000187:drug effects; D001921:Brain / Q000187:drug effects / Q000503:physiopathology; D002642:Chick Embryo; D047108:Embryonic Development / Q000187:drug effects*; D007173:Imprinting, Psychological; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D009483:Neuropsychological Tests; D009929:Organ Size / Q000187:drug effects; D012919:Social Behavior; D014635:Valproic Acid / Q000494:pharmacology*; D014828:Vocalization, Animal
D014635:Valproic Acid