Figure 4.

GABA upregulates growth-stimulating gene expression via GABA_A and GABA_B receptors. Zebrafish larvae (n = 20) at three days post-fertilization (dpf) were treated with 10 µM of each (A) bicuculline, (B) CGP 46381, and (C) TPMPA 2 h before treatment with 25 mM GABA, and total RNA was extracted at 9 dpf. The RNA was reverse-transcribed, and synthetic cDNA was amplified to determine expression of the genes for insulin-like growth factor 1 (zIGF-1), growth hormone 1 (zGH-1), growth hormone receptor 1 (zGHR-1), and cholecystokinin A (zCCKA). zβ-Actin was used as an internal control. Densitometry analysis was conducted to determine the expression level of each gene relative to that of β-actin and illustrated (bottom). Significant differences among the groups were determined using Student’s t-test. All data are presented as mean ± standard error of the mean (*** p < 0.001). N.S., non-significant.