GAD is active in postnatal rat testis. GAD activity [cpm/μg protein] was measured in testicular tissue samples of 5–6 days old rats (D5-6, n = 10) and adult rats (Adult, n = 11). Tissue samples of adult rat testes (Co1, n = 6) and adult rat cerebella (Co2, n = 6) heated to 95°C for 5 min served as negative controls. GAD activity in adult testes is higher than GAD activity in postnatal testes. Columns with different superscripts are significantly (ANOVA/Newmann-Keuls, p < 0.001) different from each other and represent means+SEMs.