An in vitro study on noradrenergic modulation of final oocyte maturation in the catfish Heteropneustes fossilis

This study was aimed to elucidate in vitro the effects of endogenous catecholamines: dopamine (DA), noradrenaline (NA) and adrenaline (A), and the β-adrenergic blocker propranolol on induction of final oocyte maturation (FOM) in the catfish Heteropneustes fossilis. With this aim, post vitellogenic follicles from sexually mature gravid female catfish were incubated with each of DA, NA and A in a concentration range of 5-250 μM, and propranolol in a concentration range of 1-200 μg/mL at time points varying from 0 to 30 h). Translucent follicles without germinal vesicle (GV) and opaque follicles with GV were scored separately for the calculation of percentage germinal vesicle breakdown (GVBD), an index of FOM. Data were analyzed by one-way ANOVA and were considered statistically significant when P values were less than 0.05. The analysis of the data showed that the incubation with NA only stimulated GVBD in a concentration - and time-dependent manner. Though the incubation with propranolol decreased total follicular cAMP level significantly at and above 10 μg/mL concentrations, a significant effect of the GVBD increase was noticed at 50 μg/mL or higher. However, the 10 μg/mL concentration of propranolol was effective to inhibit the NA-induced GVBD significantly albeit at a low level (39%). The present study suggests that final oocyte maturation is modulated by NA through a β-adrenergic mechanism, implicating a neural control of oocyte maturation and ovulation in teleosts.