Non-neuronal endogenous GABA efflux from the rat oviduct

Exogenous gamma-aminobutyric acid addition enhances porcine sperm acrosome reaction

The widely used porcine artificial insemination procedure involves the use of liquid‐stored semen because it is difficult to control the quality of frozen–thawed porcine sperm. Therefore, there is a high demand for porcine semen. The control and enhancement of sperm function are required for the efficient reproduction of pigs. We previously reported that gamma‐aminobutyric acid (GABA) enhanced sperm capacitation and acrosome reaction in mice. In this study, we demonstrated the presence of GABA_A receptors in porcine sperm acrosome. Furthermore, we investigated the GABA effects on porcine sperm function. We did not detect any marked effect of GABA on sperm motility and tyrosine phosphorylation of sperm proteins. However, GABA promoted acrosome reaction, which was suppressed by a selective GABA_A receptor antagonist. GABA binds to GABA_A receptors, resulting in chloride ion influx. We found that treatment with 1 μM GABA increased the intracellular concentration of chloride ion in the sperm. In addition, the GABA concentration effective in the acrosome reaction was correlated with the porcine sperm concentration. These results indicate that GABA and its receptors can act as modulators of acrosome reaction. This study is the first to report the effects of GABA on porcine sperm function.

The aryl hydrocarbon receptor pathway and sexual differentiation of neuroendocrine functions

Historically, much of the research on health effects of environmental pollutants focused on ascertaining whether compounds were carcinogenic. More recent findings show that environmental contaminants also exert insidious effects by disrupting hormone action. Of particular concern are findings that developmental exposure to dioxins, chemicals that act through the aryl hydrocarbon receptor pathway, permanently alters sexually differentiated neural functions in animal models. In this review, we focus on mechanisms through which dioxins disrupt neuroendocrine development as exemplified by effects on a brain region critical for ovulation in rodents. We also provide evidence that dysregulation of GABAergic neural development may be a general mechanism underlying a broad spectrum of effects seen after perinatal dioxin exposure.