Cellular Localization of GABA and GABA_B Receptor Subunit Proteins During Spermiogenesis in Rat Testis

Abstract

ABSTRACT:The GABAergic system, a major inhibitory regulator in the central nervous system, may also play important roles in peripheral nonneuronal tissues and cells. Recent studies showed that GA-BA B receptor is expressed in testis and sperm. To understand the role of the GABAergic system in spermiogenesis, we examined cellular localization of GABA and GABA B receptor subunits in rat spermatids by immunocytochemistry. Immunoreactivity for GABA was detected around acrosomal granules of spermatids during the Golgi and cap phases. GABA B(1) immunoreactivity was observed in the acrosomal vesicle of spermatids in Golgi phase, and during cap phase, this reactivity expanded to the entire region of the acrosome covering the nuclear membrane. The level of reactivity decreased gradually with maturation of spermatids. In contrast, GABA B(2) immunoreactivity was not observed in spermatids during Golgi phase but was detected in the equatorial region during cap phase. Both GABA immunoreactivity and GABA B(2) immunoreactivity were transferred to the residual cytoplasm during the release of spermatozoa. Electron microscopic immunocytochemistry revealed that, during cap phase, GABA and GABA B(1) were distributed within the whole acrosomal vesicle but not in the acrosomal granule. GABA B(2) immunoreactivity was observed in the narrow space between the inner acrosomal and nuclear membrane and was limited to the equatorial region of the spermatid head. These results indicate that the GABAergic system might be involved in regulation of spermiogenesis.

GABA exists as a negative regulator of cell proliferation in spermaogonial stem cells

“…It has now become clear that GABA signaling also exists in peripheral organs. The testes have well-described components of the GABA system, including the three types of GABA receptor, GABA synthetic enzymes (GAD65 and GAD67), and a GABA transporter (GAT-1) [10][11][12][13][14]. However, very little is known about the precise roles and underlying mechanisms of GABA signaling during spermatogenesis.…”

Expression of gamma-aminobutyric acid receptors on neoplastic growth and prediction of prognosis in non-small cell lung cancer

“…In fact, GABA has been shown to be involved in the development of many tissues and organs, including the peripheral nervous system [7], the development of the palate [8], lung [9], pancreas [10], digestive tract [11], liver [12], chondrocytes [13], testicular cells [14] and even stem cells [15]. …”

Activation of GABAAReceptor/Cl−Channel and Capacitation in Rat Spermatozoa: HCO3−and Cl−are Essential

“…The presence of GBRC on porcine and ram sperm membranes has been demonstrated using radioligand assays [Erdo and Wekerle 1990;Ritta et al 1998]. GABA A receptor subunits have been identified by immunocytochemical staining on the equatorial segment of the human sperm head [Ewert et al 1990;Wistrom and Meizel 1993] and on the ventral surface of the acrosome of rat sperm [Hu et al 2002b;Kanbara et al 2005]. The specific subunits of GBRC with molecular weight approximate 53 KDa and 75 KDa were identified by Western blot analysis [Ewert et al 1990;Wistrom and Meizel 1993;Hu et al 2002b].…”