Distribution of GABA receptor ρ subunit transcripts in the rat brain

Abstract

The gamma-aminobutyric acid (GABA) receptor rho subunits recently cloned from rat and human retina are thought to form GABA receptor channels belonging to a pharmacologically distinct receptor class, termed GABA(C). In this work we have examined the distribution of rho1, rho2 and rho3 subunits, and found expression of all three transcripts in several regions of the rat nervous system. In situ hybridization revealed expression of rho2 in the adult rat retina and some other parts of the visual pathways. A high local rho2 expression was seen in the superficial grey layer of the superior colliculus, and in the dorsal lateral geniculate nucleus. Expression was also detected in the 6th layer of visual cortex and in the CA1 pyramidal cell layer of hippocampus. With reverse transcriptase-polymerase chain reaction, expression of rho1 was mainly seen in the adult rat retina and dorsal root ganglia, as well as, at a significantly lower level, in the superior colliculus, hippocampus, brain stem, thalamus, postnatal day 8 (P8) superior colliculus and P8 hippocampus. Expression pattern of rho3 mRNA was clearly different from that of rho1 and rho2, being strongest in the hippocampus, and significantly lower in the retina, dorsal root ganglia and cortex. No rho3 expression was observed in adult or P8 superior colliculus or in P8 hippocampus. The present results clearly demonstrate that expression of GABA receptor rho subunits is not restricted to the retina, but significant expression can also be detected in many other brain regions, especially in those belonging to the visual pathways. The expression pattern of the rho subunits may be helpful in solving the functional significance of the receptors formed from these subunits.

Function of γ-Aminobutyric Acid Receptor/Channel ρ1 Subunits In Spinal Cord

“…1A). Our result was consistent with previous findings of the existence of the 1 subunit in the spinal cord of mice (23,26). The precise localizations of the GABA receptor/channel 1 subunit were studied using immunohistochemistry.…”

Development of the γ-amino butyric acid (GABA)-ergic signaling system and its role in larval swimming in sea urchin

“…In addition, ciliary reversal induced by muscimol is suppressed effectively by bicuculline in Paramecium (Bucci et al, 2005). Thus, sensitivity to bicuculline might not be a crucial feature by which to distinguish vertebrate-type GABA receptors from those of invertebrates, and invertebrate GABA A Rs might not perfectly fit into the vertebrate categories in terms of their mechanisms of action (Wegelius, 2000).…”

Redox modulation of homomeric ρ1 GABAC receptors

“…Remarkably, GABA C receptors are insensitive to the GABA A competitive antagonist bicuculline (Sivilotti and Nistri 1991) and appear to be exclusively composed of q subunits (q 1 , q 2 , and q 3 ) that yield homomeric and heteromeric receptors (Zhang et al 2001). GABA C receptors are highly expressed in the retina and other visual areas, but q subunits were found to be widely distributed in the CNS (Strata and Cherubini 1994;Enz et al 1995;Albrecht et al 1997;Boue-Grabot et al 1998;Wegelius et al 1998;Enz and Cutting 1999) and their expression is developmentally regulated (Ogurusu et al 1999;Didelon et al 2002;Rozzo et al 2002;Liu et al 2004;Alakuijala et al 2005). Functional GABA C receptors were localized at many different neuronal subtypes (Feigenspan et al 1993;Strata and Cherubini 1994;Martina et al 1997;Pasternack et al 1999;Alakuijala et al 2006).…”