Distribution of GABA(B) receptor mRNAs in the rat brain and peripheral organs

GABA, the predominant inhibitory neurotransmitter present in the mammalian CNS, is also found in the periphery. GABA actions are mediated by the ionot ropic GABA(A)/GABA(C) receptors, as well as the metabotropic GABA, receptor . The rat GABA, receptor has recently been cloned and two cDNA clones have been isolated encoding two isoforms of the receptor, GABA(B)R1a and R1b. No rthern blot analysis revealed the presence of both transcripts in the rat b rain using specific cDNA probes for GABA(B)R1a and R1b, respectively. Howev er, Northern blot analysis, hybridized with a probe containing a sequence c ommon to both Isoforms, revealed specific RNAs in the rat brain and in test is, but not in other peripheral tissues. In the present study, by using the more sensitive reverse transcriptase-polymerase chain reaction with a spec ific set of primers for each isoform and Southern blot analysis, we found t hat both isoforms of the GABA(B) receptor are expressed not only throughout the brain but also in all peripheral organs examined, including heart, spl een, lung, liver, small intestine, large intestine, kidney, stomach, adrena l, testis, ovary and urinary bladder. The peripheral distribution of GABA(B )R1 mRNAs supports the notion of a physiological role for GABA in the contr ol of a wide range of peripheral organs.