Distribution of mRNA and binding sites of adrenoceptors and muscarinic receptors in the rat heart

Since there exist some obscurities in the expression of mRNAs and their receptors in the heart, we have investigated the gene expression (mRNA levels) of adrenoceptors (alpha(1A)-, alpha(1B)-, beta(1)-, beta(2)-, beta(3)-) and muscarinic receptors (M-2) and the density of receptor binding sites (alpha(1A)-, alpha(1B)-, beta(1)-, beta(2)-adrenoceptors, muscarinic receptors). Moreover, the heart regions consist of tissue rich in ganglion cells (that are of importance in heart neural circuits) and those virtually free of them (myocytes). Therefore, we have examined the differences in the distribution of mRNAs/receptor binding sites in the atrial samples of the heart rich in ganglion cells vs. those are virtually free of them. Binding sites and mRNAs of muscarinic receptors and alpha(1B)-adrenoceptors differ in their distribution in different heart regions. The mRNAs for beta(1)- and beta(2)-adrenoceptors were almost equally distributed herein, while the amount of P-adrenoceptors significantly differs in the heart regions. The alpha(1A)- and beta(3)-adrenoceptors mRNAs were also found in all investigated heart regions, but at significantly lower level and have not shown region differences. This is a new finding, especially to beta(3)-adrenoceptors, as they were not regularly found in each heart regions. alpha(1B)-adrenoceptors have similar distribution of their mRNAs and binding sites in some heart parts. Thus, we can conclude that there are noticeable differences in the presence of receptors in heart regions that contain ganglion cells in comparison to those are virtually free of them. (c) 2005 Elsevier Inc. All rights reserved.