期刊
BRAIN RESEARCH
卷 872, 期 1-2, 页码 1-10出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0006-8993(00)02314-3
关键词
peripheral arterial chemoreceptors; A(2a)-adenosine receptor; development; carotid body; gene expression
The sensitivity of peripheral arterial chemoreceptors in the carotid body to hypoxia increases with postnatal maturation. Carotid sinus nerve activity is augmented by adenosine binding to A(2a)-adenosine receptors and attenuated by dopamine binding to D-2-dopamine receptors. In this study, we used in situ hybridization histochemistry to determine the change in the levels of mRNA expression for A(2a) and A(1)-adenosine receptors and D-2-dopamine receptors in the rat carotid body. We also investigated the cellular distribution and possible colocalization of these receptor mRNAs and tyrosine hydroxylase (TH) mRNAs during the first 2 weeks of postnatal development. By using immunohistocytochemistry, we detected A(2a)-adenosine receptor protein in the carotid body and petrosal ganglion. We found that A(2a)-adenosine receptor mRNA and protein are expressed in the carotid body in animals at 0, 3, 6 and 14 postnatal days. The level of A(2a)-adenosine receptor mRNA expression significantly decreased by 14, postnatal days (P<0.02 vs. day 0) while D-2-dopamine receptor mRNA levels significantly increased by day 3 and remained greater than D-2-dopamine receptor mRNA levels at day 0 (P<0.001 all ages vs. day 0). TH mRNA was colocalized in cells in the carotid body with A(2a) adenosine receptor and D-2-dopamine receptor mRNAs, A(1)-adenosine receptor mRNA was not expressed in the carotid body at any of the ages examined. In the petrosal ganglion, A(1)-adenosine receptor mRNA was abundantly expressed in numerous cells, A(2a)-adenosine receptor mRNA was expressed in a moderate number of cells while D-2-dopamine receptor mRNA was seen in a few cells in the rostral petrosal ganglion. In conclusion, using in situ hybridization histochemistry, we have shown that mRNA for both the excitatory, A(2a)-adenosine receptor, and the inhibitory, D-2-dopamine receptor, is developmentally regulated in presumably type I cells in the carotid body which may contribute to the maturation of hypoxic chemosensitivity. Furthermore, the presence A(1)-adenosine receptor mRNAs in cell bodies of the petrosal ganglion suggests that adenosine might also have an inhibitory role in hypoxic chemotransmission. (C) 2000 Elsevier Science B.V. All rights reserved.
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