Calcitonin gene-related peptide gene expression in the spontaneously hypertensive rat

Calcitonin gene-related peptide, a product of the calcitonin gene, is a potent vasodilator neuropeptide. We have demonstrated that dietary calcium deficiency decreased the neuronal (laminae I/II of the dorsal horn of the spinal cord) content of immunoreactive calcitonin gene-related peptide in the normal rat. Neuronal calcitonin gene-related peptide levels are also reduced in the spontaneously hypertensive rat, a model characterized by calcium deficiency. However, the mechanism of this reduction in neuronal calcitonin gene-related peptide could be due to decreased synthesis or increased release. To determine if neuronal calcitonin gene-related peptide messenger RNA (mRNA) levels are also decreased in the spontaneously hypertensive rat, we measured relative calcitonin gene-related peptide mRNA levels (using a genomic hybridization probe specific for alpha- and beta-calcitonin gene-related peptide mRNA) in dorsal root ganglia from spontaneously hypertensive and Wistar-Kyoto control rats. Dorsal root ganglia neuronal cell bodies are a prominent site of calcitonin gene-related peptide synthesis and send axons to peripheral blood vessels and central spinal cord sites (laminae I/II). After normalization of calcitonin gene-related peptide mRNA levels of 18S RNA, the calcitonin gene-related peptide mRNA/18S RNA ratio was significantly decreased approximately threefold in the spontaneously hypertensive rats compared with controls. This alteration in calcitonin gene-related peptide mRNA levels is specific for dorsal root ganglia, because no strain differences in calcitonin gene-related peptide mRNA content were detected in heart or brain.(ABSTRACT TRUNCATED AT 250 WORDS)