5HT(1B) AND 5HT(1D) RECEPTOR MESSENGER-RNA DIFFERENTIAL COLOCALIZATION WITH PEPTIDE MESSENGER-RNA IN THE GUINEA-PIG TRIGEMINAL GANGLION

To investigate the possible role of 5HT(1B) and/or 5HT(1D) receptors i n controlling neurogenic inflammation, we performed a co-localization study of the mRNA for 5HT(1B) and 5HT(1D) receptors and of substance P or calcitonin gene-related peptide (CGRP) mRNA in the guinea pig trig eminal ganglion using double labelling in situ on hybridization techni ques. The 5HT(1D) receptor mRNA is abundant whereas 5HT(1B) receptor m RNA is scarce. The vast majority of cells containing substance P mRNA also contained 5HT(1B) receptor mRNA, but very few cells expressed sub stance P mRNA and 5HT(1D) receptor mRNA. Both receptor mRNAs were co-l ocalized with CGRP mRNA. Hence, 5HT(1D) receptors may control the rele ase of CGRP only, whereas 5HT(1B) receptors may control the release of both substance P and CGRP. The question remains whether selective 5HT (1D) agonists will have migraine abortive properties.