In situ hybridization histochemistry and receptor autoradiography were used to determine the presence of 5-HT1B receptor messenger RNA (mRNA) and 5-HT1B receptor proteins, respectively, in rat trigeminal ganglia. Receptor autoradiography on rat trigeminal ganglia, using appropriate 5-HT1B radioligands, did not demonstrate any specific labelling. In contrast, in situ hybridization showed that many ganglion cells contain 5-HT1B receptor mRNA, suggesting the presence of presynaptic 5-HT1B receptors on trigeminovascular neurons.