Intracisternal octreotide does not ameliorate orthodromic trigeminovascular nociception

Octreotide is a long-acting somatostatin analogue that has been effectively used to treat migraine. Octreotide poorly penetrates the blood-brain barri er, but has potential central target sites in the trigeminal nucleus caudal is, which is the primary central relay station for trigeminal nociceptive i nformation in the brain. We studied the effect of intracisternally applied octreotide in a model of trigeminovascular stimulation in the unrestrained rat using intracisternal capsaicin infusion to stimulate intracranial trige minal nerves. Fos expression in the outer layers of the trigeminal nucleus caudalis (TNC I-II) and behavioural analysis were used to measure the effec ts of octreotide on capsaicin-induced trigeminovascular activation. Increas es of head grooming and scratching behaviour are an indication of octreotid e-induced trigeminal activation. However; octreotide did not alter the aver age capsaicin-induced Fos expression in the TNC I-II and capsaicin sensitiv e behaviours were not modified by octreotide pretreatment. This argues agai nst a role for central (TNC I-II) somatostatin receptors in the processing of the nociceptive trigeminovascular signals.