Intracisternal Octreotide Does Not Ameliorate Orthodromic Trigeminovascular Nociception

Abstract

Octreotide is a long-acting somatostatin analogue that has been effectively used to treat migraine. Octreotide poorly penetrates the blood–brain barrier, but has potential central target sites in the trigeminal nucleus caudalis, which is the primary central relay station for trigeminal nociceptive information 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 trigeminal nerves. Fos expression in the outer layers of the trigeminal nucleus caudalis (TNC I-II) and behavioural analysis were used to measure the effects of octreotide on capsaicin-induced trigeminovascular activation. Increases of head grooming and scratching behaviour are an indication of octreotide-induced trigeminal activation. However, octreotide did not alter the average capsaicin-induced Fos expression in the TNC I-II and capsaicin sensitive behaviours were not modified by octreotide pre-treatment. This argues against a role for central (TNC I-II) somatostatin receptors in the processing of the nociceptive trigeminovascular signals.