Supraspinal basis of analgesic and clinical effects of the metabotropic glutamate mGluR1 antagonist during colonic distension in sheep

The present study examined contribution of group I mGluRs to development and maintenance changes in behavioural and clinical symptoms, cortisol and catecholamines blood plasma concentrations caused by visceral pain evoked by colonic distension (CD) in sheep. Intracerebroventricular (icv) administration of the group I mGluRs antagonist racemic mixture of DL-AP3 blocked development of visceral pain symptoms and neuroendocrinological changes in the blood plasma of sheep. This data clearly demonstrated that development and maintenance of visceral pain symptoms of CD is dependent on activation of group I mGluRs in supraspinal level and that these types of mGluR play a crucial role in modulating of acute colonic pain (colic). What is more, this is the first record of supraspinal analgesic effects of mGluR1 antagonist in sheep.