Angiotensin II type 1 receptor activation facilitates pain hypersensitivity via dorsal horn pericyte mediated vasoconstriction

Abstract

Vascular disturbance is a key factor in the development of neurological disease, with reduced integrity of the capillary network in the dorsal horn implicated in activation of nociceptive neural circuits and induction of pain hypersensitivity. Pericytes regulate capillary health and tone, with pericyte dysfunction in cerebral tissue associated with neurodegenerative disorders. Our work demonstrates that nociceptive processing is influenced by angiotensin II type 1 (AT1) receptor mediated pericyte contractility in the dorsal horn. Intravital imaging of the mouse spinal cord demonstrated angiotensin II induced cessation of spinal cord capillary perfusion. Intrathecal administration of angiotensin II induced pericyte contractility and narrowing of capillary diameter, which was accompanied by mechanical allodynia and heat hyperalgesia. Angiotensin II mediated pericyte activation and reduction of spinal cord blood flow, was prevented by inhibition of AT1 receptor via losartan treatment. In addition, losartan either systemically or intrathecally administered, prevented angiotensin II induced pain in male and female adult mice. This was associated with protection of the dorsal horn capillary endothelium, with intrathecal co-treatment with losartan preventing loss of CD31 immunoreactivity in the dorsal horn following administration of angiotensin II. This investigation demonstrates that AT1 mediated pericyte regulation of the dorsal horn capillary network, is fundamental in modulating nociceptive processing and perception of pain. Here we identify a novel cellular and mechanistic target for the development of new analgesic.