Evidence that cannabinoid CB1 receptors regulate intraocular pressure via two opposing mechanisms

Sally Miller, Laura Daily, Maya Ploss, Iain Greig, Ruth Ross, Naga Pradeep Rayana, Jiannong Dai, Chenna Kesavulu Sugali, Weiming Mao, Alex Straiker

Research output: Contribution to journalArticlepeer-review

Abstract

The cannabinoid signaling system regulates intraocular pressure (IOP) in the mouse via a complex system that includes three receptors: CB1, GPR18 and GPR119. In each case, activating the receptor lowers IOP, but CB1 receptors are found both at sites of aqueous humor inflow and outflow. As such, knockout mice for any of these receptors would be expected to have higher-than average, or at least unchanged, intraocular pressure. The current study investigates the unexpected observation that CB1 knockout mice have lower pressure than wild type counterparts by testing various regulators of cannabinoid signaling in murine models of IOP. We now report that a CB1 antagonist has differential effects on IOP: SR141716 raises IOP in standard light cycle (SLC) but lowers IOP in reverse light cycle (RLC). This is mimicked by ABD1085, a negative allosteric modulator of CB1. CB1 inhibitors lower IOP in both normotensive and hypertensive mouse eyes. The pressure-lowering effect is absent in CB1 knockout mice. IOP rebounds after the end of treatment but shows no sign of desensitization with daily treatment for a week. Unlike the positive cannabinoid effect, antagonist effects are not sex-dependent. We propose that there are two mechanisms of action for CB1, one that lowers IOP upon activation and a second with inverse sign that lowers IOP when CB1 is antagonized. The relatively lower pressure in CB1 knockout mouse eyes suggests that this second negative regulation of IOP is dominant.

Original languageEnglish
Article number108241
Number of pages6
JournalExperimental Eye Research
Volume200
Early online date14 Sep 2020
DOIs
Publication statusPublished - Nov 2020

Keywords

  • Cannabinoid
  • CB1
  • ocular pressure
  • glaucoma
  • antagonist
  • Glaucoma
  • Antagonist
  • Ocular pressure

Fingerprint Dive into the research topics of 'Evidence that cannabinoid CB1 receptors regulate intraocular pressure via two opposing mechanisms'. Together they form a unique fingerprint.

Cite this