Introduction:
Cannabinoid receptors (CBR) are divided into two subclasses. The subtype 2 mediates
several antiinflammatory effects that make it a valid candidate as an otoprotective
agent. We therefore investigated the ability of JWH-133, a CBR-2 agonist, to reduce
the effects of abacterial labyrinthitis on cochlear microcirculation.
Material and Methods:
40 dunkin-hartley guines pigs were divided into 8 groups of 5 animals each. In each
animal cochlear microcirculation was quantified by in-vivo fluorescence microscopy.
In the first four groups, lipopolysaccharide (LPS) was applied topically in various
concentration (1 mg/ml, 10 µg/ml, 100 ng/ml, placebo) to emulate the effects of abacterial
labyrinthitis. In the second four groups, JWH-133 (500 ng/ml), a potent CBR-2 agonist,
was applied topically before application of LPS. Microcirculation was quantified before,
30 minutes after the initial treatment and at the end of the second treatment.
Results:
30 and 60 minutes after topical application of LPS, microcirculation dropped to 79.1%
or 75.6%, respectively (1 mg/ml), to 88.8% or 81.7%, respectively (10 µg/ml) and to
96.8% or 89.3%, respectively (100 ng/ml). Application of Placebo caused no such decreases
in microcirculation (99.8% and 99.6% from the basal values). Previous application
of JWH-133 showed no changes in microcirculation (97.8% of the basal values). The
subsequent application of LPS then caused no changes in microcirculation (99.0% of
the basal values).
Conclusion:
JWH-133 is capable of abrogating the effects of abacterial labyrinthitis on cochlear
microcirculation. It therefore is a valid candidate as an otoprotective agent in bacterial
otitis media and various other inner ear pathologies.
