Cannabinoids are promising
therapies to support neurogenesis and decelerate
disease progression in neuroinflammatory and degenerative disorders. Whether
neuroprotective effects of
cannabinoids are sustainable during persistent
viral infection of the CNS is not known. Using a rodent model of chronic
viral encephalitis based on
Borna Disease (BD) virus, in which 1 week treatment with the general
cannabinoid WIN 55,212-2 has been shown to be neuroprotective (Solbrig et al., 2010), we examine longer term (2 week treatment) effects of a general (CB1 and
CB2) cannabinoid receptor agonist WIN55,212-2 (1mg/kg ip twice per day) or a specific (
CB2) cannabinoid receptor agonist
HU-308 (5mg/kg ip once daily) on histopathology, measures of frontostriatal neurogenesis and gliogenesis, and viral load. We find that WIN and
HU-308 differ in their ability to protect new
BrdU(+) cells. The selective CB2 agonist HU increases
BrdU(+) cells in prefrontal cortex (PFC), significantly increases
BrdU(+) cells in striatum, differentially regulates polydendrocytes vs. microglia/macrophages, and reduces immune activation at a time WIN-treated rats appear tolerant to the anti-inflammatory effect of their
cannabinoid treatment. WIN and HU had little direct viral effect in PFC and striatum, yet reduced viral signal in hippocampus. Thus,
HU-308 action on CB2 receptors, receptors known to be renewed during microglia proliferation and action, is a nontolerizing mechanism of controlling CNS
inflammation during
viral encephalitis by reducing microglia activation, as well as partially limiting
viral infection, and uses a nonpsychotropic
cannabinoid agonist.