The
analgesic activity of (-)-
linalool (LIN), a
monoterpene present in
essential oils of Lamiaceae species, has been previously demonstrated in rodents. However, its possible use in the treatment of
fibromyalgia (FM) was never demonstrated. Additionally, as a short half-life is a limitation for the LIN medicinal application, the employment of drug delivery systems has been used to improve
pharmaceutical properties of this compound. We investigated the anti-nociceptive effect of LIN, isolated or in β-
cyclodextrin complex (LIN-CD), in an animal model of chronic non-inflammatory
muscle pain (a FM animal model), as well as its effect on the central nervous system (CNS). Male Swiss mice were subjected to two
injections of acidic saline (pH 4; 20 μL/gastrocnemius) and were treated on alternate days, with LIN-CD (25 mg/kg, p.o.), LIN (25 mg/kg, p.o.),
tramadol (TRM 4 mg/kg, i.p.), or vehicle (neutral saline). After 60 min, they were screened for
mechanical hyperalgesia (von Frey), motor coordination (rotarod), and muscle strength (grip strength meter) for 27 days. The CNS areas involved in the anti-hyperalgesic activity were evaluated by immunofluorescence. LIN or LIN-CD produced a significant reduction (p < 0.001) of
mechanical hyperalgesia on chronic non-inflammatory
muscle pain model, which remained for 24 h only in LIN-CD, and these compounds significantly (p < 0.05) activated neurons of the locus coeruleus, nucleus raphe magnus, and periaqueductal gray areas. So, our results suggest that LIN-CD improved
analgesic profile of LIN, with a probable involvement of descending
pain pathways and the anti-nociceptive effect of
linalool in an animal model of chronic non-inflammatory
muscle pain. So far, only the investigations in animal models of inflammatory
pain and supraspinatus were published.