Neuroscience letters
-
Neuroscience letters · Feb 1997
Adenosine receptor activation suppresses tactile hypersensitivity and potentiates spinal cord stimulation in mononeuropathic rats.
The aim of the present study was to investigate the intrathecal (i.t.) action of a selective A1-adenosine receptor agonist, R-phenylisopropyl adenosine (R-PIA), on tactile withdrawal thresholds in a rat model of mononeuropathy produced by sciatic chronic constriction injury (CCI). An additional aim was to examine whether adenosine receptor activation is involved in the effects of spinal cord stimulation (SCS), which activates low-threshold fibers and suppresses touch-evoked pain both in patients and in experimental animals with neuropathy. Animals presenting hindlimb withdrawal to von Frey filaments with a bending force of < 7.5 g on the lesioned side (compared to > or = 35 g in the normal limb), were considered as having tactile hypersensitivity ("allodynia'). ⋯ The effect of R-PIA (3 nmol i.t.), a clearly submaximal dose, was abolished by concomitant treatment with the selective A1-adenosine receptor antagonist cyclopentylxanthine (10 nmol i.t.). In animals where SCS failed to influence tactile allodynia, concomitant i.t. administration of R-PIA (3 nmol) and SCS induced a clear-cut and long-lasting suppression of the hypersensitivity to tactile stimulation. In conclusion, adenosine receptor stimulation antagonizes tactile hypersensitivity in a CCI model of mononeuropathy and potentiates the action of spinal cord stimulation.