The removal of spinal glycinergic inhibition by intrathecal
strychnine produces an
allodynia-like state in rodents. Our objective was to measure spinal
prostaglandin E2 (
PGE2) release during
strychnine-
allodynia and examine the effects of Nomega-nitro-
L-arginine (L-
NOARG), an inhibitor of
nitric oxide synthetase. Under
halothane, rats were fitted with intrathecal and spinal microdialysis
catheters, and
microelectrodes implanted into the locus coeruleus for measurement of
catechol oxidation current (
CAOC) using voltammetry. Animals were then administered
urethane and treated as follows: 1) baseline control 10 min, intrathecal
strychnine (40 microg) 10 min, 10 min of hair deflection, and 2) 10-min control followed by intrathecal
strychnine (40 microg) with hair deflection for 60 min. Spinal
dialysate samples were collected for
PGE2 levels determined by using immunoassay. In separate experiments, the effect of intrathecal
strychnine (40 microg) followed by hair deflection was studied in rats pretreated with intrathecal l-
NOARG (50 nmol). After intrathecal
strychnine, hair deflection significantly increased spinal
PGE2 release (619% +/- 143%), locus coeruleus
CAOC (181% +/- 6%), and mean arterial pressure (123% +/- 2%) P < 0.05. Pretreatment with intrathecal l-
NOARG significantly inhibited
strychnine-
allodynia. In this model, hair deflection evokes spinal
PGE2 release, locus coeruleus activation, and an increase in mean arterial pressure. L-
NOARG pretreatment attenuated the locus coeruleus
CAOC, a biochemical index of
strychnine-
allodynia, suggesting a mediator role of
nitric oxide. A mediator role of
nitric oxide is also implicated, helping to explain the pathophysiology of this allodynic
pain.