INVOLVEMENT OF NMDA RECEPTOR MECHANISMS IN JAW ELECTROMYOGRAPHIC ACTIVITY AND PLASMA EXTRAVASATION INDUCED BY INFLAMMATORY IRRITANT APPLICATION TO TEMPOROMANDIBULAR-JOINT REGION OF RATS
Xm. Yu et al., INVOLVEMENT OF NMDA RECEPTOR MECHANISMS IN JAW ELECTROMYOGRAPHIC ACTIVITY AND PLASMA EXTRAVASATION INDUCED BY INFLAMMATORY IRRITANT APPLICATION TO TEMPOROMANDIBULAR-JOINT REGION OF RATS, Pain, 68(1), 1996, pp. 169-178
The aim of this study was to examine the possible role of N-methyl-D-a
spartate (NMDA) receptor mechanisms in responses induced by the small-
fibre excitant and inflammatory irritant mustard oil injected into the
temporomandibular joint (TMJ) region of rats. The effects of the non-
competitive NMDA antagonist MK-801 were tested on the mustard oil-evok
ed increases in electromyographic (EMG) activity of the masseter and d
igastric muscles and Evans Blue plasma extravasation. Five minutes bef
ore the mustard oil injection, MK-801 or its vehicle was administered
systemically (i.v.), into the third ventricle (i.c.v.), or locally int
o the TMJ region. Compared with control animals receiving vehicle, the
rats receiving MK-801 at an i.v. dose of 0.5 mg/kg (n = 5) showed a s
ignificant reduction in the incidence and magnitude of EMG responses a
s well as in the plasma extravasation evoked by mustard oil; MK-801 at
an i.v. dose of 0.1 mg/kg (n = 5) had no significant effect on plasma
extravasation or on the incidence and magnitude of EMG responses but
did significantly increase the latency of EMG responses. An i.c.v. dos
e of 0.1 mg/kg (n = 5) or 0.01 mglkg (n = 5) had no significant effect
on plasma extravasation or incidence of EMG responses but did signifi
cantly reduce the magnitudes of the masseter EMG response; the 0.01 mg
/kg dose also significantly increased the latency of the digastric EMG
response. The magnitudes of both the masseter and digastric EMG respo
nses were also significantly reduced by MK-801 administered into the T
MJ region at a dose of 0.1 mg/kg (n = 5) but not by 0.01 mg/kg (n = 5)
; neither dose significantly affected the incidence of EMG responses o
r the plasma extravasation. These data suggest that both central and p
eripheral NMDA receptor mechanisms may play an important role in EMG r
esponses evoked by the small-fibre excitant and inflammatory irritant
mustard oil, but that different neurochemical mechanisms may be involv
ed in the plasma extravasation induced by mustard oil.