In order to investigate the involvement of
glutamate receptor systems in
allodynia induced by
prostaglandin (PG) E2 or F2 alpha, we co-administered antagonists for
N-methyl-D-aspartate (
NMDA), non-
NMDA, or
metabotropic glutamate receptors intrathecally with
PGE2 or
PGF2 alpha and examined their effects on the
allodynia evoked in conscious mice by non-noxious brushing of the flanks.
MK-801, a non-competitive
NMDA receptor channel blocker, and D-AP-5, a selective
NMDA receptor antagonist, dose-dependently blocked PGE2-induced
allodynia with an IC50 of 1.60 and 0.52 microgram/mouse, respectively. A
glycine binding-site antagonist for the
NMDA receptor, 7-Cl-KYNA, did not influence it. None of these
NMDA receptor antagonists inhibited
PGF2 alpha-evoked
allodynia. Non-
NMDA receptor antagonists
GAMS and
CNQX inhibited both PGE2- and
PGF2 alpha-induced
allodynia. On the other hand, L-AP-3 and L-AP-4, putative
metabotropic glutamate receptor antagonists, dose-dependently antagonized the
allodynia induced by
PGF2 alpha with an IC50 of 0.92 and 3.26 ng/mouse, respectively, but not that induced by
PGE2. Intrathecal administration of
L-glutamate produced
allodynia over a wide range of low doses from 0.1 pg to 0.1 microgram/mouse, and the maximal effect was observed at 1 ng. Similar to
allodynia induced by
prostaglandins, the response lasted over a 50-min experimental period. These results demonstrate that both PGE2- and
PGF2 alpha-evoked
allodynia are mediated through a pathway that includes the
glutamate receptor system but that subtypes of
glutamate receptors involved and sites of action in the spinal cord may be different between them.