Lc. Yang et al., KNEE-JOINT INFLAMMATION ATTENUATES SPINAL FOS EXPRESSION AFTER UNILATERAL PAW FORMALIN INJECTION IN RAT, Neuroscience letters, 225(2), 1997, pp. 89-92
Carrageenan-induced knee joint inflammation evoked a transient spinal
FOS protein expression in neurons localized in the apical region of la
minae I-III with peak activity observed 2 h after inflammation. Consis
tent with previously published observations, paw formalin injection ev
oked a distinct pattern of FOS protein expression in L3-L5 spinal segm
ents. The majority of FOS-positive neurons were localized in the super
ficial dorsal horn (laminae I-II). Laminae V and VI contained moderate
numbers of labeled neurons and only a few labeled nuclei were visible
in laminae VII-X. In contrast, ipsilateral paw formalin injection, if
administered 4 h after carrageenan-induced knee inflammation, evoked
significantly fewer FOS positive neurons in all laminar and segmental
levels analyzed as compared with formalin injected animals but without
previous knee joint inflammation. These data indicate that primary ac
ute or subacute nociceptive input may evoke central processes that are
characterized by an inducible form of central inhibition which then m
ay serve to modulate the subsequent spinal effect of superimposed noci
ceptive peripheral stimulation. (C) 1997 Elsevier Science Ireland Ltd.