M. Takemura et al., Mapping of c-Fos in the trigeminal sensory nucleus following high- and low-intensity afferent stimulation in the rat, EXP BRAIN R, 130(2), 2000, pp. 113-123
Although previous studies have suggested that nociceptive afferents from in
tra-oral and facial structures are organized differently in the trigeminal
sensory nucleus (TSN), more detailed data are needed. The present study aim
ed to fill this gap, by examining the changes in the expression of c-Fos wi
thin the rat TSN following high- and low-intensity electrical stimulation a
pplied to the Gasserian ganglion (GG). A low-intensity stimulus (0.1 mA) in
duced c-Fos in many neurons in the dorsomedial subdivision (Vodm) of the or
al subnucleus (Vo; mean+/-SEM in a certain segment=163.0+/-42.7), in the me
dial part of the dorsomedial subdivision (Vidm) of the interpolar subnucleu
s (Vi; 120.5+/-40.1), in the medial corner of the magnocellular zone (VcIII
/IV; 47.5+/-10.5), and in the superficial layers (VcI/II; 1330.0+/-65.6) al
ong the entire length of the dorsomedial-ventrolateral axis of the caudal s
ubnucleus (Vc). A modest number of Fos-positive neurons were induced in the
dorsal principal subnucleus (Vp; 10.0+/-4.9) and in the lateral VcIIL/IV (
11.5+/-1.6). A high-intensity stimulus (1.0 mA) significantly increased the
number of Fos-positive neurons in each subdivision compared with the low-i
ntensity stimulus (Vp 32.3+/-10.8; Vodm 270.3+/-75.3; Vidm 189.3+/-38.5; me
dial VcIII/IV 77.5+/-18.2; lateral VcIII/IV 24.8+/-9.3; VcI/II, 2155.8+/-47
0.2). At both low- and high-intensity stimulation, the fields where Fos-pos
itive neurons appeared are restricted to the dorsal or dorsomedial subdivis
ions of the rostral subnuclei, Vp, Vo and Vi, where the main projectional f
ields of primary afferents from the intraoral structures are found, while F
os-positive neurons were distributed in the entire VcI/II, along the dorsom
edial-ventrolateral axis of Vc, where the main projectional fields of prima
ry afferents from the facial skin are found. The threshold to induce c-Fos
is, however, different according to the fields. These results suggest that
nociceptive processing in the intra-oral region is mediated through the ent
ire length of the rostrocaudal axis of TSN, but is mediated primarily throu
gh VcI/II in the facial region.