Somatotopic and laminar organization of fos‐like immunoreactivity in the medullary and upper cervical dorsal horn induced by noxious facial stimulation in the rat

Abstract

The distribution of fos-like-immunoreactivity (fos-LI) in the medullary and upper cervical dorsal horn was examined following noxious facial stimulation, in order to evaluate the use of fos as a marker for neuronal activation in trigeminal nociceptive pathways. Control animals that received urethane anesthesia and no facial stimulation showed substantial bilateral labeling in the trigeminal complex that was restricted to one rostrocaudal level, at the transition between the medullary dorsal horn (nucleus caudalis) and nucleus interpolaris. Noxious mechanical stimulation (pinch) of different facial sites produced labeling in the ipsilateral dorsal horn whose distribution varied predictably with the rostrocaudal and dorsoventral position of the facial stimulation site, such that rostral facial sites were represented rostrally in the dorsal horn and dorsal sites were represented ventrolaterally. The cornea was exceptional among the facial stimulation sites in that it had a specific representation at two distinct rostrocaudal levels, in C1 and the interpolaris-caudalis transition region; the position of the rostral peak was somatotopically inappropriate, based on the representation of other facial sites. The proportion of labelling in laminae III-IV relative to laminae I-II was higher with noxious mechanical stimulation than with noxious thermal (55 degrees C) or chemical (subcutaneous injection of capsaicin) stimulation. The proportion of labelling in laminae III-IV produced by electrical stimulation of the infraorbital nerve was no greater than that produced by pinch. The results suggest that fos-LI mapping can be a useful method for the investigation of somatotopy but is subject to serious limitations when used for the investigation of laminar organization. The results also suggest that the interpolaris-caudalis transition region may have properties that are distinct from those of the rest of the trigeminal complex, possibly related to an involvement in autonomic function.

A comparative assessment of two kynurenic acid analogs in the formalin model of trigeminal activation: a behavioral, immunohistochemical and pharmacokinetic study

“…The whisker pad area (Strassman and Vos, 1993)). Besides the observed significant differences, the effects of the treatment are well demonstrated by the curves in Figure 6.…”

Interactions Between Glutamate Receptors and TRPV1 Involved in Nociceptive Processing at Peripheral Endings of Primary Afferent Fibers

“…c-Fos is rapidly and transiently induced in cells of the spinal dorsal horn after noxious stimulation (Hunt et al, 1987, Strassman and Vos, 1993, Takemura et al, 2000, cFos has been widely used as a marker for analyzing nociceptive processing.…”

The Role of 5-Hydroxytryptamine3 Receptors in the Vagal Afferent Activation-Induced Inhibition of the First Cervical Dorsal Horn Spinal Neurons Projected from Tooth Pulp in the Rat

“…Iontophoretic application of ICS 205-930 (40 nA) or bicuculline (40 nA) significantly attenuated the VA stimulation-induced inhibition of glutamate iontophoretic application (60 nA)-evoked C 1 spinal neuron excitation. These results suggest that VA stimulation-induced suppression of C 1 spinal neuron activity, responding to TP stimulation, involve 5-HT 3 receptor activation, possibly originating in the descending serotonergic inhibitory system, and postsynaptic modulation of inhibitory GABAergic neurons.The trigeminal spinal nucleus is considered to be closely associated with the perception and transmission of orofacial sensory information, including nociceptive signals from tooth pulp (TP) (Strassman and Vos, 1993;Iwata et al, 1998). The trigeminal spinal nucleus is functionally and anatomically subdivided into three nuclei: oralis, interpolaris, and caudalis (Sessle, 1987).…”

“…The trigeminal spinal nucleus is considered to be closely associated with the perception and transmission of orofacial sensory information, including nociceptive signals from tooth pulp (TP) (Strassman and Vos, 1993;Iwata et al, 1998). The trigeminal spinal nucleus is functionally and anatomically subdivided into three nuclei: oralis, interpolaris, and caudalis (Sessle, 1987).…”