Ulex europaeus Agglutinin-I Binding to Dental Primary Afferent Projections in the Spinal Trigeminal Complex Combined with Double Immunolabeling of Substance P and GABA Elements Using Peroxidase and Colloidal Gold

Abstract

Ulex europaeus agglutinin I (UEA-I) is a plant lectin with an affinity for L-fucosyl residues in the chains of lactoseries oligosaccharides associated with medium- and smaller-diameter dorsal root ganglion neurons and their axonal processes. These enter Lissauer's tract and terminate within the superficial laminae of the spinal cord overlapping projections known to have a nociceptive function. This implies that the surface coatings of neuronal membranes may have a relationship with functional modalities. The present investigation further examined this concept by studying a neuronal projection with a nociceptive function to determine whether fucosyl-lactoseries residues were incorporated in its primary afferent terminals. Transganglionic transport of horseradish peroxidase (HRP) following injection into tooth pulp chambers was employed to demonstrate dental pulp terminals in the trigeminal spinal complex, while peroxidase and fluorescent tags were used concomitantly to stain for UEA-I. Double immunolabeling for substance P (SP) and gamma-aminobutyric acid (GABA) using peroxidase and colloidal gold allowed a comparison of the distribution of a known excitatory nociceptive transmitter with that of UEA-I binding in specific subnuclei. Synaptic interrelationships between UEA-I positive dental pulp primary afferent inputs and specific inhibitory terminals were also examined. SP immunoreactivity occurred in laminae I and outer lamina II (IIo) of subnucleus caudalis (Vc) and in the ventrolateral and lateral marginal region of the caudal half of subnucleus interpolaris (Vi), including the periobex area in which Vi is slightly overlapped on its lateral aspect by cellular elements of Vc. The adjacent interstitial nucleus (IN) also showed an intense immunoreactivity for this peptide antibody. UEA-I binding displayed a similar distribution pattern in both Vc and Vi, but extended into lamina IIi and the superficial part of Lamina III in Vc. Dental pulp terminals were found to have a comparable distribution; however, many extended into the dorsal portion of the caudal half of Vi and the ventromedial quadrant of rostral Vi. Electron-microscopic analysis showed that transganglionically labeled dental pulp terminals contained ovoid, complex membrane-bound vacuoles laden with transported HRP. The preterminal axon and synaptic membranes of those dental pulp terminals located in zones of Vc and Vi displaying an affinity for UEA-I were usually characterized by a patchy, electron-dense coating of the peroxidase tag. SP was demonstrated ultrastructurally with Protein-A colloidal gold (3-nm particles), whereas GABA immunoreactivity was revealed by the avidin-biotin-peroxidase method.(ABSTRACT TRUNCATED AT 400 WORDS)

Central Connections of Trigeminal Primary Afferent Neurons: Topographical and Functional Considerations

“…These regions, which receive nociceptive specific information, also contain numerous other substances implicated in nociception and reflex modulation. Positive staining has been shown for y-aminobutyric acid-like (GABA), serotonin-like (5-HT), and enkephalin-like (Enk) immunoreactivity as well as other neuropeptides (Matthews et al, 1989). It is likely that further studies and novel approaches will continue to facilitate our understanding of structure-function relationships in the trigeminal system.…”

Effects of GABA Receptor Antagonist on Trigeminal Caudalis Nociceptive Neurons in Normal and Neonatally Capsaicin-Treated Rats

“…A GABAergic modulatory substrate also exists in the medullary dorsal horn, i.e., trigeminal subnucleus caudalis (Vc) (Almond et al 1996;Ginestal and Matute 1993;Grudt and Henderson 1998;Iliakis et al 1996;Kondo et al 1995;Matthews et al 1989), and in addition NMDA mechanisms have been shown to contribute to neuroplastic changes in the mechanoreceptive field (RF) properties of Vc nociceptive neurons and associated responses induced by nociceptive afferent inputs in intact rats (Chiang et al 1998;Yu et al 1996). Furthermore, we have recently demonstrated that NMDA-dependent neuroplastic changes in the RF properties of Vc nociceptive neurons in adult rats depleted of C-fiber afferents by neonatal treatment with capsaicin (CAP rats) (Chiang et al 1997).…”

Acute and Chronic Craniofacial Pain: Brainstem Mechanisms of Nociceptive Transmission and Neuroplasticity, and Their Clinical Correlates

“…The inhibitory neurochemical GABA appears to modulate the excitability of nociceptive neurons through its local release from interneurons which, in the VBSNC, may principally occur in the substantia gelatinosa of subnucleus caudalis (Matthews et al, 1989;DiFiglia and Aronin, 1990;Fromm et al, 1992;Ginestal and Matute, 1993;Kondo et al, 1995;Almond et al, 1996;Chiang et al, 1999;and see Dubner and Bennett, 1983;Sessle, 1987;Yaksh and Malmberg, 1994). Different subtypes of the GABA receptor have been discovered, and while the specific roles of these subtypes in the VBSNC have so far received only limited attention, they might be differentially involved in V nociceptive transmission.…”