A Trigeminoreticular Pathway: Implications in Pain

摘要: Neurons in the caudalmost ventrolateral medulla (cmVLM) respond to noxious stimulation. We previously have shown most efferent projections from this locus project areas implicated either processing or modulation of pain. Here we show cmVLM rat receives superficial laminae medullary dorsal horn (MDH) and has neurons activated with capsaicin injections into temporalis muscle. Injections biotinylated dextran amine (BDA) MDH fluorogold (FG)/fluorescent microbeads showed lamina I II cmVLM. Morphometric analysis retrogradely-labeled were small (area 88.7 µm2±3.4) mostly fusiform shape. (20–50 µl) 0.5% muscle subsequent immunohistochemistry for c-Fos nuclei labeled dorsomedial trigeminocervical complex (TCC), cmVLM, lateral medulla, internal subnucleus parabrachial (PBil). Additional labeling was seen interpolaris spinal trigeminal nucleus, rostral superior salivatory ventromedial A1, A5, A7 subcoeruleus catecholamine areas. FG PBil produced robust label while BDA PBil. Immunohistochemical experiments antibodies against substance P, P receptor (NK1), calcitonin gene regulating peptide, leucine enkephalin, VRL1 (TPRV2) receptors neuropeptide Y that these peptides/receptors densely stained suggest MDH- projection is important pain head neck offer a potential new pathway deep via TCC, propose compose trigeminoreticular pathway, possibly homologue spinoreticulothalamic pathway.