Light and electron microscopic localization of calcitonin gene-related peptide immunoreactivity in lamina II of the feline trigeminal pars caudalis/medullary dorsal horn: a qualitative study.
Calcitonin gene-related peptide (CGRP) is a neuropeptide that is associated with a subset of primary afferent fibers and appears to have a role in nociception. The purpose of the present study was to perform a qualitative light, and especially electron microscopic (LM and EM), examination of CGRP-immunoreactivity (IR) within lamina II (substantia gelatinosa) of the feline pars caudalis/medullary dorsal horn (PC/MDH) of the spinal trigeminal nucleus. The LM investigation revealed massive CGRP-IR within lamina II outer, with fewer fibers that traversed lamina II inner. The EM preparations showed CGRP-IR in small, thinly myelinated and unmyelinated axons, preterminal axons, and in axon terminals that formed asymmetric synaptic contacts onto small dendritic profiles. The terminals with CGRP-IR were often the central element within glomeruli, where the terminal usually formed 2 or more asymmetric synaptic specializations onto 1 or more dendrites. Many of these postsynaptic dendrites contained synaptic vesicles. Other profiles were seen forming presynaptic contacts onto the terminal with CGRP-IR, and these profiles most likely represent presynaptic dendrites and/or other axon terminals of intrinsic origin. The synaptic association of terminals showing CGRP-IR with vesicle-containing dendrites, presynaptic dendrites, and/or other axon terminals suggests that terminals with CGRP-IR are especially susceptible to modulation.
Henry
M A
MA
Department of Neurological Surgery, University of Washington, Seattle 98195.
Nousek-Goebl
N A
NA
Westrum
L E
LE
D000344:Afferent Pathways / Q000166:cytology / Q000648:ultrastructure; D000818:Animals; D001369:Axons / Q000648:ultrastructure; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D002415:Cats; D003712:Dendrites / Q000648:ultrastructure; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure; D013569:Synapses / Q000648:ultrastructure; D014279:Trigeminal Nucleus, Spinal / Q000166:cytology* / Q000648:ultrastructure
D015740:Calcitonin Gene-Related Peptide