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Origin, distribution, and morphology of galaninergic fibers in the rodent trigeminal system
Journal article   Open access   Peer reviewed

Origin, distribution, and morphology of galaninergic fibers in the rodent trigeminal system

K L Simpson, B D Waterhouse and R C Lin
Journal of comparative neurology (1911), v 411(3), pp 524-534
30 Aug 1999
DOI: https://doi.org/10.1002/(SICI)1096-9861(19990830)411:3<524::AID-CNE13>3.0.CO;2-X
PMID: 10413784
Featured in Collection :   UN Sustainable Development Goals @ Drexel
url
https://doi.org/10.1002/(sici)1096-9861(19990830)411:3<524::aid-cne13>3.0.co;2-xView
Published, Version of Record (VoR)Maybe Open Access (Publisher Bronze),  Open
url
https://doi.org/10.1002/(SICI)1096-9861(19990830)411:3<524::AID-CNE13>3.0.CO;2-XView
Published, Version of Record (VoR) Open

Abstract

Afferent Pathways - chemistry Afferent Pathways - ultrastructure Animals Dopamine beta-Hydroxylase - analysis Female Galanin - analysis Microscopy, Fluorescence Nerve Tissue Proteins - analysis Rats Synapses - chemistry Thalamus - chemistry Trigeminal Nerve - chemistry Trigeminal Nuclei - chemistry
The neuropeptide galanin (Gal) is found throughout the central nervous system. Of particular interest is the fact that Gal is present within the majority of noradrenergic locus coeruleus (LC) neurons. However, very few, if any, Gal-immunoreactive fibers have been identified in many of the major efferent targets of LC, including sensory neocortex and dorsal thalamus. The goal of the present study was to examine the Gal fiber innervation of the rodent trigeminal somatosensory system and its connection to the LC. Our results show that at least two different morphological profiles of Gal-immunoreactive fibers are present within relay nuclei along the ascending trigeminal pathway. Numerous small caliber Gal-immunoreactive fibers with bouton-like swellings were noted within the barrel cortex, the ventroposterior medial (VPM) nucleus, the posterior medial (POm) nucleus, the zona incerta (ZI), the reticular nucleus (nRT) of the thalamus, and the principal (PrV) and spinal (SpV) nuclei of the trigeminal complex. Immunoreactive fibers were prevalent in, but not restricted to, layer I of the barrel cortex. Within the somatosensory thalamus, the density of Gal-immunoreactive fibers was higher in POm than in VPM. Laminae I and II of SpV and the nRT and ZI also contained dense, large-diameter Gal-immunoreactive fibers. These large-diameter Gal-immunoreactive fibers did not co-contain dopamine beta-hydroxylase (DBH). In contrast, virtually every small-caliber Gal-immunoreactive fiber colocalized with DBH. To determine whether Gal-immunoreactive fibers originated from LC, we combined immunohistochemical procedures with fluorescent tracing techniques. After retrograde tracer injections into several trigeminal relay nuclei, we observed that approximately 50% of the labeled LC neuronal population was immunoreactive for Gal. Our results suggest an extensive Gal-immunoreactive fiber innervation of the rodent trigeminal system, much of which may originate from LC neurons in the brainstem.

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Neurosciences
Zoology
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