Abstract
PACAP and VIP are members of the VIP/secretin/glucagon family of peptides with neurotransmitter, neuroprotective, and neurotrophic functions. PACAP and VIP are known to be upregulated in primary sensory neurons following nerve injury, implying that these neuropeptides could be mediators of sensory transmission in neuropathic pain states. Nerve injury at the level of the trigeminal root is thought to be the prime cause of trigeminal neuralgia. Since cross-excitation (a chemically-mediated form of nonsynaptic transmission) within the TG is postulated to play a central role in trigeminal neuralgia, we studied the expression of PACAP and VIP receptors in the TG by RT PCR and immunocytochemistry. Of the three known receptors (PAC1, VPAC1 and VPAC2), RT PCR revealed the presence of mRNA for VPAC2 and several splice variants of the PAC1 receptor. Immunocytochemistry showed PAC1 and VPAC2 to be present in small-diameter TG neurons. Thus, PACAP and VIP are potential mediators of cross-excitation in the TG.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Afferent Pathways / metabolism
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Afferent Pathways / physiopathology
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Alternative Splicing / genetics
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Animals
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Cell Communication / genetics
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Cells, Cultured
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Immunohistochemistry
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Male
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Neurons, Afferent / metabolism*
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Neuropeptides / metabolism*
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Nociceptors / metabolism
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Protein Isoforms / genetics
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RNA, Messenger / metabolism
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Rats
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Rats, Sprague-Dawley
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
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Receptors, Pituitary Hormone / genetics*
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Receptors, Pituitary Hormone / metabolism
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Receptors, Vasoactive Intestinal Peptide / genetics*
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Receptors, Vasoactive Intestinal Peptide / metabolism
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Receptors, Vasoactive Intestinal Peptide, Type II
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Receptors, Vasoactive Intestinal Polypeptide, Type I
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Signal Transduction / genetics
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Trigeminal Ganglion / metabolism*
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Trigeminal Ganglion / physiopathology
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Trigeminal Neuralgia / genetics
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Trigeminal Neuralgia / metabolism*
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Trigeminal Neuralgia / physiopathology
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Vasoactive Intestinal Peptide / metabolism*
Substances
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Adcyap1 protein, rat
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Adcyap1r1 protein, rat
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Neuropeptides
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Pituitary Adenylate Cyclase-Activating Polypeptide
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Protein Isoforms
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RNA, Messenger
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide
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Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I
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Receptors, Pituitary Hormone
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Receptors, Vasoactive Intestinal Peptide
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Receptors, Vasoactive Intestinal Peptide, Type II
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Receptors, Vasoactive Intestinal Polypeptide, Type I
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Vipr1 protein, rat
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Vipr2 protein, rat
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Vasoactive Intestinal Peptide