Inflammation-induced changes in primary afferent-evoked release of substance P within trigeminal ganglia in vivo.
Substance P (SP) is synthesized in a subset of nociceptive sensory neurons and is released from their peripheral and central terminals. Here we demonstrate with the use of in vivo microdialysis and radioimmunoassay techniques that SP is also released within trigeminal ganglia following intraganglionic application of KCl, veratridine or capsaicin, and after electrical stimulation of peripheral afferent fibers. Both the basal and KCl-evoked release of SP are shown to be dependent on extracellular calcium. Using the turpentine-induced model of unilateral orofacial inflammation we also show that both the basal and KCl-evoked release of SP within trigeminal ganglia are greatly increased on the inflamed side 48 h after induction of inflammation. Coupled with previous demonstrations of excitatory effects of SP on sensory neurons, these results suggest that SP fulfils the role of a non-synaptically released diffusible chemical messenger that may modulate the somatic excitability of neurons within sensory ganglia in inflammatory pain states.
Neubert
J K
JK
Division of Oral Biology and Medicine, UCLA School of Dentistry, 90095-1668, Los Angeles, CA, USA.
Maidment
N T
NT
Matsuka
Y
Y
Adelson
D W
DW
Kruger
L
L
Spigelman
I
I
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology; D002450:Cell Communication / Q000502:physiology; D004558:Electric Stimulation; D006168:Guinea Pigs; D007249:Inflammation / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009475:Neurons, Afferent / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009619:Nociceptors / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology; D017288:Pain Threshold / Q000187:drug effects / Q000502:physiology; D013373:Substance P / Q000378:metabolism* / Q000494:pharmacology; D012668:Trigeminal Ganglion / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology*
D013373:Substance P; D002211:Capsaicin; D002118:Calcium