Possible Interaction: Capsaicin and Nerve Growth Factor

“In situ hybridization histochemistry (ISH) … at day 8 after the capsaicin treatment GAP-43 expression was significantly increased in small … cells as compared to control animals, and treatment with NGF in capsaicinized rats lead to an even more pronounced increase … GAP-43 expression in the small-sized cell population.”

“ NGF acutely conditions the response to capsaicin , suggesting that NGF may be important in sensitizing the response of sensory neurons to heat (a process that is thought to operate via the capsaicin receptor VR1).”

“ CAPS tachyphylaxis lowered signal intensity by ~60% but was largely prevented by NGF.”

“Increasing CAPS from 1 to 10 μM nearly doubled the number of cells activated but only modestly increased the amount co-activated by NGF.”

“ NGF elevated [Ca2+]i in about one-third of the neurons stimulated by 1 μM CAPS , whether applied before or after the latter.”

“ NGF increased capsaicin current amplitude from 144 (42) to 840 (132) pA (P<0.05), which was blocked by the TRPV1 antagonist 5'-iodoresiniferatoxin.”

“We found that CB1, NGF receptor tyrosine kinase A (trkA), and TRPV1 are … in cultured adult mouse small- to medium-sized afferent neurons and treatment with NGF (100ng/ml) for 30 min significantly increased … number of neurons that responded to capsaicin (as indicated by increased intracellular Ca(2 +) concentration).”

“The ocular effects of capsaicin treatment were associated with an NGF pathway alteration.”

“The elevation of SP mRNA, VR1 mRNA, and VR1 protein promoted by NGF and/or butyrate may be associated with increases of SP release evoked by capsaicin.”

“Furthermore, when NGF was infused in the hindlimb muscles of healthy rats (72 h using an osmotic minipump), the magnitude of the DRG neuron response to capsaicin was augmented (5.4 +/- 0.54 nA with NGF infusion vs. 3.0 +/- 0.17 nA in control; P < 0.05).”

“With the addition of NGF in the culture dish containing the DRG neurons, the magnitude of the DRG neuron response to capsaicin was greater (6.4 +/- 0.27 nA; P < 0.05 vs. control) than that seen in control (2.9 +/- 0.16 nA).”

“The present study demonstrates that a capsaicin impairment of small diameter primary sensory neurons followed by an NGF treatment evokes a characteristic pattern of ERK and STAT3 activation indicative of neuronal degeneration and regeneration.”

“… intraplantar nerve growth factor (NGF) injection at … h after the capsaicin treatment, and collection of tissues 4 h later, markedly increased the level of phospho-ERK in the sciatic nerve … DRG, as compared to the samples taken from rats at the same time points with a capsaicin treatment only.”

“The results show that topical administration of capsaicin causes a primarily NK1 receptor‐dependent increase in the NGF content of rat skin, which is susceptible to inhibition by beta adrenergic agonists.”

“Topical capsaicin (>1 mg/ml ethanol) caused a concentration‐ and time‐dependent increase in the concentration of NGF in rat skin.”