Anti-nociceptive mechanism of baicalin involved in intervention of TRPV1 in DRG neurons in vitro.
BACKGROUND
Scutellaria baicalensis Georgi (Lamiaceae) is often included as an ingredient in traditional Chinese compound prescriptions for the treatment of fever-related or inflammatory conditions.


OBJECTIVE
The present work was to further uncover the analgesic mechanisms of baicalin (a known principal constituent of Scutellaria baicalensis) by investigating its effects on the expression of TRPV1 mRNA as well as on its functions as mediators of calcium entrance into the cytoplasm of dorsal root ganglion (DRG) neurons in vitro.


METHODS
By using CPT as an agent to eliminate the non-neuronal cells and using serum-free neurobasal as culture medium, primary cultures of rat DRG neurons with high purity and viability were established. On this basis, effects of baicalin on both the expression of TRPV1 mRNA and on the function of TRPV1 in vitro under two various temperature conditions were studied. The TRPV1 mRNA expression levels were examined by using qRT-PCR and analyzed by the method of 2(-DeltaDeltaCT). The elevation amplitudes of intracellular [Ca(2+)]i evoked by TRPV1 agonist capsaicin in DRG neurons were examined by the calcium fluorescence imaging method under confocal microscopy.


RESULTS
Baicalin was shown to down-regulate the mRNA expression levels of TRPV1 at both 37 and 39 degrees C, and under the latter temperature, the intracellular fluorescent intensity evoked by capsaicin was significantly decreased following incubation with baicalin in vitro. We also demonstrated that the actions of baicalin to TRPV1 were not achieved through pathways of TRPA1 or TRPV subfamily members.


CONCLUSIONS
Collectively, these results provide compelling evidence that the down-regulated actions of baicalin to TRPV1 in DRG neurons might account for part of the anti-nociceptive mechanism of baicalin.
Sui
Feng
F
Tang Center for Herbal Medicine Research, Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China. suifeng2136@126.com
Zhang
Chang-Bin
CB
Yang
Na
N
Li
Lan-Fang
LF
Guo
Shu-Ying
SY
Huo
Hai-Ru
HR
Jiang
Ting-Liang
TL
D000818:Animals; D000831:Animals, Newborn; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000302:isolation & purification / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002211:Capsaicin / Q000494:pharmacology; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D015536:Down-Regulation; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology*; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018613:Microscopy, Confocal; D015394:Molecular Structure; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D031364:Scutellaria baicalensis / Q000737:chemistry; D050916:TRPV Cation Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000096:biosynthesis*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D016895:Culture Media, Serum-Free; D005419:Flavonoids; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; C038044:baicalin; D002211:Capsaicin; D002118:Calcium