Effects of acupuncture on c-Fos expression in brain after noxious tooth stimulation of the rat.
Clinically, acupuncture therapy is useful for the control of acute or chronic pain. This study was designed to elucidate the antinociceptive mechanism of acupuncture and the mechanisms underlying cardiovascular reflex elicited by toothache. Expression of c-Fos, a neuronal activation marker, and the phenylethanalamine-N-methyltransferase (PNMT) were examined 1.5 hours after noxious intrapulpal tooth stimulation. Manual acupuncture was performed 20 min before noxious intrapulpal stimulation by 2 M KCl injection into upper or lower anterior tooth pulp. The acupuncture points were Li4 (Hegu) between the 1st and 2nd metacarpal bones or St36 (Zusanli) between the anterior crest of the tibial tuberosity and the fibula head below the patella. After noxious intrapulpal tooth stimulation, Fos-immunoreactive (IR) neurons were identified in the trigeminal subnucleus caudalis (Vc) and the transitional region between the subnucleus caudalis and the subnucleus interpolaris (Vi), in the inferior olivory nucleus (IO) connecting the cerebellum and other brain regions, and also the thalamic ventral posteromedial (VPM) nucleus and centrolateral (CL) nucleus, respectively. In addition, Fos-IR neurons were found in the central cardiovasuclar regulation centers, such as the hypothalamus supraoptic nucleus (SON) and paraventricular nucleus (PVN), and nucleus tractus solitarius (NTS) and rostral ventromedulla (RVLM). All acupuncture at St36 or Li4 significantly suppressed Fos-IR neurons in all Fos-expressed brain areas except the IO nucleus and attenuated the increases in arterial blood pressure (BP) and heart rate (HR) after noxious intrapulpal stimulation. Its Fos-suppressive effects were mostly blocked by naloxone, an opioid antagonist. In addition, acupuncture at St36 or Li4 significantly decreased Fos-containing PNMT, and this effect was also reversed by naloxone. These results suggest that: 1) tooth pulpal noxious signals transmit to the Vc and Vc/Vi transitional region and the 2nd afferent neuron synapse in the thalamic VPM and CL, 2) tooth pulpal pain elicits cardiovascular reflex mediated by NTS, VLM, hypothalamic SON and PVN, and 3) acupuncture reduces cardiovascular reflex elicited by toothache, is associated with the adrenergic system.
Jung
Ji-Yeon
JY
Department of Oral Physiology, Dental Science Research, School of Dentistry, 2nd Stage of Brain Korea 21 for School of Dentistry, Chonnam National University, Korea.
Yang
Hye-Ryung
HR
Jeong
Yeon-Jin
YJ
Vang
Mong-Sook
MS
Park
Sang-Won
SW
Oh
Won-Mann
WM
Kim
Sun-Hun
SH
Youn
Dae-Hwan
DH
Na
Chang-Su
CS
Kim
Won-Jae
WJ
D015669:Acupuncture Points; D015670:Acupuncture Therapy; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000378:metabolism*; D003782:Dental Pulp / Q000378:metabolism*; D006339:Heart Rate / Q000502:physiology; D008297:Male; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009339:Needles; D009474:Neurons / Q000378:metabolism; D009619:Nociceptors / Q000378:metabolism; D010625:Phenylethanolamine N-Methyltransferase / Q000378:metabolism; D010812:Physical Stimulation; D011189:Potassium Chloride / Q000494:pharmacology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013268:Stimulation, Chemical; D014098:Toothache / Q000517:prevention & control
D009292:Narcotic Antagonists; D016760:Proto-Oncogene Proteins c-fos; D009270:Naloxone; D011189:Potassium Chloride; D010625:Phenylethanolamine N-Methyltransferase