Descending modulation of visceral nociceptive transmission from the locus coeruleus/subcoeruleus in the rat.
The purpose of the present investigation was to examine whether electrical stimulation in the locus coeruleus/subcoeruleus (LC/SC) could modulate visceral pain evoked by noxious colorectal distention (CRD). Experiments were performed on 40 pentobarbital anesthetized male Sprague-Dawley rats. Extracellular potentials of single L(6)-S(2) spinal neuron were recorded with a carbon filament electrode. CRD (80 mmHg) was produced by inflating a balloon inside the descending colon and rectum. Electrical stimulation of the LC/SC (30, 50 and 70 microA, 100 Hz, 0.1 ms pulses) was delivered either ipsilaterally or contralaterally. Results showed that for 42/62 (68%) short-latency abrupt (SL-A) neurons, all of the short-latency sustained (SL-S) and long-latency (LL) neurons, LC/SC stimulation produced intensity-dependent attenuation of the CRD-evoked discharge. For 10/62 (16%) SL-A neurons, 6/8 (75%) inhibited (INHIB) neurons LC/SC stimulation increased the evoked discharge, for 10/62 (16%) SL-A neurons and 2/8 (25%) INHIB neurons, the evoked discharges were unaffected by the LC/SC stimulation. LC/SC stimulation also had different effects on the spontaneous activities of these neurons. The effects of LC/SC stimulation were the same both ipsilaterally and contralaterally either for the evoked discharges or for spontaneous activities. Following LC/SC lesions, LC/SC stimulation did not inhibit nociceptive responses, whereas inhibitory effects were observed by stimulation of the intact LC/SC contralateral to the recording site. These data suggest that the transmission of visceral pain was under the control of the centrifugal pathways from the LC/SC.
Liu
Limin
L
Department of Physiology, Showa University School of Dentistry, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Tsuruoka
Masayoshi
M
Maeda
Masako
M
Hayashi
Bunsho
B
Wang
Xiaomin
X
Inoue
Tomio
T
D000818:Animals; D003106:Colon / Q000294:innervation / Q000503:physiopathology; D004558:Electric Stimulation; D004594:Electrophysiology; D005071:Evoked Potentials / Q000187:drug effects; D006993:Hypnotics and Sedatives / Q000008:administration & dosage / Q000494:pharmacology; D008125:Locus Coeruleus / Q000166:cytology / Q000502:physiology*; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D010147:Pain Measurement; D010424:Pentobarbital / Q000008:administration & dosage / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time; D012007:Rectum / Q000294:innervation / Q000503:physiopathology; D012584:Sciatic Nerve / Q000502:physiology; D013116:Spinal Cord / Q000166:cytology / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D006993:Hypnotics and Sedatives; D010424:Pentobarbital