Effects of local serotonin administration on pain and microcirculation in the human masseter muscle.
OBJECTIVE
To investigate whether exogenously administered 5-hydroxytryptamine (5-HT) at high or low concentration influences pain and microcirculation in the human masseter muscle.


METHODS
In 12 healthy female subjects, 5-HT in 2 concentrations (0.1 micromol/L and 1,000 micromol/L) and isotonic saline were injected into the masseter muscles in a randomized and balanced double-blind manner. The pain intensity after injections was recorded with Borg's rating scale, and intramuscular blood flow was monitored continuously during the experiment with a laser-Doppler technique. Nonparametric statistics were used for analyses.


RESULTS
Administration of 5-HT at 1,000 micromol/L induced significantly more pain than saline (Wilcoxon: P < .05), while there was no difference between 5-HT at 0.1 micromol/L and saline. The blood flow did not change significantly after injection of 5-HT at either concentration compared to saline. However, changes in pain intensity and blood flow were positively correlated after injection of 5-HT at 1,000 micromol/L (Spearman: P < .05).


CONCLUSIONS
Intramuscular administration of 5-HT at 1,000 micromol/L into the human masseter muscle induced pain, but 5-HT did not have any effect on local blood flow at either concentration.
Ernberg
Malin
M
Department of Clinical Oral Physiology, Institute of Odontology, Karolinska Institutet, Huddinge, Sweden. malin.ernberg@ki.se
Hedenberg-Magnusson
Britt
B
Kurita
Hiroshi
H
Kopp
Sigvard
S
D000704:Analysis of Variance; D004311:Double-Blind Method; D005157:Facial Pain / Q000188:drug therapy*; D005260:Female; D006801:Humans; D008406:Masseter Muscle / Q000098:blood supply / Q000187:drug effects*; D008833:Microcirculation / Q000187:drug effects; D008875:Middle Aged; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012701:Serotonin / Q000008:administration & dosage*; D018490:Serotonin Agents / Q000008:administration & dosage*; D018709:Statistics, Nonparametric
D018490:Serotonin Agents; D012701:Serotonin