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Journal of Dental Research, Vol. 81, No. 9,
598-602 (2002)
DOI: 10.1177/154405910208100904
Effect of Serotonin (5-HT) on Trigeminal Rhythmic Activities Generated in in vitro Brainstem Block Preparations
A. Mori,
M. Kogo*,
K. Ishihama,
S. Tanaka,
A. Enomoto,
H. Koizumi and
T. Matsuya
First Department of Oral & Maxillofacial Surgery, Osaka University, Graduate School of Dentistry, 1-8 Yamadaoka, Suita, Osaka, 565-0871, Japan;
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Figure 1. Effect of 5-HT on trigeminal rhythmic activities. (A) After a coronal transection at the Y-crossing point, BIC (10 µM) - NMA (20 µM) application induced trigeminal rhythmic activities. (B) Rhythmic trigeminal motor activity was not induced in the whole brainstem preparations by chemical application of BIC (10 µM) - NMA (20 µM), whereas it was by an application of BIC (10 µM) - NMA (20 µM) combined with 5-HT (60 µM). (C) Comparison of the effect of 5-HT (60 µM) - NMA (20 µM) - BIC (10 µM) on trigeminal activities (Vm) with that on cervical nerve (C2) activities (n = 5). Middle traces show Vm and C2 activities after application. These activities were not synchronized with each other. Upper traces: trigeminal activities (Vm). Lower traces: cervical nerve (C2) activities.
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Figure 2. Effect of 5-HT agonist and antagonist in whole and medium blocks. (A) Application of 5-HT2C receptor agonist (DOI, 20 µM) and 5-HT1A receptor antagonist (NAN190, 20 µM) induced rhythmic trigeminal motor activity in the whole brainstem preparations, whereas application of the 5-HT2BC,5 receptor antagonist (methysergide, 50 µM) and 5-HT1A receptor agonist (8OH-DPAT, 50 µM) did not. (B) Application of the 5-HT2C receptor agonist (DOI, 20 µM) and 5-HT1A receptor antagonist (NAN190, 20 µM) induced rhythmic trigeminal motor activity in the brainstem preparations that contained the facial nucleus (medium block), whereas application of the 5-HT2BC,5 receptor antagonist (methysergide, 50 µM) and 5-HT1A receptor agonist (8OH-DPAT, 50 µM) did not. (C) A section that contained the facial nucleus (medium block) prepared after the end of an experiment. (Infra-red photograph of a sagittal section, 250 µ.)
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Figure 3. Cycle frequency of rhythmic trigeminal motor activities in minimum and whole blocks. (A) Rhythmic trigeminal motor activity was induced by an application of 5-HT (60 µM), 5-HT2C receptor agonist (DOI, 20 µM), 5-HT1A receptor antagonist (NAN190, 20 µM), and those in combination with BIC (10 µM) - NMA (20 µM) in whole brainstem preparations. Furthermore, it was also induced by BIC (10 µM) - NMA (20 µM) stimulation alone, whereas inhibition was not recognized in the minimum preparations. (B) Bar graphs indicate the cycle frequency of rhythmic trigeminal motor activities in the minimum and whole brainstem preparations as induced by 5-HT (60 µM) and those related agents (DOI, 20 µM; NAN190, 20 µM) with BIC (10 µM) - NMA (20 µM), respectively. Control: Cycle frequency of trigeminal rhythmic activities induced by BIC-NMA in the minimum brainstem blocks. In the whole brainstem, the rhythm induced by 5-HT and related agents was slower than in the control, whereas when these were applied to the minimum brainstem preparations, the rhythm was not significantly different from that of the control. *: significantly different from control (p < 0.01). Whole block: 5-HT (n = 9), DOI (n = 4), NAN190 (n = 6). Minimum block: Control (n = 8), 5-HT (n = 7), DOI (n = 14), NAN190 (n = 14).
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