title: Role of rostral medulla in serotonin-induced changes of respiratory rhythm in newborn rat brainstem-spinal cord preparations.
abstract: Abnormalities of the serotonin (5-hydroxytryptamine, 5-HT) system may induce respiratory disorders. We examined which regions in the rostral medulla are important for the effect of 5-HT on the frequency of respiratory-like nerve (fR-like) activity by transecting the preparations at different levels near the facial nucleus (nVII) in newborn rat brainstem-spinal cord preparations. The fR-like activity at the fourth cervical ventral root (C4) of the Pons-medulla-spinal cord preparations in 2-3-day-old rats (n=25) was monitored at 26°C, and the change in fR-like activity in response to application of 10μM 5-HT before and after transection was compared among three groups, in which nVII was retained (group A, n=10), partially retained (group B, n=7), or eliminated (group C, n=8) by the transection. Before transection, the resting fR-like activity (set to 100%) and stimulant effect of 5-HT (+101-143%) were similar among the groups. After transection, resting fR-like activity increased in all groups, but the facilitatory effects of 5-HT on the fR-like activity were abolished in groups A and C (fR-like activity of -4% and +7%, respectively). In group B, 5-HT became inhibitory (fR-like activity of -28%). In conclusion, a distinct part of the rostral medulla in the absence of pontine influences may mediate the inhibitory effects of 5-HT on the respiratory rhythm.
authors: Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan. Electronic address: m-makino@tky.ndu.ac.jp.
authors: Michio
authors: M
authors: Makino
authors: Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan.
authors: Chikako
authors: C
authors: Saiki
authors: Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan.
authors: Ryoji
authors: R
authors: Ide
authors: Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan.
authors: Shigeji
authors: S
authors: Matsumoto
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001933:Brain Stem / Q000502:physiology; D008526:Medulla Oblongata / Q000502:physiology*; D009924:Organ Culture Techniques; D051381:Rats; D017208:Rats, Wistar; D012119:Respiration / Q000235:genetics; D015656:Respiratory Mechanics / Q000235:genetics; D012701:Serotonin / Q000502:physiology*; D013116:Spinal Cord / Q000502:physiology*
chemical_list: D012701:Serotonin
keywords: 5-HT; In vitro; Medulla; Neonatal rat; Pons; Respiratory rhythm