Effect of 2,4-dinitrophenol under non-oxygenated condition in pons-medulla-spinal cord preparations in newborn rats: comparison with medulla-spinal cord preparations.
We tested whether depression of respiratory frequency (fR) under non-oxygenated artificial cerebrospinal fluid (aCSF) in pons-medulla-spinal cord (PMS) and medulla-spinal cord (MS) preparations is significantly influenced by the mitochondrial uncoupler 2,4-dinitrophenol (2,4-DNP) in newborn rats. Preparations were obtained from 0- to 4-day-old rats, and fR was monitored at the C4 ventral root in environmental temperature (24 degrees C). 2,4-DNP was dissolved in aCSF (1, 10 or 30 microM; pH 7.4), and we measured fR in PMS (n=19) and MS (n=16), both of which were superfused with aCSF equilibrated with oxygenated (95% O2-5% CO2) or non-oxygenated (10% O2-5% CO2, balanced with pure N2) gas. Our results showed that: (1) fR was significantly lower in PMS than MS, (2) fR was significantly decreased under non-oxygenated aCSF in both PMS and MS and (3) fR under non-oxygenated aCSF was significantly increased by 2,4-DNP applications at 10 and 30 microM in PMS but not in MS. Our results suggest that depression in fR under non-oxygenated aCSF in PMS and MS may not be due simply to O2 limitation, and 2,4-DNP has a stimulant effect on the medullary respiratory rhythm generator (RRG) through pontine RRG regulatory mechanisms under non-oxygenated aCSF.
Saiki
Chikako
C
Department of Physiology, Nippon Dental University, School of Life Dentistry at Tokyo, 1-9-20 Fujimi, Chiyoda-ku, Tokyo 102-8159, Japan. chikako@tky.ndu.ac.jp
Makino
Masaya
M
Matsumoto
Shigeji
S
D019297:2,4-Dinitrophenol / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008526:Medulla Oblongata / Q000187:drug effects*; D010100:Oxygen / Q000494:pharmacology*; D011149:Pons / Q000187:drug effects*; D051381:Rats; D012119:Respiration / Q000187:drug effects; D013116:Spinal Cord / Q000187:drug effects*; D014475:Uncoupling Agents / Q000494:pharmacology*
D014475:Uncoupling Agents; D019297:2,4-Dinitrophenol; D010100:Oxygen