[Effects of microiontophoretically applied flurazepam on the respiratory units in the region of the nucleus parabrachialis of the rabbit].
Experiments were carried out on 36 urethane-chloralose aneasthesized, paralyzed, vagotomized and artificially ventilated rabbits. Five-barrel glass micropipettes were used to record unit discharges and to apply flurazepam iontophoretically in the region of the nucleus parabrachialis. Inspiratory units (IUs), expiratory units (EUs), phase-spanning units (I-EUs and E-IUs) and non-respiratory units (NRUs) were observed. 26 (55.3%) out of 47 IUs, 17 (94.4%) out of 18 EUs, 11 (91.7%) out of 12 I-EUs, 2 (18.1%) out of 11 E-IUs and 43 (60.6%) out of 71 NRUs were depressed by flurazepam. The depressant ratio of EUs and I-EUs was statistically different from that of IUs and E-IUs respectively. In flurazepam sensitive 5 IUs and 2 EUs, the depressant effect could not be antagonized by GABA-A receptor antagonist bicuculline. In 10 flurazepam sensitive NRUs, there were 6 (60%) units whose depressant effect of flurazepam could be antagonized by bicuculline. In addition, the effects of acetylcholine (ACh) on the respiratory units and NRUs were examined, 15 (75%) out of 20 IUs were excited and the remaining units were not influenced. The effects of ACh on the EUs, I-EUs and E-IUs were variable, but the effects of ACh on the NRUs were mainly excitatory. In 5 IUs and 1 phase-spanning respiratory units, the depressant effect of flurazepam could not be antagonized by ACh. The results showed that flurazepam mainly depressed the EUs and I-EUs in the region of nucleus parabrachialis, thus interfering with the normal phase transition between the inspiratory and expiratory phase and reducing the respiratory rate.(ABSTRACT TRUNCATED AT 250 WORDS)
Yu
B J
BJ
Xu
N S
NS
Zhang
J R
JR
D000818:Animals; D004594:Electrophysiology; D005260:Female; D005479:Flurazepam / Q000494:pharmacology*; D007478:Iontophoresis / Q000379:methods; D008297:Male; D011149:Pons / Q000502:physiology*; D011817:Rabbits; D012119:Respiration / Q000187:drug effects*; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid; D005479:Flurazepam