K . Ezure, I. Tanaka Brain Research 883 2000 22 –30
23
lungs to collapse to atmospheric pressure is a specially lactated Ringer’s solution with 5 glucose was intraven-
useful maneuver to examine inputs from the rapidly-adapt- ously administered when necessary. Rectal temperature
ing pulmonary stretch receptors RARs [11,17,19] but has was maintained within 36–378C using a heating lamp. End
not been adopted for classifying respiratory neurons. In the tidal CO
was monitored and maintained at 4–5 by
2
present study, we found a group of inspiratory neurons adjusting tidal volume or frequency of a respirator.
which were characteristically activated by deflation of the lungs.
2.2. Recording and experimental protocol DRG neurons were recorded extracellularly with glass
2. Materials and methods micropipettes filled with 3 M KCl saturated with Fast
Green FCF dye DC impedance, about 1.0 MV. The Experiments were conducted on 14 adult Wistar rats
recording sites were marked with the dye. After fixation, 260–425 g. All experimental procedures were performed
serial frozen sections of the brainstem 100 mm thick in in accordance with the Guiding Principles for the Care
the frontal plane were made and stained with cresyl violet. and Use of Animals in the Field of Physiological Science
At the beginning of each experiment, we estimated the Physiological Society of Japan, 1988
. The experiments thresholds for orthodromic activation of the second-order
were reviewed and approved by the Animal Experiment relay neurons from SARs P-cells by vagal nerve stimula-
Committee of the Tokyo Metropolitan Institute for Neuro- tion. For this purpose we sampled at least five P-cells on
science. each side and measured their thresholds: these thresholds
Almost all the experimental procedures, such as surgery, for P-cells are about the same as or a little higher than
care of animals, vagal nerve stimulation, electrodes, neural those for the second-order relay neurons from RARs
recording, antidromic stimulation, or histological recon- RAR-cells see Refs. [16,17]. Stimulus intensity less
struction of the brainstem, were the same as those de- than two times the mean threshold normally less than 10
scribed previously [17,18,25,26], and are described here mA of P-cells was routinely used for vagal nerve stimula-
only briefly. tion.
The means of generating maintained lung inflation and 2.1. Surgical procedures
deflation were fully described previously [17,18]. Signals microelectrode potentials, phrenic nerve discharge, trache-
The rats were initially anesthetized with sodium pen- al pressure and blood pressure were stored on magnetic
tobarbitone Nembutal, 70 mg kg; i.p.; supplementary tape DAT recorder: PC-216A, Sony Precision Technolo-
doses about 5 mg kg per h; i.v. were given during gy, Tokyo; sampling rate 50 ms.
surgery and recording as necessary. The trachea was intubated, and cannulae placed in the femoral artery to
monitor blood pressure and in the femoral vein for drug
3. Results
