Maturational Effects of Substance P on Respiratory Pattern in Newborn Rabbits
Primack, Scott J.
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Eleven New Zealand rabbit pups, ranging in age from six to twenty-five days were studied. The pups were reared by their does until the day of the experiment. While the rabbits were lightly anesthetized with diethyl ether, polyethelene catheters were inserted into the trachea and one carotid artery and secured by suture. The carotid artery catheter was directed retrograde to the direction of carotid blood flow, and the cephalad end of the artery was ligated. During the surgery, Xylocaine (Astra Phannaceuticals), a topical anesthetic, was injected liberally around the trachea. To avoid coagulation during the experiment, a 1:100 solution of Panheprin (Abbot Laboratories) was flushed into the carotid artery catheter. The two vagus nerves were isolated and a looped suture was placed around each nerve. Before the actual experiment began, we allowed for a thirty:minute recovery from general anesthesia. The animal was then placed in a hammock-like device, and put into a 2.5 liter plexiglass pressure plethysmograph. The box allowed the tidal volume to be measured by the calibrated pressure in the box. The temperature in the plethysmograph was maintained between 34° and 35° C by external radiant heat. The rectal temperature of the rabbit ranged from 35° to 37° C. The warmth and natural positioning quieted the pups and there appeared to be no distress from the surgical wounds. The plethysmographic pressure, previously calibrated for volume was recorded with a differential pressure transducer. All measurements were displayed on a Beckman Multichannel Recorder. An illustration of the surgery and the plethysmograph can be seen in Figure 2.