The cardiovascular and endocrine responses to voluntary and forced diving in trained and untrained rats.
Abstract
The mammalian diving response, consisting of apnea, bradycardia, and increased total peripheral resistance, can be modified by conscious awareness, fear, and anticipation. We wondered whether swim and dive training in rats would 1) affect the magnitude of the cardiovascular responses during voluntary and forced diving, and 2) whether this training would reduce or eliminate any stress due to diving. Results indicate Sprague-Dawley rats have a substantial diving response. Immediately upon submersion, heart rate (HR) decreased by 78%, from 453 +/- 12 to 101 +/- 8 beats per minute (bpm), and mean arterial pressure (MAP) decreased 25%, from 143 +/- 1 to 107 +/- 5 mmHg. Approximately 4.5 s after submergence, MAP had increased to a maximum 174 +/- 3 mmHg. Blood corticosterone levels indicate trained rats find diving no more stressful than being held by a human, while untrained rats find swimming and diving very stressful. Forced diving is stressful to both trained and untrained rats. The magnitude of bradycardia was similar during both voluntary and forced diving, while the increase in MAP was greater during forced diving. The diving response of laboratory rats, therefore, appears to be dissimilar from that of other animals, as most b...Continue Reading
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