VASOCONSTRICTION DURING COLD PRESSOR TEST--ALPHA ADRENERGIC BLOCKADE

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Over the last 3 years since the study has begun we have completed the portion of the study addressing alpha-antagonists and the response to the cold pressor test. The data show that the peripheral vasoconstriction response is attenuated by phentolamine. These results have been previously published (in 1994) and were included in last years GCRC report. The GCRC grant was acknowledged in these abtracts and papers. The other aim in this study was to assess the effects of alpha- adrenergic antagonism on the vasomotor and metabolic mechanisms that maintain norniothermia in the absence of cold stress. These studies were also completed and were published in abstract as well as manuscript form. The findings indicate that alpha-antagonists decrease vasomotor tone, increase heat loss through the skin, which results in a lower core temperature. There is also a dose-response that we have shown for these effects. One additional area of interest was that of heart rate variability. Working with Lee Fleisher in the Dept. of Anesthesiology, we were able to describe the effects of core hypothermia on changes in heart rate variability in human subjects. We showed increased low frequency power in the spectral analysis for R to R interval variability.