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Certain areas within the periaqueductal grey (PAG) have been implicated in cardiovascular regulation. The influence of excitotoxic lesions of the caudal dorsal periaqueductal grey on the baroreceptor-heart rate reflex and the cardiovascular response to air-jet stress was examined in awake Wistar-Kyoto rats. Pressor (11 +/- 2 mmHg) and tachycardic (25 +/- 4 beats/min) responses to air-jet were not influenced by the lesion. Similarly, the resting MAP and HR were unchanged. However, the gain of the baroreflex was reduced from -3.9 +/- 0.1 to -2.8 +/- 0.3 beats/min per mmHg and the upper threshold was increased from 120 +/- 5 to 135 +/- 7 mmHg in the lesioned group. These observations suggest that although the caudal dorsal PAG does not appear to exert a tonic influence on vasomotor tone or mediate the air-jet response, it may provide a facilitatory input to the baroreceptor-heart rate reflex. |
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