| pubmed-article:6291411 | pubmed:abstractText | There is presently little information on the efferent mechanisms responsible for the reflex cardiovascular activation during passive gastric distension. Therefore, 40 cats anesthetized with alpha-chloralose were studied with passive gastric balloon distention before and during 1) two repeated gastric distensions, 2) beta-adrenergic blockade with propranolol, 3) alpha-adrenergic blockade with phentolamine, or 4) bilateral adrenalectomy. Before and during each distension mean arterial pressure, heart rate, cardiac output, rate of rise of left ventricular pressure (dP/dt) at 40 mmHg developed pressure and calculated systemic vascular resistance were determined. Repeated gastric distension caused similar hemodynamic responses without tachyphylaxis. beta-Blockade significantly reduced the increase in dP/dt from 893 +/- 362 to 150 +/- 63 mmHg/s. alpha-Blockade significantly altered the changes in mean arterial pressure from 33 +/- 5.0 to -2 +/- 4.7 mmHg and systemic vascular resistance from 0.114 +/- 0.019 to 0.004 +/- 0.031 peripheral resistance units. Bilateral adrenalectomy significantly diminished the contractile response from 525 +/- 107 to 50 +/- 85 mmHg/s but did not significantly alter the pressor and vasoconstrictor responses. We conclude that, during passive gastric distension in cats, the increase in myocardial contractility is mediated by beta-adrenergic-receptor stimulation, whereas the arterial vasoconstrictor and pressor responses are mediated by alpha-adrenergic receptor stimulation. Additionally, during gastric distension a substantial portion of the contractile response is dependent on the integrity of the adrenal glands. | lld:pubmed |
