Role of endothelin-1 in the central neural cardiovascular control |
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Authors: | L N Shapoval V F Sagach L S Pobegailo L B Doloman V G Shevchuk |
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Institution: | (1) Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine;(2) Bogomolets National Medical University, Kiev, Ukraine |
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Abstract: | In acute experiments on cats, endothelin-1 (ET-1) was injected into the sympathoexcitatory neuronal structures of the ventrolateral
medulla (VLM) and the effects of injections on the peripheral mechanisms of circulation control were studied. Effects of ET-1
appeared to be dose-dependent. Injections of 200 pmol ET-1 into the structures of the tested brain zone resulted in considerable
regular hypertensive responses due to an increase in the common peripheral vascular resistance (PVR), which corresponds to
vasospasm. ET-1 in a smaller dose (100 pmol) could cause either hypertensive or, in some cases, hypotensive responses. Hemodynamic
responses induced by injections of 100 pmol ET-1 into the sites of localization of vasomotor neurons in the VLM were based
on less expressed shifts in the peripheral vascular resistance, as compared with the effects of ET-1 in the dose of 200 pmol.
The effects were related to either facilitation or suppression (in the cases of hypertensive or hypotensive responses, respectively)
of descending sympathoexcitatory influences from the VLM on different vascular pools. The threshold for excitation of vasomotor
neurons in the tested brain area is likely to be considerably lower as compared with that for medullary “cardiac” neurons,
because injections of 200 pmol ET-1 in the site of localization of cardiac neurons were followed by either enhancement, or
suppression of the contractile myocardiac activity, while the heart rate usually decreased. The effects of ET-1 were facilitated
after blocking of GABAa receptors with bicuculline and attenuated after preliminary application of GABA to the ventral surface
of the medulla. The results indicate the possibility of interaction ET-1 and GABA on the neurons in the VLM. Such interaction
is likely to be directed toward providing an optimum mode of regulation of the blood circulation. |
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