It is well known that the vascular smooth muscle tone is regulated not only by the activity of the sympathetic nervous system, but also by the release of vasoactive factors from the endothelium including nitric oxide (NO), prostacyclin, thromboxane A2 and endothelin (1; 2; 3) that can be induced by both chemical and mechanical stimuli (4). In addition, several studies have reported endothelium-independent vasodilator responses to an unknown endogenous mediator, in rabbit and rat resistance arteries (5;6). PAF is a potent phospholipid mediator released by various cell types including platelets, leukocytes, macrophages, endothelial cells (7) and cultured rat vascular smooth muscle cells (8). This mediator has many biological actions already described (9). Several reports have demonstrated that PAF (<1 μg kg−1, i.v.) induce severe cardiovascular alterations, including a decrease in arterial blood pressure (10; 11), a direct negative chronotropic effect (12; 13) and an increase in vascular permeability (14). The hypotensive effect of PAF has been attributed mainly to the dilation of resistance vessels (15;16), thus suggesting a role for this mediator in the modulation of vascular smooth muscle tone.
KeywordsMean Arterial Pressure Systemic Vascular Resistance Carotid Artery Occlusion Carotid Occlusion Vascular Smooth Muscle Tone
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- 4.Kuo, L.I.H., Chilian, W.H., Davis, M.J. (1991). Interaction of pressure-and flow-induced responses in porcine coronary resistance vessels. Am. J. Physiol., 260, H1706 - H1715.Google Scholar
- 14.Macmanus, L.M., Hanahan, D.J., Demopoulos, C.a. and Pinckard, R.N. (1980). Pathobiology of the intravenous infusion of acetyl glyceryl ether phosphorylcholine (AGEPC), a synthetic platelet-activating factor (PAF), in the rabbit. J. Immunol., 124, 2919–2924.Google Scholar
- 20.Castro-Faria-Neto, H.C., Araújo, C.V., Moreira, S., Bozza, P.T., Thomas, G., Barbosa-Filho, J.M., Cordeiro, R.S.B. and Tibiriçâ, E. (1995): Yangambin, a new naturally-occurring platelet-activating factor receptor antagonist: in vivo pharmacological studies. Planta Medica, 61, 106–112.PubMedCrossRefGoogle Scholar
- 24.Tramposch, K.M., Chilton, F.H., Stanley, P.L., Franson, R.C, Havens, M.B., Nettleton, D.O., Davern, L.B., Darling, I.M. and Bonney, R.J. (1994). Inhibitor of phospholipase AZ blocks eicosanoid and platelet-activating factor biosynthesis and has topical anti-inflammatory activity. J. Pharmacol. Exp. Ther., 271, 852–859.PubMedGoogle Scholar