Vascular system histamine effects

Cardiovascular effects Harmala alkaloids have cardiovascular effects (Aarons et al. 1977). Harmine, harmaline, and harmalol decrease heart rate, but increase pulse pressure, peak aortic flow, and myocardial contractile force in dogs. Harmine reduces systemic arterial blood pressure and peripheral vascular resistance. Vascular resistance effects are not mediated by jS-adrenergic or histamine HI receptors. 

The opioids are considered relahvely safe from a cardiovascular standpoint. Myocardial depression is minimal. Changes in heart rate are species dependent and usually manifest as a mild decrease in heart rate however, a significant increase in heart rate can be seen in horses, which is consistent with the central excitatory effect that often occurs. Opioids inhibit the baroreceptor reflex response to changes in blood pressure. Certain opioids may cause systemic vasodilatation, decreased peripheral vascular resistance and hypotension secondary to histamine release. Morphine and meperidine (pethidine) are the opioids most likely associated with this effect. This is typically seen after rapid i.v. administration, is dose dependent and does not result from mast cell... 

A comprehensive review of histamine receptors in the cardiovascular system has Ijeen published. Histamine lowers blood pressure by causing widespread vasodilatation in most animal species but the effects are complex to analyse. It is clear that both H and H2 receptors are involved, but their distribution and effect varies depending on the species and particular vascular bed under study. Both types of antagonist have to be administered together to fully block many of the vascular effects of... 

In 1907 Windaus and Vogt completed the first chemical synthesis of histamine and soon after Sir Henry Dale and coworkers began investigations that showed that histamine was a powerful vasodepressant, it stimulated smooth muscle from the gut and respiratory tract and caused shock when injected into laboratory animals mimicking the systemic effects of anaphylaxis. These early results were followed by demonstration of the involvement of histamine in vascular reactions of the skin and the observation that morphine caused the so-called triple response in human skin, that is, the event sequence of an initial red spot followed by a red irregular flare and a fluid-filled wheal. Over 30 years later antihistamines were shown to reduce morphine-induced skin wheals, and histamine itself was detected in effluents of isolated perfused cat gastrocnemius muscle after arterial injection of opium alkaloids. Released histamine was also detected in cat skin, and raised levels were found in plasma after intravenous injection of morphine. 

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