| pubmed-article:9883496 | pubmed:abstractText | The control of cardiovascular system is provided not only by regulatory influence of classical neurotransmitters, acetylcholine and noradrenaline, but also some regulatory peptides have very important physiological significance. One of them is somatostatin, a peptide which possess pronounced cardiotropic activity. Somatostatin-like immunoreactivity was found in the heart of several mammals including man; it was detected in the atrial and ventricular myocardium, conductive system of the heart and cardiac postganglionic parasympathetic neurons. Somatostatin co-exists with acetylcholine in presynaptic vagal endings and may be released by high-frequency stimulation of the vagus nerve. The main cardiac effects of somatostatin are heart rate deceleration, decrease of myocardial contractility and slowing of propagation velocity along conductive system of the heart. Somatostatin plays role in cardiac rhythmogenesis. It modifies electrophysiological properties of cardiac pacemaker, modulates cardiac chronotropic action of autonomic nervous system and prevents supraventricular tachyarrhythmias. Somatostatin diminish cardiac output and affects blood pressure level; the character of vascular effects evoked by this peptide may be different in various species of animals. Somatostatin increases peripheral vascular resistance and provokes a decrease of regional blood flow, especially in mesenterial and hepatoportal vessels. This effect is great of clinical importance in case of gastroduodenal and oesophageal bleedings. Cardiovascular effects of somatostatin may result from its modulatory action on presynaptic release of acetylcholine, noradrenaline and other humoral substances. On the other hand, some effects of somatostatin result from its transmitter action which is provided by interaction of somatostatin with own receptors. Somatostatin receptors are coupled with adenylate cyclase activity and ion channels through inhibitory G-proteins. Excitation of somatostatin receptors causes a decrease of intracellular cAMP content, inhibition of inward calcium current and activation of potassium membrane conductance. There exist five different subtypes of somatostatin receptors which have different structure, pharmacological properties and distribution in various tissues. The data presented in this review make it possible to conclude that cardiovascular effects of somatostatin are very important part in the spectrum of physiological activity of this peptide. | lld:pubmed |
