Small arteries

Acts to constrict small arteries, thereby increasing blood pressure and to contract smooth muscle. Used in cases of peripheral vasomotor collapse. 

Diltiazem inhibits calcium influx via voltage-operated channels and therefore decreases intracellular calcium ion. This decreases smooth muscle tone. Diltiazem dilates both large and small arteries and also inhibits a-adrenoceptor activated calcium influx. It differs from verapamil and nifedipine by its use dependence. In order for the blockade to occur, the channels must be in the activated state. Diltiazem has no significant affinity for calmodulin. The side effects are headache, edema, and dizziness. 

At the other extreme are those acute stroke patients who have no visible arterial occlusion whatsoever, presumably because their infarcts were due to lesions in small arteries that cannot be imaged, or because an embolus in a large proximal artery has broken up spontaneously. Several smdies (again using catheter angiography rather than CTA) have shown that such patients generally enjoy relatively favorable outcomes. 

Ischemic stroke has numerous causes. Cerebral infarction may result from large artery atherosclerosis, cardiac embolism, small artery lipohyalinosis, cryptogenic embolism, or, more rarely, from other diverse conditions such as arterial dissection, infective endocarditis, and sickle cell disease. Arterial occlusion is the cause of at least 80% of acute cerebral infarctions. " ... 

N.H. Buus, U. Simonsen, H.K. Pilegaard, and N.J. Mulvaney, Nitric oxide, prostanoid and non-NO, non-prostanoid involvement in acetylcholine relaxation of isolated human small arteries. Br. J. Pharmacol. 129, 184-192 (2002). 

Wier We don t find an effect of APB on high K+ contraction if phentolamine is present. With respect to your mechanism of tonic contraction, which you indicated was dependent on Ca2+ influx, in the mesenteric small artery that we study, which develops a tonic contraction, this isn t accompanied by tonic elevation of Ca2+, but rather by these asynchronous Ca2+ waves that we have already seen. Nevertheless, when we add up all these Ca2+ indicator signals we get something that looks like a steady elevated level of Ca2+. We would say that in that tissue the dependence on Ca2+ influx is to keep the SR going, to keep generating these waves. Is this relevant to your tissue ... 

How are SR Ca2+ stores organized in small arteries with myogenic tone ... 

An interesting idea is that in small arteries such as the rat basilar STOCs elicited by sparks can exert a negative feedback on the membrane potential of the smooth muscle syncytium (cells are linked by low resistance pathways) the hyperpolarization so produced will reduce Ca2+ entry through voltage-dependent Ca2+ channels. Thus, in pressurized arteries where the membrane potential is lower than in the relaxed state and there is significant Ca2+ influx into... 

In an earlier chapter we called attention to the large inborn anatomical differences in the size and pattern of blood vessels which carry blood from the heart to the brain. This could be an important predisposing factor in senile dementia since a mild arteriosclerosis involving small arteries could be more than the equivalent of a severe arteriosclerosis when the arteries are relatively large. 

When applied locally the small arteries close to the surface constrict and thereby reduce the bleeding of open wounds and the swelling of the mucosa, for example in the mouth or nose. The same a-adrenoceptor mediated effect can be used system-ically in patients with a circulatory shock which is caused by a vasodilatation. 

Walker AB, Naderali EK, Chattington PD, Buckingham RE, Williams G. Differential vasoactive effects of the insulin sensitizers rosiglitazone (BRL 49653) and troglitazone on human small arteries in vitro. Diabetes 1998 47 810-4. 

Rizzoni, D., Ported, E., Piccoli, A., et al. 1998. Effects of losartan and enalapril on small artery structure in hypertensive rats. Hypertension 32 305-310. 

Eskildsen-Helmond YE, Mulvany MJ. 2003. Pressure-induced activation of extracellular signal-regulated kinase 1/2 in small arteries. Hypertension 41 891-897. 

H. Gustafsson and H. Hilsson, Rhythmic Contractions of Isolated Small Arteries from Rat Role of Calcium, Acta Physiol. Scand. 149, 283-291 (1993). 

Amarenco P, Hauw JJ (1990) Cerebellar infarction in the territory of the anterior and inferior cerebellar artery. A clinico-pathological study of 20 cases. Brain 113 139-155 Baquis GD, Pessin MS, Scott RM (1985) Limb shaking - a carotid TIA. Stroke 16 444-448 Barth A, Bogousslavsky J, Regli F (1994) Infarcts in the territory of the lateral branch of the posterior inferior cerebellar artery. J Neurol Neurosurg Psychiatry 57 1073-1076 Baumgartner RW, Sidler C, Mosso M et al (2003) Ischemic lacunar stroke in patients with and without potential mechanism other than small-artery disease. Stroke 34 653-659... 

Hypertension is regarded as the main clinically observable risk factor to cause microbleeds (Roob et al. 1999). Recent findings suggest that microbleeds on T2 -weighted MRI are an indicator of advanced small artery disease of the brain with an increased... 

G proteins are another family of membrane proteins believed to modulate mechanochemical transduction pathways. Mechanical stimulation changes the conformation of G protein that leads to growth-factorlike changes that initiate secondary messenger cascades leading to cell growth. It has been reported that cyclic strain of smooth muscle cells significantly decreased steady-state levels of G protein and adenylate cyclase activity. Muscular stimulation also appears to be coupled with G protein activation in small arteries. 

Nisoldipine (Fig. 7.7) is an analogue of nifedipine, but it is at least five to ten times more potent than nifedipine on arterial smooth muscle, without affecting myocardial contractility. It also possesses a very potent and selective relaxation activity on small arteries, and therefore it can be used for the treatment of hypertension. Since its duration is limited by a massive hepatic first-pass effect, it is currently used as an extended-release formulation for once-daily administration. 

The mechanical force most relevant to platelet-mediated thrombosis is shear stress. The normal time-averaged levels of venous and arterial shear stresses range between 1-5 dyn/cm2 and 6 10 dyn/cm2, respectively. However, fluid shear stress may reach levels well over 200 dyn/cm2 in small arteries and arterioles partially obstructed by atherosclerosis or vascular spasm. The cone-and-plate viscometer and parallel-plate flow chamber are two of the most common devices used to simulate fluid mechanical shearing stress conditions in blood vessels. 

The test is conducted by using the mechanically congested A. centralis of the rabbit ear. The injection is directed into the distal direction. A 7,5 % solution of thiopental can serve as a positive control because it induces severe inflammatory reactions. The further procedure includes evaluation scores being used as for the i.v. injections. To eliminate the species-specific influence of small rodents (small artery) it is also recommended to use non-rodents like the dog. 

Angiotensin receptor Angiotensin II Increase blood pressure (by constricting small arteries)... 

The meninges are supplied by branches of the external carotid artery, internal carotid artery and vertebral arteries. The most prominent branches from the external carotid artery are the middle meningeal artery and tributaries of the ascending pharyngeal and occipital arteries. Most of the branches from the internal carotid artery arise near the cavernous sinus and from the ophthalmic artery in the orbit. Branches from the vertebral artery arise at the foramen magnum. There are numerous meningeal anastomoses between these small arteries. 

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