An ultrastructural analysis of the sympathetic innervation of the rabbit ear artery and middle cerebral artery and their branches

Unlike many peripheral vascular beds, the sympathetic nervous system exerts little control on cerebral blood flow. The contractile response of isolated rabbit middle cerebral artery (MCA) segments to electrical field stimulation of its intramural nerves is less than in a similar-sized artery from the ear. This study was undertaken to characterize and compare the perivascular neuromuscular relationships and innervation density of similar-sized arteries varying in diameter from these two different regional arterial beds to see if there were structural correlates for these functional differences.

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Electrical field stimulation-mediated relaxation of rabbit middle cerebral artery. Evidence of a cholinergic endothelium-dependent component.

Circulation Research ◽

10.1161/01.res.70.6.1104 ◽

1992 ◽

Vol 70 (6) ◽

pp. 1104-1112 ◽

Cited By ~ 19

Author(s):

D A Van Riper ◽

J A Bevan

Keyword(s):

Middle Cerebral Artery ◽

Cerebral Artery ◽

Electrical Field Stimulation ◽

Field Stimulation ◽

Electrical Field ◽

Dependent Component

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Neurotransmission in the Sheep Middle Cerebral Artery: Modulation of Responses by 5-HT and Haemolysate

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/jcbfm.1990.71 ◽

1990 ◽

Vol 10 (3) ◽

pp. 409-416 ◽

Cited By ~ 11

Author(s):

Alasdair J. Gaw ◽

Roger M. Wadsworth ◽

Patrick P. A. Humphrey

Keyword(s):

Smooth Muscle ◽

Middle Cerebral Artery ◽

Cerebral Artery ◽

Contractile Response ◽

Electrical Field Stimulation ◽

Field Stimulation ◽

Electrical Field ◽

Noradrenergic Nerves ◽

Uptake Mechanisms ◽

Stimulation Of

In ring sections of the sheep middle cerebral artery, electrical field stimulation elicits a complex response due to the simultaneous release of vasodilator and vasoconstrictor neurotransmitters. Haemolysate abolishes the relaxant effects of the vasodilator neurotransmitter and causes a marked augmentation of the contractile response in both the presence (448 ± 191%) and absence (409 ± 134%) of an intact endothelium. The haemolysate also reverses relaxation induced by sodium nitroprusside or sodium nitrite but has no effect on relaxation induced by 8-Br-cGMP. The vasodilator neurotransmitter therefore appears to act directly on the smooth muscle to cause relaxation by the stimulation of guanylate cyclase. The vasoconstrictor neurotransmitters that are released are antagonised by prazosin (100 n M), ketanserin (100 n M) and atropine (100 n M), which suggests that the transmitters involved are noradrenaline, 5-hydroxytryptamine (5-HT), and acetylcholine, respectively. In the presence of these three antagonists at 10 μ M, there was 86.9 ± 4.8% inhibition. Incubation with 5-HT (10 μ M) causes a marked augmentation of the contractile response (267 ± 56%) to field stimulation that can be reduced by pretreatment with either desipramine or citalopram, inhibitors of noradrenergic and serotoninergic uptake mechanisms, respectively. The 5-HT appears to be taken up into noradrenergic nerves and released as an alternative neurotransmitter upon subsequent stimulation. These actions of haemolysate and 5-HT may be involved in the cerebral vasospasm observed following subarachnoid haemorrhage.

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