Pharmacology and Physiology of Perivascular Nerves Regulating Vascular Function

Abstract

ABSTRACT-The presence of close apposition between the adrenergic and the non-adrenergic or nitrergic nerve terminals in large cerebral arteries in several species is well documented. The axo-axonal distance between these different types of nerve terminals is substantially closer than the synaptic distance between the adventitial nerve terminals and the outermost layer of smooth muscle in the media. This feature suggests that a functional axo-axonal interaction between nerve terminals is more likely to occur than that between the nerve and muscle. Thus, transmitters released from one nerve terminal may modulate release of transmitters from the neighboring nerve terminals, resulting in a neurogenic response. We have reported that nicotine-induced nitric oxide (NO)-mediated neurogenic vasodilation is dependent on intact sympathetic innervation in porcine and cat cerebral arteries. Evidence also has been presented to indicate that nicotine acts on a 7-nicotinic receptors located on sympathetic nerve terminals, resulting in release of norepinephrine which then diffuses to act on b2-adrenoceptos located on the neighboring nitrergic nerve terminals to release NO and therefore vasodilation. The predominant facilitatory effect of b2-adrenoceptors in releasing NO is compromised by presynaptic a2-adrenoceptors located on the same nerves. Activation of cerebral sympathetic nerves may cause NO-mediated dilation in large cerebral arteries at the base of the brain.

Role of β-adrenergic signaling in masseter muscle

“…β 2 -AR stimulation has been reported to evoke vasodilatation in skeletal muscle, including masseter muscle, and impaired β 2 -AR function is implicated in the maintenance of systemic arterial hypertension [86,87]. β 2 -AR-mediated vasodilatation is caused through the upregulation of endothelial nitric oxide synthase via the PI3-kinase-Akt pathway in mouse pulmonary artery or rat cerebral artery [88,89]. More importantly, cardiorespiratory function and cerebral blood oxygen influence cognitive function, physical performance, and rhythmic movement of the masseter muscle [90–92].…”

Sympathectomy Causes Aggravated Lesions and Dedifferentiation in Large Rabbit Atherosclerotic Arteries without Involving Nitric Oxide

“…Vasodilatation has been observed in response to sympathetic stimulation in several organs, including cerebral vessels [11]. Evidence has been provided implicating the sympathetic nervous system in the functioning of parasympathetic nerves, especially the induction of NOS and release of NO [12, 13].…”