parasympathetic mediated cerebral vasodilatation

Cerebral vascular resistance and blood flow were widely considered to be regulated solely by tonic innervation of vasoconstrictor adrenergic nerves. However, pieces of evidence suggesting that parasympathetic nitrergic nerve activation elicits vasodilatation in dog and monkey cerebral arteries were found in 1990. Nitric oxide (NO) as a neurotransmitter liberated from parasympathetic postganglionic neurons decreases cerebral vascular tone and resistance and increases cerebral blood flow, which overcome vasoconstrictor responses to norepinephrine liberated from adrenergic nerves...

Cerebral hypoperfusion due to impaired bioavailability of nitric oxide (NO) synthesized by endothelial nitric oxide synthase and neuronal nitric oxide synthase leads to cognitive decline and neurodegeneration in Alzheimer's disease (AD). Risk factors for endothelial dysfunction, such as inadequate lifestyle, cardiovascular/metabolic diseases, and aging, evokes cerebral hypoperfusion, impaired autoregulation, and increased production of amyloid-β peptides (Aβ) in association with vasculogenic memory loss and dementia...

Parasympathetic nerves from the pterygopalatine ganglia provide nitroxidergic innervation to forebrain cerebral blood vessels. Disruption of that innervation attenuates cerebral vasodilatation seen during acute hypertension as does systemic administration of a non-selective nitric oxide synthase (NOS) inhibitor. Although such studies suggest that nitric oxide (NO) released from parasympathetic nerves participates in vasodilatation of cerebral vessels during hypertension, that hypothesis has not been tested with selective local inhibition of neuronal NOS (nNOS)...

This study tested the hypothesis that cerebral vasodilatation during marked acute hypertension is mediated in part through the influence of parasympathetic nerves from the pterygopalatine ganglia. Blood pressure was increased slowly in anesthetized rats after bilateral transection of the parasympathetic nerves. Cerebral blood flow was measured by laser flowmetry. Acutely hypertensive denervated animals developed significantly less cerebral vasodilatation than did control animals with intact nerves. Thus, parasympathetic vasodilator nerves contribute to vasodilatation seen with acute hypertension...

Cerebral cortical perfusion was monitored continuously with laser Doppler flowmetry and quantitative measurements of cerebral blood flow performed with the freely diffusible tracer 4-iodo[N-methyl-14C]antipyrine in the alpha-chloralose-anesthetized cat. The facial nerve was isolated from the brain stem via a posterior fossa craniotomy and electrically stimulated at frequencies of 1, 2, 5, 10, and 20 s-1. A stimulus-locked frequency-dependent increase in cerebral perfusion was seen in the parietal cortex; the mean maximum increase was 91 +/- 22% at 20 s-1...