Cerebrovascular reactivity changes after sublingual glycine intake

Mashkovtseva E.V.1, Rudnikova N.A.2, Kopylova V.S., Nartsissov Y.R.3

Institute of Cytochemistry and Molecular Pharmacology, 6th Radial’naya str., 24/14. Moscow, Russia. E-mail:

1Pirogov Russian National Research Medical University, Ostrovityanova str., 1/7. Moscow, Russia. E-mail:

2Postgraduate Education Academy of FGBU FNKC FMBA, Volokolamskoye av., 91. Moscow, Russia

3Biomedical Research Group, BiDiPharma GmbH, 22962, Siek, Germany. E-mail:

Cerebrovascular reactivity is an important indicator of human adaptation – vessel diameter should change due to varied environment to optimize brain supplying with oxygen and nutrients. The low reactivity degree correlates with the severity of cardiovascular diseases and the consequences of acute brain ischemia, meanwhile its measurement in healthy people indirectly relies on the central nervous system adaptivness.

Glycine taken sublingually is well-known to effect on autonomic nervous system, vascular tonus and cognitive functioning. Glycine is one of the common essential aminoacids and also a neurotransmitter having a high affinity to glycine inhibitory and NMDA excitory receptors. Direct glycine application on brain arterioles leading to their dilation was experimentally shown. So glycine is to be a part of cardiovascular reactivity system but its direct impact is still underexplored.

Transcranial Doppler of middle cerebral arteries (MCA) of 30 healthy volunteers was performed using US scanner Mindray DC-80. Linear systolic and diastolic blood flow velocity, resistance index and pulsation index were evaluated. Cerebrovascular reactivity was discovered along with 1 g glycine/placebo sublingual intake and after hypercapnia functional test (voluntary breath holding) before and after the application.

Left and right MCA linear blood flow velocities increased significantly after 30 days of glycine intake in the study group (p<0,005) and did not change in the control group. The median velocity increase in hypercapnia functional test was 33.73 [23.43; 49.89] cm/s, and the increment was larger after 1g glycine intake than in control group (p=0.09 at the left and p=0.005 at the right). These results confirm glycine impact on cerebrovascular reactivity.


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