Limits...
Amino acids that centrally influence blood pressure and regional blood flow in conscious rats.

Takemoto Y - J Amino Acids (2012)

Bottom Line: This paper firstly describes why amino acids are selected and outlines how the brain regulates blood pressure and regional blood flow.Thereafter, cardiovascular actions of some of amino acids at the mechanism level will be discussed based upon findings of pharmacological and regional blood flow measurements.Several examined amino acids in addition to the established neurotransmitter amino acids appear to differentially activate brain structures to produce changes in blood pressure and regional blood flows.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Graduate School Biomedical Sciences, Hiroshima University, Kasumi-cho 1-2-3, Minami-ku, Hiroshima, 734-8551, Japan.

ABSTRACT
Functional roles of amino acids have increasingly become the focus of research. This paper summarizes amino acids that influence cardiovascular system via the brain of conscious rats. This paper firstly describes why amino acids are selected and outlines how the brain regulates blood pressure and regional blood flow. This section includes a concise history of amino acid neurotransmitters in cardiovascular research and summarizes brain areas where chemical stimulations produce blood pressure changes mainly in anesthetized animals. This is followed by comments about findings regarding several newly examined amino acids with intracisternal stimulation in conscious rats that produce changes in blood pressure. The same pressor or depressor response to central amino acid stimulations can be produced by distinct mechanisms at central and peripheral levels, which will be briefly explained. Thereafter, cardiovascular actions of some of amino acids at the mechanism level will be discussed based upon findings of pharmacological and regional blood flow measurements. Several examined amino acids in addition to the established neurotransmitter amino acids appear to differentially activate brain structures to produce changes in blood pressure and regional blood flows. They may have physiological roles in the healthy brain, but pathological roles in the brain with cerebral vascular diseases such as stroke where the blood-brain barrier is broken.

No MeSH data available.


Related in: MedlinePlus

Higher head pressure produces greater flow when the tube keeps the same diameter without any influence.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3368589&req=5

fig7: Higher head pressure produces greater flow when the tube keeps the same diameter without any influence.

Mentions: Before seeing the hemodynamic data, explanation of flow measurement and relationship among regional blood flow, regional blood flow resistance, and blood pressure would be needed. An electromagnetic flow probe set around the artery monitors the flow volume rate (not velocity) in the freely moving rat [137] (Figure 6). The blood flow rate (volume/min/100 g weight) measured in an artery just before the vascular bed of an organ reflects the net changes in sizes of arterioles within the organ. Namely, stronger arteriolar dilatation produces more arterial blood flow, but stronger vasoconstriction produces less flow. At rest, the size of arteriole is mainly determined by the basal tone of vascular sympathetic neurons (Figure 3). When the vascular sympathetic discharge is increased, the resultant vasoconstriction reduces flow to the corresponding artery. When arterioles in a particular vascular bed are not under the control of sympathetic neurons, higher blood pressure produces blood flow increase. Namely, when tube (artery) size is constant and head (blood) pressure is different, higher head pressure produces greater flow (Figure 7). Therefore, to take the influence of blood pressure changes into account, blood flow resistance or conductance is used to evaluate the net effect of the vascular bed. The studies have expressed blood flow resistance or vascular resistance that is blood pressure divided by flow. Changes in blood pressure always influence blood flow, but changes in blood flow can make changes in blood pressure when they influence the total peripheral flow resistance that is the net change in all the vascular beds. When liquid in a tank flows out from the exits, constricted tubes together produce high back pressure, but dilated tubes together produce low back pressure, and a combination of constricted and dilated tubes results in no change in back pressure (Figure 8). The final example shows what happened when the rat walked spontaneously. The flow was shifted from carotid artery to hindquarters (aortic terminal for legs) without changes in blood pressure that was also supported with an increase in cardiac output [2]. However, grooming behavior increased blood pressure slightly (by 10 mmHg) with blood shift in the opposite direction [1]. Here, we see changes in regional blood flow resistance when amino acids produce the pressor response.


Amino acids that centrally influence blood pressure and regional blood flow in conscious rats.

Takemoto Y - J Amino Acids (2012)

Higher head pressure produces greater flow when the tube keeps the same diameter without any influence.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3368589&req=5

fig7: Higher head pressure produces greater flow when the tube keeps the same diameter without any influence.
Mentions: Before seeing the hemodynamic data, explanation of flow measurement and relationship among regional blood flow, regional blood flow resistance, and blood pressure would be needed. An electromagnetic flow probe set around the artery monitors the flow volume rate (not velocity) in the freely moving rat [137] (Figure 6). The blood flow rate (volume/min/100 g weight) measured in an artery just before the vascular bed of an organ reflects the net changes in sizes of arterioles within the organ. Namely, stronger arteriolar dilatation produces more arterial blood flow, but stronger vasoconstriction produces less flow. At rest, the size of arteriole is mainly determined by the basal tone of vascular sympathetic neurons (Figure 3). When the vascular sympathetic discharge is increased, the resultant vasoconstriction reduces flow to the corresponding artery. When arterioles in a particular vascular bed are not under the control of sympathetic neurons, higher blood pressure produces blood flow increase. Namely, when tube (artery) size is constant and head (blood) pressure is different, higher head pressure produces greater flow (Figure 7). Therefore, to take the influence of blood pressure changes into account, blood flow resistance or conductance is used to evaluate the net effect of the vascular bed. The studies have expressed blood flow resistance or vascular resistance that is blood pressure divided by flow. Changes in blood pressure always influence blood flow, but changes in blood flow can make changes in blood pressure when they influence the total peripheral flow resistance that is the net change in all the vascular beds. When liquid in a tank flows out from the exits, constricted tubes together produce high back pressure, but dilated tubes together produce low back pressure, and a combination of constricted and dilated tubes results in no change in back pressure (Figure 8). The final example shows what happened when the rat walked spontaneously. The flow was shifted from carotid artery to hindquarters (aortic terminal for legs) without changes in blood pressure that was also supported with an increase in cardiac output [2]. However, grooming behavior increased blood pressure slightly (by 10 mmHg) with blood shift in the opposite direction [1]. Here, we see changes in regional blood flow resistance when amino acids produce the pressor response.

Bottom Line: This paper firstly describes why amino acids are selected and outlines how the brain regulates blood pressure and regional blood flow.Thereafter, cardiovascular actions of some of amino acids at the mechanism level will be discussed based upon findings of pharmacological and regional blood flow measurements.Several examined amino acids in addition to the established neurotransmitter amino acids appear to differentially activate brain structures to produce changes in blood pressure and regional blood flows.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Graduate School Biomedical Sciences, Hiroshima University, Kasumi-cho 1-2-3, Minami-ku, Hiroshima, 734-8551, Japan.

ABSTRACT
Functional roles of amino acids have increasingly become the focus of research. This paper summarizes amino acids that influence cardiovascular system via the brain of conscious rats. This paper firstly describes why amino acids are selected and outlines how the brain regulates blood pressure and regional blood flow. This section includes a concise history of amino acid neurotransmitters in cardiovascular research and summarizes brain areas where chemical stimulations produce blood pressure changes mainly in anesthetized animals. This is followed by comments about findings regarding several newly examined amino acids with intracisternal stimulation in conscious rats that produce changes in blood pressure. The same pressor or depressor response to central amino acid stimulations can be produced by distinct mechanisms at central and peripheral levels, which will be briefly explained. Thereafter, cardiovascular actions of some of amino acids at the mechanism level will be discussed based upon findings of pharmacological and regional blood flow measurements. Several examined amino acids in addition to the established neurotransmitter amino acids appear to differentially activate brain structures to produce changes in blood pressure and regional blood flows. They may have physiological roles in the healthy brain, but pathological roles in the brain with cerebral vascular diseases such as stroke where the blood-brain barrier is broken.

No MeSH data available.


Related in: MedlinePlus