Editing Vasoconstriction (section)

===Endogenous===
Vasoconstriction is a procedure of the body that averts [[orthostatic hypotension]]. It is part of a body [[negative feedback]] loop in which the body tries to restore homeostasis (maintain constant internal environment).{{citation needed|date=June 2021}}

For example, vasoconstriction is a hypothermic preventative in which the blood vessels constrict and blood must move at a higher pressure to actively prevent a hypoxic reaction. [[Adenosine triphosphate|ATP]] is used as a form of energy to increase this pressure to heat the body. Once homeostasis is restored, the blood pressure and ATP production regulates. Vasoconstriction also occurs in superficial blood vessels of [[warm-blooded]] animals when their ambient environment is cold; this process diverts the flow of heated blood to the center of the animal, preventing the loss of heat.{{Citation needed|date=June 2021}}

{| class="wikitable"
|-
!Vasoconstrictor<ref name=boron/>
!Receptor <br> (↑ = opens. ↓ = closes)<ref name=boron/> <br> <span style="font-size:85%;"> On [[vascular smooth muscle cells]] if not otherwise specified</span>
!Transduction <br> (↑ = increases. ↓ = decreases)<ref name=boron>Unless else specified in box, then ref is: {{cite book |author=Walter F. Boron |title=Medical Physiology: A Cellular And Molecular Approaoch |publisher=Elsevier/Saunders |year= 2005|isbn=1-4160-2328-3 }} Page 479</ref>
|-
| Stretch || ↑[[Stretch-activated ion channel]]s
|rowspan=2| [[depolarization]] -->
* open [[Voltage-dependent calcium channel|VDCC]]s (primarily) --> ↑intracellular Ca<sup>2+</sup>
* ↑Voltage-gated [[sodium channel|Na<sup>+</sup> channel]]s -->
** more depolarization --> open [[Voltage-dependent calcium channel|VDCC]]s --> ↑intracellular Ca<sup>2+</sup>
** ↓[[Sodium-calcium exchanger|Na<sup>+</sup>-Ca<sup>2+</sup> exchanger]] activity --> ↑intracellular Ca<sup>2+</sup>
|-
| [[adenosine triphosphate|ATP]] (intracellular) || ↓[[ATP-sensitive potassium channel|ATP-sensitive K<sup>+</sup> channel]]
|-
| [[adenosine triphosphate|ATP]] (extracellular) || ↑[[P2X receptor]] || ↑Ca<sup>2+</sup>
|-
|[[Neuropeptide Y|NPY]] || [[NPY receptor]]
|| Activation of [[gi alpha subunit|G<sub>i</sub>]] --> ↓[[cyclic adenosine monophosphate|cAMP]] --> ↓[[protein kinase A|PKA]] activity --> ↓[[phosphorylation]] of [[myosin light chain kinase|MLCK]] --> ↑MLCK activity --> ↑phosphorylation of [[myosin light chain|MLC]] (calcium-independent)
|-
| [[adrenergic agonists]] <br> e.g., [[epinephrine]], [[norepinephrine]], and [[dopamine]]|| ↑[[alpha-1 adrenergic receptor|α<sub>1</sub> adrenergic receptor]]
|rowspan=3| Activation of [[gq alpha subunit|G<sub>q</sub>]] --> ↑[[phospholipase C|PLC]] activity --> ↑[[Inositol triphosphate|IP<sub>3</sub>]] and [[diacylglycerol|DAG]] --> activation of [[Inositol triphosphate receptor|IP<sub>3</sub> receptor]] in [[sarcoplasmic reticulum|SR]] --> ↑intracellular Ca<sup>2+</sup>
|-
| [[thromboxane]] || ↑[[thromboxane receptor]]
|-
| [[endothelin]] || ↑[[endothelin receptor]] ET<sub>A</sub>
|-
|rowspan=2| [[angiotensin II]] || ↑[[Angiotensin receptor#AT1|Angiotensin receptor 1]]
|
* On smooth muscle cells: Activation of [[gq alpha subunit|G<sub>q</sub>]] --> ↑[[phospholipase C|PLC]] activity --> ↑[[Inositol triphosphate|IP<sub>3</sub>]] and [[diacylglycerol|DAG]] --> activation of [[Inositol triphosphate receptor|IP<sub>3</sub> receptor]] in [[sarcoplasmic reticulum|SR]] --> ↑intracellular Ca<sup>2+</sup>
* On [[endothelium]]: [[endothelin]] synthesis<ref name=lange6th/>
|-
|  || open [[Voltage-dependent calcium channel|VDCC]]s --> ↑intracellular Ca<sup>2+</sup><ref name=boron2>{{cite book |author=Walter F. Boron |title=Medical Physiology: A Cellular And Molecular Approach |publisher=Elsevier/Saunders |year= 2005|isbn=1-4160-2328-3 }} Page 771</ref>
|-
| [[Asymmetric dimethylarginine]] ||||Reduced production of [[nitric oxide]]
|-
|rowspan=2| [[Vasopressin|Antidiuretic hormone (ADH or Vasopressin)]] || [[Arginine vasopressin receptor 1]] (V1) on smooth muscle cells
| Activation of [[gq alpha subunit|G<sub>q</sub>]] --> ↑[[phospholipase C|PLC]] activity --> ↑[[Inositol triphosphate|IP<sub>3</sub>]] and [[diacylglycerol|DAG]] --> activation of [[Inositol triphosphate receptor|IP<sub>3</sub> receptor]] in [[sarcoplasmic reticulum|SR]] --> ↑intracellular Ca<sup>2+</sup>
|-
| [[Arginine vasopressin receptor]] on endothelium || [[Endothelin]] production<ref name=lange6th/>
|-
|
* Products of [[platelet activation]]<ref name=lange6th>{{cite book |author1=Rod Flower |author2=Humphrey P. Rang |author3=Maureen M. Dale |author4=Ritter, James M. |title=Rang & Dale's pharmacology |publisher=Churchill Livingstone |location=Edinburgh |year=2007 |isbn=978-0-443-06911-6 }}</ref>
* [[Endotoxin]]<ref name=lange6th/>
* [[Thrombin]]<ref name=lange6th/>
* [[insulin]]<ref name=lange6th/>
* [[Hypoxia (medical)|Hypoxia]]<ref name=lange6th/>
* Low [[shear stress]]<ref name=lange6th/>
| Various receptors on [[endothelium]]<ref name=lange6th/>  || [[Endothelin]] production<ref name=lange6th/>
|}