alpha-1 (α₁) adrenergic receptors are

G protein-coupled receptors G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

(GPCRs) associated with the G_q

heterotrimeric G protein Heterotrimeric G protein, also sometimes referred to as the ''"large" G proteins'' (as opposed to the subclass of smaller, monomeric small GTPases) are membrane-associated G proteins that form a heterotrimeric complex. The biggest non-structu ...

. α₁-adrenergic receptors are subdivided into three highly homologous subtypes, i.e., α_1A-, α_1B-, and α_1D-adrenergic receptor subtypes. There is no α_1C receptor. At one time, there was a subtype known as α_1C, but it was found to be identical to the previously discovered α_1A receptor subtype. To avoid confusion, naming was continued with the letter D.

Catecholamine A catecholamine (; abbreviated CA) is a monoamine neurotransmitter, an organic compound that has a catechol (benzene with two hydroxyl side groups next to each other) and a side-chain amine. Catechol can be either a free molecule or a subst ...

s like

norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...

(noradrenaline) and

epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...

(adrenaline) signal through the α₁-adrenergic receptors in the

central Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

and

peripheral nervous system The peripheral nervous system (PNS) is one of two components that make up the nervous system of bilateral animals, with the other part being the central nervous system (CNS). The PNS consists of nerves and ganglia, which lie outside the brain ...

s. The crystal structure of the α_1B-adrenergic receptor subtype has been determined in complex with the inverse agonist (+)-cyclazosin.

Effects

The α₁-adrenergic receptor has several general functions in common with the α₂-adrenergic receptor, but also has specific effects of its own. α₁-receptors primarily mediate

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

contraction, but have important functions elsewhere as well. The

neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neuro ...

norepinephrine has higher affinity for the α₁ receptor than does the hormone

adrenaline Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...

Smooth muscle

In smooth muscle cells of

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s the principal effect of activation of these receptors is

vasoconstriction Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vessel ...

. Blood vessels with α₁-adrenergic receptors are present in the

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, the

sphincters A sphincter is a circular muscle that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning. Sphincters are found in many animals. There are over 60 types in the hum ...

gastrointestinal system The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans and ...

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...

(

renal artery The renal arteries are paired arteries that supply the kidneys with blood. Each is directed across the crus of the diaphragm, so as to form nearly a right angle. The renal arteries carry a large portion of total blood flow to the kidneys. Up to a ...

) and

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. During the

fight-or-flight response The fight-or-flight or the fight-flight-or-freeze response (also called hyperarousal or the acute stress response) is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival. It was first des ...

vasoconstriction results in decreased blood flow to these organs. This accounts for the pale appearance of the skin of an individual when frightened. It also induces contraction of the internal urethral sphincter of the

urinary bladder The urinary bladder, or simply bladder, is a hollow organ in humans and other vertebrates that stores urine from the kidneys before disposal by urination. In humans the bladder is a distensible organ that sits on the pelvic floor. Urine enters ...

, although this effect is minor compared to the relaxing effect of β₂-adrenergic receptors. In other words, the overall effect of sympathetic stimuli on the bladder is relaxation, in order to inhibit

micturition Urination, also known as micturition, is the release of urine from the urinary bladder through the urethra to the outside of the body. It is the urinary system's form of excretion. It is also known medically as micturition, voiding, uresis, ...

upon anticipation of a stressful event. Other effects on smooth muscle are contraction in: *

Ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional epit ...

Uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...

(when pregnant): this is minor compared to the relaxing effects of the β₂ receptor, agonists of which - notably albuterol/salbutamol - were formerly used to inhibit premature labor. *

Urethral sphincter The urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. The two muscles are either the male or female external urethral sphincter and the internal urethral sphincter. When either of th ...

* Bronchioles (although minor to the relaxing effect of β₂ receptor on bronchioles) *

Iris dilator muscle The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. The pupillary dilator consists of a spokelike ...

Page 163 * Seminal tract, resulting in

ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential componen ...

Neuronal

Activation of α₁-adrenergic receptors produces

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

and partially mediates the efficacy of appetite suppressants like

phenylpropanolamine Phenylpropanolamine (PPA) is a sympathomimetic agent which is used as a decongestant and appetite suppressant. It was commonly used in prescription and over-the-counter cough and cold preparations. In veterinary medicine, it is used to contr ...

and

amphetamine Amphetamine (contracted from alpha- methylphenethylamine) is a strong central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity. It is also commonly used ...

in the treatment of

obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...

. Norepinephrine has been shown to decrease cellular excitability in all layers of the

temporal cortex The temporal lobe is one of the four major lobes of the cerebral cortex in the brain of mammals. The temporal lobe is located beneath the lateral fissure on both cerebral hemispheres of the mammalian brain. The temporal lobe is involved in pro ...

, including the

primary auditory cortex The auditory cortex is the part of the temporal lobe that processes auditory information in humans and many other vertebrates. It is a part of the auditory system, performing basic and higher functions in hearing, such as possible relations to ...

. In particular, norepinephrine decreases

glutamatergic Glutamatergic means "related to glutamate". A glutamatergic agent (or drug) is a chemical that directly modulates the excitatory amino acid (glutamate/aspartate) system in the body or brain. Examples include excitatory amino acid receptor agonis ...

excitatory

postsynaptic potential Postsynaptic potentials are changes in the membrane potential of the postsynaptic terminal of a chemical synapse. Postsynaptic potentials are graded potentials, and should not be confused with action potentials although their function is to ini ...

s by the activation of α₁-adrenergic receptors. Norepinephrine also stimulates

serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...

release by binding α1-adrenergic receptors located on serotonergic neurons in the raphe. α1-adrenergic receptor subtypes increase inhibition in the olfactory system, suggesting a synaptic mechanism for noradrenergic modulation of olfactory driven behaviors.

Other

* Both positive and negative

inotropic An inotrope is an agent that alters the force or energy of muscular contractions. Negatively inotropic agents weaken the force of muscular contractions. Positively inotropic agents increase the strength of muscular contraction. The term ''inotro ...

effects on

heart muscle Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle tha ...

* Secretion from

salivary gland The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands. Salivary gla ...

* Increase salivary

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

levels * Glycogenolysis and

gluconeogenesis Gluconeogenesis (GNG) is a metabolic pathway that results in the generation of glucose from certain non-carbohydrate carbon substrates. It is a ubiquitous process, present in plants, animals, fungi, bacteria, and other microorganisms. In vertebrat ...

liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...

. * Secretion from sweat glands * Contraction of the urinary bladder urothelium and lamina propria * Na⁺ reabsorption from

** Stimulate

proximal tubule The proximal tubule is the segment of the nephron in kidneys which begins from the renal pole of the Bowman's capsule to the beginning of loop of Henle. It can be further classified into the proximal convoluted tubule (PCT) and the proximal strai ...

NHE3 Page 787 ** Stimulate

basolateral Na-K ATPase * Activate

mitogenic A mitogen is a small bioactive protein or peptide that induces a cell to begin cell division, or enhances the rate of division (mitosis). Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen. The mechanism of action of a ...

responses and regulate growth and proliferation of many cells * Involved in the detection of mechanical feedback on the

hypoglossal The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated by ...

motor neurons which allow a long-term facilitation in respiration in response to repeated

apnea Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there ...

Signaling cascade

α₁-Adrenergic receptors are members of the

G protein-coupled receptor G protein-coupled receptors (GPCRs), also known as seven-(pass)-transmembrane domain receptors, 7TM receptors, heptahelical receptors, serpentine receptors, and G protein-linked receptors (GPLR), form a large group of evolutionarily-related p ...

superfamily. Upon activation, a

, G_q, activates

phospholipase C Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role ...

(PLC), which causes

phosphatidylinositol Phosphatidylinositol (or Inositol Phospholipid) consists of a family of lipids as illustrated on the right, where red is x, blue is y, and black is z, in the context of independent variation, a class of the phosphatidylglycerides. In such molecul ...

to be transformed into inositol trisphosphate (IP₃) and diacylglycerol (DAG). While DAG stays near the membrane, IP₃ diffuses into the cytosol and to find the IP₃ receptor on the endoplasmic reticulum, triggering calcium release from the stores. This triggers further effects, primarily through the activation of an enzyme Protein Kinase C. This enzyme, as a kinase, functions by phosphorylation of other enzymes causing their activation, or by phosphorylation of certain channels leading to the increase or decrease of electrolyte transfer in or out of the cell.

Activity during exercise

During exercise, α₁-adrenergic receptors in active muscles are attenuated in an exercise intensity-dependent manner, allowing the β₂-adrenergic receptors which mediate vasodilation to dominate. In contrast to α₂-adrenergic receptors, α₁-adrenergic-receptors in the arterial vasculature of skeletal muscle are more resistant to inhibition, and attenuation of α1-adrenergic-receptor-mediated vasoconstriction only occurs during heavy exercise. Note that only active muscle α₁-adrenergic receptors will be blocked. Resting muscle will not have its α₁-adrenergic receptors blocked, and hence the overall effect will be α₁-adrenergic-mediated vasoconstriction.

Ligands

; Agonists *

Cirazoline Cirazoline is a full agonist at the α1A adrenergic receptor, a partial agonist at both the α1B and α1D adrenergic receptors, and a nonselective antagonist to the α2 adrenergic receptor. It is believed that this combination of properties ...

(

vasoconstrictor Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels, in particular the large arteries and small arterioles. The process is the opposite of vasodilation, the widening of blood vess ...

) *

Methoxamine Methoxamine is an α1-adrenergic receptor agonist, somewhat similar in structure to butaxamine and 2,5-DMA. It is no longer marketed. See also * Sertraline * Phenylephrine * Synephrine * Phentolamine Phentolamine, sold under the brand n ...

(

) *

Synephrine Synephrine, or, more specifically, ''p''-synephrine, is an alkaloid, occurring naturally in some plants and animals, and also in approved drugs products as its ''m''-substituted analog known as neo-synephrine. ''p''-Synephrine (or formerly Sympat ...

(mild

) *

Etilefrine Etilefrine is a cardiac stimulant used as an antihypotensive. It is a sympathomimetic amine of the 3-hydroxy-phenylethanolamine series used in treating orthostatic hypotension of neurological, cardiovascular, endocrine or metabolic origin. Intrav ...

(

antihypotensive An antihypotensive agent, also known as a vasopressor agent or simply vasopressor, or pressor, is any substance, whether endogeny (biology), endogenous or a medication, that tends to raise low blood pressure. Some antihypotensive drugs act as vas ...

) *

Metaraminol Metaraminol, previously sold under the brand name Aramine among others and also known as metaradrine, is a stereoisomer of ''meta''-hydroxynorephedrine (3,β-dihydroxyamphetamine), is a potent sympathomimetic amine used in the prevention and tr ...

(

) *

Midodrine Midodrine is a vasopressor/ antihypotensive agent (it raises the blood pressure). Midodrine was approved in the United States by the Food and Drug Administration (FDA) in 1996 for the treatment of dysautonomia and orthostatic hypotension. In A ...

(

) *

Naphazoline Naphazoline is a medicine used as a decongestant, and a vasoconstrictor added to eye drops to relieve red eye. It has a rapid action in reducing swelling when applied to mucous membranes. It is a sympathomimetic agent with marked alpha adrenerg ...

(

decongestant A decongestant, or nasal decongestant, is a type of pharmaceutical drug that is used to relieve nasal congestion in the upper respiratory tract. The active ingredient in most decongestants is either pseudoephedrine or phenylephrine (the latter ...

) *

Norepinephrine Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...

(

) *

Oxymetazoline Oxymetazoline, sold under the brand name Afrin among others, is a topical decongestant and vasoconstrictor medication. It is available over-the-counter as a nasal spray to treat nasal congestion and nosebleeds, as eyedrops to treat eye rednes ...

(

) *

Phenylephrine Phenylephrine is a medication primarily used as a decongestant, to dilate the pupil, to increase blood pressure, and to relieve hemorrhoids. In the United States, it was previously used orally as an over-the-counter decongestant to relieve nas ...

(

) * Pseudoephedrine (

) *

Tetrahydrozoline Tetryzoline (also known as tetrahydrozoline) is a drug used in some over-the-counter eye drops and nasal sprays. Tetryzoline was patented in 1954, and came into medical use in 1959. Side effects Tetryzoline eye drops may cause blurred vision, e ...

(

) *

Xylometazoline Xylometazoline, also spelled xylomethazoline, is a medication used to reduce symptoms of nasal congestion, allergic rhinitis, and sinusitis. Use is not recommended for more than seven days. Use is also not recommended in those less than three m ...

(

)
Sdz-nvi-085
04195-17-7 ; Antagonists *

Acepromazine Acepromazine, acetopromazine, or acetylpromazine (commonly known as ACP, Ace, or by the trade names Atravet or Acezine 2, number depending on mg/ml dose) is a phenothiazine derivative antipsychotic drug. It was used in humans during the 1950s a ...

(antipsychotic, secondary mechanism) * Alfuzosin (used in

benign prostatic hyperplasia Benign prostatic hyperplasia (BPH), also called prostate enlargement, is a noncancerous increase in size of the prostate gland. Symptoms may include frequent urination, trouble starting to urinate, weak stream, inability to urinate, or loss o ...

) * Arotinolol *

Carvedilol Carvedilol, sold under the brand name Coreg among others, is a medication used to treat high blood pressure, congestive heart failure (CHF), and left ventricular dysfunction in people who are otherwise stable. For high blood pressure, it is gen ...

(used in

congestive heart failure Heart failure (HF), also known as congestive heart failure (CHF), is a syndrome, a group of signs and symptoms caused by an impairment of the heart's blood pumping function. Symptoms typically include shortness of breath, excessive fatigue, a ...

; it is a non-selective beta blocker) *

Chlorpromazine Chlorpromazine (CPZ), marketed under the brand names Thorazine and Largactil among others, is an antipsychotic medication. It is primarily used to treat psychotic disorders such as schizophrenia. Other uses include the treatment of bipolar di ...

(antipsychotic and powerful antihypertensive) *

Doxazosin Doxazosin, sold under the brand names Cardura among others, is a medication used to treat symptoms of benign prostatic hyperplasia (enlarged prostate) and hypertension (high blood pressure). For high blood pressure, it is a less preferred option ...

(used in

hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...

and benign prostatic hyperplasia) * Indoramin *

Labetalol Labetalol is a medication used to treat high blood pressure and in long term management of angina. This includes essential hypertension, hypertensive emergencies, and hypertension of pregnancy. In essential hypertension it is generally less pref ...

(used in

; it is a mixed alpha/beta adrenergic antagonist) *

Moxisylyte Moxisylyte, also known as thymoxamine, is a drug used in urology for the treatment of erectile dysfunction. It is an α1-adrenergic antagonist. In the United Kingdom, Moxisylte is marketed as Opilon (Archimedes Pharma UK Ltd) and is used for t ...

Phenoxybenzamine Phenoxybenzamine (marketed under the trade names Dibenzyline and Dibenyline) is a non-selective, irreversible alpha blocker. Uses It is used in the treatment of hypertension, and specifically that caused by pheochromocytoma. It has a slower ons ...

Phentolamine Phentolamine, sold under the brand name Regitine among others, is a reversible nonselective α- adrenergic antagonist. Mechanism Its primary action is vasodilation due to α1 blockade. Non-selective α-blockers can cause a much more pronounced ...

(used in hypertensive emergencies; it is a nonselective alpha-antagonist) *

Prazosin Prazosin is an α1 blocker medication primarily used to treat high blood pressure, symptoms of an enlarged prostate, and nightmares related to post-traumatic stress disorder (PTSD). It is a less preferred treatment of high blood pressure. Oth ...

(used in hypertension) *

Quetiapine Quetiapine, sold under the brand name Seroquel among others, is an atypical antipsychotic medication used for the treatment of schizophrenia, bipolar disorder, and major depressive disorder. Despite being widely used as a sleep aid due to its ...

Risperidone Risperidone, sold under the brand name Risperdal among others, is an atypical antipsychotic used to treat schizophrenia and bipolar disorder. It is taken either by mouth or by injection (subcutaneous or intramuscular). The injectable versions ...

Silodosin Silodosin (known by the trade names Silosoft in India, Urief in Japan, Rapaflo in North America, and Silodyx or Niksol in the European Union) is a medication for the symptomatic treatment of benign prostatic hyperplasia (BPH). It acts as an α1- ...

Tamsulosin Tamsulosin, sold under the brand name Flomax among others, is a medication used to treat symptomatic benign prostatic hyperplasia (BPH) and chronic prostatitis and to help with the passage of kidney stones. The evidence for benefit with a ki ...

(used in benign prostatic hyperplasia) *

Terazosin Terazosin, sold under the brand name Hytrin among others, is a medication used to treat symptoms of an enlarged prostate and high blood pressure. For high blood pressure, it is a less preferred option. It is taken by mouth. Common side effect ...

* Tiamenidine *

Tolazoline Tolazoline is a non-selective competitive α-adrenergic receptor antagonist. It is a vasodilator that is used to treat spasms of peripheral blood vessels (as in acrocyanosis). It has also been used (in conjunction with sodium nitroprusside) ...

Trazodone Trazodone, sold under many brand names, is an antidepressant medication. It is used to treat major depressive disorder, anxiety disorders, and difficulties with sleep. The medication is taken orally. Common side-effects include dry mouth, f ...

* Trimazosin *

Urapidil Urapidil is a sympatholytic antihypertensive drug. It acts as an α1-adrenoceptor antagonist and as an 5-HT1A receptor agonist. Although an initial report suggested that urapidil was also an α2-adrenoceptor agonist, this was not substantiated ...

Various

heterocyclic A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...

antidepressant Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, hea ...

s and

antipsychotic Antipsychotics, also known as neuroleptics, are a class of Psychiatric medication, psychotropic medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought), principally in schizophrenia but ...

s are α₁-adrenergic receptor antagonists as well. This action is generally undesirable in such agents and mediates

side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...

s like

orthostatic hypotension Orthostatic hypotension, also known as postural hypotension, is a medical condition wherein a person's blood pressure drops when standing up or sitting down. Primary orthostatic hypertension is also often referred to as neurogenic orthostatic hyp ...

, and headaches due to excessive vasodilation.

References

External links

* {{Adrenergics Adrenergic receptors