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sensory end organ that responds to changes in osmotic pressure

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/03 01:28:58」(JST)

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An osmoreceptor is a sensory receptor primarily found in the hypothalamus of most homeothermic organisms that detects changes in osmotic pressure. Osmoreceptors can be found in several structures, including the organum vasculosum of the lamina terminalis (OVLT) and the subfornical organ (SFO). They contribute to fluid balance in the body.

Mechanism in humans

Osmoreceptors, as the name suggests, sense change in osmotic pressure. When the osmotic pressure of blood changes (i.e. it is more or less dilute), water diffusion into and out of the osmoreceptor cells changes. That is, they expand when the blood plasma is more dilute and contract with higher concentration. This causes an afferent neural signal to be sent to the hypothalamus, which increases or decreases vasopressin (ADH) secretion from the posterior pituitary to return blood concentration to normal.

Macula densa

The macula densa region of the kidney's juxtaglomerular apparatus is another modulator of blood osmolality. The macula densa responds to changes in osmotic pressure through changes in the rate of sodium ion flow through the nephron. Decreased Cl⁻ flow stimulates tubuloglomerular autoregulation, a signal (thought to be regulated by adenosine) sent to the nearby juxtaglomerular cells of the afferent arteriole, causing the JG cells to release the protease renin into circulation. Renin cleaves the zymogen angiotensinogen, always present in plasma as a result of constitutive production in the liver, into a second inactive form, angiotensin I, which is then converted to its active form, angiotensin II, by angiotensin converting enzyme (ACE), which is widely distributed in the small vessels of the body, but particularly concentrated in the pulmonary capillaries of the lungs. Angiotensin II exerts systemwide effects, triggering aldosterone release from the adrenal cortex, direct vasoconstriction, and thirst behaviors originating in the hypothalamus.

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1. 抗利尿ホルモン不適合分泌（SIADH）症候群の病態生理および病因 pathophysiology and etiology of the syndrome of inappropriate antidiuretic hormone secretion siadh
2. Etiology and evaluation of hypernatremia in adults
3. 尿崩症における尿量 urine output in diabetes insipidus
4. 低ナトリウム血症の治療：抗利尿ホルモン不適合分泌（SIADH）症候群およびreset osmostat症候群 treatment of hyponatremia syndrome of inappropriate antidiuretic hormone secretion siadh and reset osmostat

English Journal

Full-length transient receptor potential vanilloid 1 channels mediate calcium signals and possibly contribute to osmoreception in vasopressin neurones in the rat supraoptic nucleus.

Moriya T1, Shibasaki R2, Kayano T3, Takebuchi N2, Ichimura M2, Kitamura N1, Asano A4, Hosaka YZ5, Forostyak O6, Verkhratsky A7, Dayanithi G8, Shibuya I9.
Cell calcium.Cell Calcium.2014 Nov 15. pii: S0143-4160(14)00185-7. doi: 10.1016/j.ceca.2014.11.003. [Epub ahead of print]
Neurones in the supraoptic nucleus (SON) of the hypothalamus possess intrinsic osmosensing mechanisms, which are lost in transient receptor potential vanilloid 1 (Trpv1)-knock-out mice. The molecular nature of the osmosensory mechanism in SON neurones is believed to be associated with the N-terminal
PMID 25479918

Cell-specific retrograde signals mediate antiparallel effects of angiotensin II on osmoreceptor afferents to vasopressin and oxytocin neurons.

Stachniak TJ1, Trudel E2, Bourque CW3.
Cell reports.Cell Rep.2014 Jul 24;8(2):355-62. doi: 10.1016/j.celrep.2014.06.029. Epub 2014 Jul 17.
Homeostatic control of extracellular fluid osmolality in rats requires a parallel excitation of vasopressin (VP) and oxytocin (OT) neurosecretory neurons by osmoreceptor afferents to regulate the amount of water and sodium in the urine under normal conditions. However, during decreased blood volume
PMID 25043186

Osmoreceptors do not exhibit a sex-dependent modulation of forearm skin blood flow and sweating.

Barrera-Ramirez J, McGinn R, Carter MR, Franco-Lopez H, Kenny GP.
Physiological reports.Physiol Rep.2014 Feb 7;2(2):e00226. doi: 10.1002/phy2.226. eCollection 2014.
Studies show that increases in plasma osmolality result in a delayed onset threshold of thermoeffector responses. However, it remains unclear if there are sex-related differences in the osmotically induced changes in both sweating and cutaneous vascular conductance (CVC). Nine young men and nine you
PMID 24744895