biology

Vasoactive intestinal peptide

Vasoactive intestinal peptide is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Vasoactive intestinal peptide rather than just read about it. In short: Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a peptide of 28 amino acid residues that belongs to a glucagon/secretin superfamily, the ligand of class II G protein–coupled receptors.

Key takeaways

Vasoactive intestinal peptide belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Vasoactive intestinal peptide to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Vasoactive intestinal peptide from memory before moving on to harder problems.

Reference excerpt

Vasoactive intestinal peptide, also known as vasoactive intestinal polypeptide or VIP, is a peptide hormone that is vasoactive in the intestine. VIP is a peptide of 28 amino acid residues that belongs to a glucagon/secretin superfamily, the ligand of class II G protein–coupled receptors. VIP is produced in many tissues of vertebrates including the gut, pancreas, neocortex, and suprachiasmatic nuclei of the hypothalamus in the brain. VIP stimulates contractility in the heart, causes vasodilation, increases glycogenolysis, lowers arterial blood pressure and relaxes the smooth muscle of trachea, stomach and gallbladder. In humans, the vasoactive intestinal peptide is encoded by the VIP gene. VIP has a half-life (t½) in the blood of about two minutes.

Function

In the digestive system In the digestive system, VIP seems to induce smooth muscle relaxation (lower esophageal sphincter, stomach, gallbladder), stimulate secretion of water into pancreatic juice and bile, and cause inhibition of gastric acid secretion and absorption from the intestinal lumen. Its role in the intestine is to greatly stimulate secretion of water and electrolytes, as well as relaxation of enteric smooth muscle, dilating peripheral blood vessels, stimulating pancreatic bicarbonate secretion, and inhibiting gastrin-stimulated gastric acid secretion. These effects work together to increase motility. It also has the function of stimulating pepsinogen secretion by chief cells. VIP seems to be an important neuropeptide during inflammatory bowel diseases since the communication between mast cells and VIP in colitis, as in Crohn's disease, is upregulated.

In the heart It is also found in the heart and has significant effects on the cardiovascular system. It causes coronary vasodilation as well as having a positive inotropic and chronotropic effect. Research is being performed to see if it may have a beneficial role in the treatment of heart failure.

In the brain VIP is also found in the brain and some autonomic nerves: One region includes a specific area of the suprachiasmatic nuclei (SCN), the location of the 'master circadian pacemaker'. See SCN and circadian rhythm below. VIP in the pituitary helps to regulate prolactin secretion; it stimulates prolactin release in the domestic turkey. Additionally, the growth-hormone-releasing hormone (GH-RH) is a member of the VIP family and stimulates growth hormone secretion in the anterior pituitary gland. VIP is also expressed in a subtype of inhibitory interneuron in various regions of the brain.

In other areas of the body VIP provokes vaginal lubrication, doubling the total volume of lubrication produced.

Mechanisms VIP binds to both VPAC1 and VPAC2 receptors. When VIP binds to VPAC2 receptors, a G-alpha-mediated signaling cascade is triggered. In a number of systems, VIP binding activates adenyl cyclase activity leading to increases in cAMP concentration and PKA activity. The PKA then activates other intracellular signaling pathways like the phosphorylation of CREB and other transcriptional factors. The mPer1 and mPer2 promoters have CRE domains and thus provides the mechanism for VIP to regulate the molecular clock itself. Then it will activate gene expression pathways such as Per1 and Per2 in circadian rhythm. In addition, GABA levels are connected to VIP in that they are co-released. Sparse GABAergic connections are thought to decrease synchronized firing. While GABA controls the amplitude of SCN neuronal rhythms, it is not critical for maintaining synchrony. However, if GABA release is dynamic, it may mask or amplify synchronizing effects of VIP inappropriately. Circadian time is likely to affect the synapses rather than the organization of VIP circuits.

SCN and circadian rhythm

The SCN coordinates daily timekeeping in the body and VIP plays a key role in communication between individual brain cells within this region. At a cellular level, the SCN expresses different electrical activity in circadian time. Higher activity is observed during the day, while during night there is lower activity. This rhythm is thought to be important feature of SCN to synchronize with each other and control rhythmicity in other regions. VIP acts as a major synchronizing agent among SCN neurons and plays a role in synchronizing the SCN with light cues. The high concentration of VIP and VIP receptor containing neurons are primarily found in the ventrolateral aspect of the SCN, which is also located above the optic chiasm. The neurons in this area receive retinal information from the retinohypothalamic tract and then relay the environmental information to the SCN. Further, VIP is also involved in synchronizing the timing of SCN function with the environmental light-dark cycle. Combined, these roles in the SCN make VIP a crucial component of the mammalian circadian timekeeping machinery. After finding evidence of VIP in the SCN, researchers began contemplating its role within the SCN and how it could affect circadian rhythm. The VIP also plays a pivotal role in modulating oscillations. Previous pharmacological research has established that VIP is needed for normal light-induced synchronization of the circadian systems. Application of VIP also phase shifts the circadian rhythm of vasopressin release and neural activity. The ability of the population to remain synchronized as well as the ability of single cells to generate oscillations is composed in VIP or VIP receptor deficient mice. While not highly studied, there is evidence that levels of VIP and its receptor may vary depending on each circadian oscillation. The leading hypothesis of VIP function points to the neurons using VIP to communicate with specific postsynaptic targets to regulate circadian rhythm. The depolarization of the VIP-expressing neurons by light appears to cause the release of VIP and co-transmitters (including GABA) that can in turn, alter the properties of the next set of neurons with the activation of VPAC2. Another hypothesis supports VIP sending a paracrine signal from a distance rather than the adjacent postsynaptic neuron.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Vasoactive intestinal peptide

Start with the simplest possible case. Write down what Vasoactive intestinal peptide claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Vasoactive intestinal peptide before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Vasoactive intestinal peptide ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Vasoactive intestinal peptide

In research: Vasoactive intestinal peptide appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Vasoactive intestinal peptide in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Vasoactive intestinal peptide is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 6, Hormones of the digestive system, Hormones of the hypothalamic-pituitary-prolactin axis, so understanding it makes those chapters shorter.
In everyday life: Look for Vasoactive intestinal peptide outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Vasoactive intestinal peptide in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vasoactive intestinal peptide means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Vasoactive intestinal peptide out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vasoactive intestinal peptide in simple terms?

Why does Vasoactive intestinal peptide matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Vasoactive intestinal peptide?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Vasoactive intestinal peptide.