biology

Vasotocin

Vasotocin 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 Vasotocin rather than just read about it. In short: Vasotocin is an oligopeptide homologous to oxytocin and vasopressin found in all non-mammalian vertebrates (including birds, fishes, and amphibians) and possibly in mammals during the fetal stage of development. Arginine vasotocin (AVT), a hormone produced by neurosecretory cells within the posterior pituitary gland (neurohypophysis) of the brain, is a major endocrine regulator of water balance and osmotic homeostas…

Key takeaways

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

Reference excerpt

Vasotocin is an oligopeptide homologous to oxytocin and vasopressin found in all non-mammalian vertebrates (including birds, fishes, and amphibians) and possibly in mammals during the fetal stage of development. Arginine vasotocin (AVT), a hormone produced by neurosecretory cells within the posterior pituitary gland (neurohypophysis) of the brain, is a major endocrine regulator of water balance and osmotic homeostasis and is involved in social and sexual behavior in non-mammalian vertebrates. In mammals, it appears to have biological properties similar to those of oxytocin (stimulating reproductive tract contraction as in egg laying or birth) and vasopressin (diuretic and antidiuretic effects). It has been found to have effects on the regulation of REM sleep. Evidence for the existence of endogenous vasotocin in mammals is limited and no mammalian gene encoding vasotocin has been confirmed. AVT (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Arg-Gly-NH2), which occurs in the lamprey, represents the ancestral form in the phylogeny of the vertebrate neurohypophysial hormones. Gene duplication and point mutation have produced two distinct lineages, one involved in reproduction (oxytocin-like peptides) and the other in osmoregulation (vasopressin-like peptides). These hormones have remained highly conserved throughout evolution. Each is a peptide of nine amino acids derived from a preprohormone precursor by proteolytic cleavage, with an intramolecular disulfide bridge between the cysteine (Cys) residues; the C-terminal glycine (Gly) residue is amidated. Six of the residues have been found to be invariant in homologous peptides from numerous species of vertebrates. The vasopressin-like peptides, which differ in positions 3 and/or 8, include AVT and the mammalian hormones arginine vasopressin (Cys-Tyr-Phe-Gln-Asn-Cys-Pro-Arg-Gly-NH2, with isoleucine-3 of AVT changed to phenylalanine) and lysine vasopressin (isoleucine-3 changed to phenylalanine and arginine-8 changed to lysine). The oxytocin-like peptides, which differ in positions 4 and/or 8, include oxytocin (Cys-Tyr-Ile-Gln-Asn-Cys-Pro-Leu-Gly-NH2, with arginine-8 of AVT changed to leucine), mesotocin (arginine-8 changed to isoleucine), and isotocin (glutamine-4 changed to serine and arginine-8 changed to isoleucine); they differ from the vasopressin-like peptides in having a neutral amino acid in place of a basic amino acid at position 8. Oxytocin occurs in placental mammals; mesotocin occurs in amphibians, reptiles, and birds, and isotocin occurs in fishes.

Biosynthesis AVT is synthesized as a preprohormone that includes a second peptide, neurophysin VT (neurophysins are carrier proteins that are secreted along with their passenger hormones); intracellular proteolytic processing generates the mature peptides. In the chicken (Gallus gallus), the 161-amino acid vasotocin-neurophysin VT preprohormone is encoded by the gene AVP, which is considered homologous to the mammalian genes encoding arginine vasopressin. Removal of the 19-amino acid N-terminal signal peptide generates the prohormone, which is hydrolysed to AVT (derived from amino acids 20–28) and neurophysin VT (derived from amino acids 32–161). The existence of two AVT preprohormones with different sequences in fishes (such as chum salmon, Oncorhynchus keta) is evidence for gene duplication.

Physiological effects AVT combines both antidiuretic and reproductive activities similar to those of oxytocin and vasopressin. The physiological actions of AVT in birds are mediated through diverse receptor subtypes VT1, VT2, VT3 and VT4. AVT and synthetic analogs injected into monkeys cause reabsorption of osmotically free water and changes in excretion of sodium and potassium ions in the kidneys. AVT produces distinct effects on the reproductive functions of male and female domestic chickens. In laying hens, AVT synthesised in magnocellular diencephalic neurons is released into circulation in a highly coordinated manner, contributing to the peripheral control of oviposition. In males, parvocellular AVT cells located in the limbic system (bed nucleus of stria terminalis) express AVT. This expression is sensitive to gonadal steroids and is correlated with sexual differentiation of masculine behavior such as courtship vocalization and copulation.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Vasotocin

Start with the simplest possible case. Write down what Vasotocin 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 Vasotocin 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 Vasotocin 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 Vasotocin

In research: Vasotocin 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 Vasotocin 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: Vasotocin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Neuropeptides, Nonapeptides, Oxytocin receptor agonists, so understanding it makes those chapters shorter.
In everyday life: Look for Vasotocin 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 Vasotocin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vasotocin 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 Vasotocin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vasotocin in simple terms?

Why does Vasotocin 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 Vasotocin?

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 Vasotocin.