Chapter 21 Exercises — Oxytocin and Vasopressin

How to use these. Sections A through F move from recall to construction. Items marked † are the harder ones — they require combining material from more than one section, or from an earlier chapter, or defending a position rather than reporting one. No answers are provided here. Several items have more than one defensible response; what matters is whether your reasoning survives being written down.

Nothing in this chapter or these exercises constitutes medical advice, and no item asks you to construct a protocol, a dose, or a source. If an answer you are drafting starts to look like an instruction sheet, you have misread the question.

Section A — Structure and chemistry

A1. Oxytocin and vasopressin are each how many amino acids long, and at how many positions do they differ? Name the positions and the substitutions.

A2. Both peptides contain a disulfide bridge. Which residues form it, what shape does it create, and which Chapter 1 term describes this kind of link?

A3. Position 8 carries leucine in oxytocin and arginine in vasopressin. Using Chapter 1 §1.2's families of side chains, explain why this is a more consequential swap than the position 3 change.

A4. † Explain the sentence "selectivity is a statement about concentration" without using the words oxytocin or vasopressin. Then give one clinical consequence that follows from it, using them.

A5. Name the four receptors introduced in §21.1, and give the principal tissue and effect for each.

A6. What did du Vigneaud accomplish, in what year was it recognized, and with what prize? State one reason it mattered beyond the two molecules themselves.

Section B — The uncontroversial physiology

B1. Distinguish milk production from milk ejection, and name the hormone principally responsible for each.

B2. Oxytocin receptor density in the myometrium changes across pregnancy. Describe the change and explain why it means that hormone concentration alone does not predict effect.

B3. † The natural oxytocin signal is pulsatile; obstetric administration is a continuous infusion. Using Chapter 3, name two specific ways a receptor system can behave differently under a sustained signal than under a pulsed one, and say which would matter most for prolonged administration.

B4. State the two principal approved obstetric uses of oxytocin, and name the list of essential medicines on which it appears.

B5. † Atosiban blocks the same receptor that oxytocin activates, and is used to suppress preterm labor. Using Chapter 1 §1.8, explain what the shared "-tocin" stem does and does not tell you — and contrast it with a naming pair from that section where the stem does encode direction of action.

Section C — Voles, trust, and replication

C1. What is the behavioral difference between prairie voles and their closely related non-monogamous relatives, and what neuroanatomical difference was found to accompany it?

C2. State in one sentence the general principle the prairie vole work established about how a conserved molecule can produce species-specific behavior.

C3. List three specific conclusions the vole literature cannot support, and say why in each case.

C4. † Rating rule 3 says never upgrade with mechanism. Apply it explicitly to the vole work: name the human claim someone might want to upgrade, name the mechanism they would cite, and state precisely what is wrong with the move.

C5. Describe the trust game paradigm — what each participant does, and what is treated as the measure of trust — then summarize what happened when the finding was subjected to larger and preregistered replication attempts.

C6. † Explain the winner's curse in this context: why small studies of small true effects produce published effect sizes that are systematically too large. Do this without using any numbers.

Section D — Context-dependence and the nickname

D1. State the social salience hypothesis in one sentence.

D2. The chapter says the nickname problem here is worse than exaggeration. Explain what makes it worse, using the word sign.

D3. Name three moderating variables the literature has reported for oxytocin's social effects — variables that can change the direction, not merely the size, of the effect.

D4. † Describe the two competing models from §21.5 (affiliation generator vs. gain on social cues), then state the single observation that the first model has no place to put. Be precise about whether the first model has a wrong parameter value or a missing term.

D5. † Chapter 13 §13.6 made the same argument about ghrelin. Write the general rule that covers both cases in one sentence, then apply it to a third hormone nickname of your choosing and say specifically what the compression loses.

Section E — Delivery, trials, and vasopressin

E1. Why did the field turn to intranasal administration rather than intravenous for behavioral studies?

E2. Describe the proposed nose-to-brain route: which nerve pathways, and what does it bypass?

E3. List four distinct reasons the chapter gives for doubting that intranasal administration delivers behaviorally meaningful amounts of oxytocin to the brain.

E4. † The chapter says the supraphysiological doses used "cut both ways." Give the argument in each direction, and say whether you think they are of equal weight.

E5. † Explain why a positive behavioral result is also compromised by the delivery question, not just a null one — and describe the different way each is ambiguous.

E6. Summarize, directionally and without inventing numbers, the outcome of the large multisite trial of intranasal oxytocin in autism. Then state the framing the chapter insists on before reporting any such result, and explain how that framing changes what a trial's outcome measure is actually measuring.

E7. Name vasopressin's three receptor subtypes and the effect mediated at each. Then describe the two sensor systems that regulate its release, the difference in their sensitivity, and the engineering priority that difference reveals.

Section F — Rating, dossier, and construction

F1. Oxytocin holds a ✅ and three ❌ ratings in this chapter. Explain to someone who thinks that is incoherent why it is not, naming the rating rules involved.

F2. † Distinguish "evidence is absent" from "evidence is present and negative." State why the second is a stronger epistemic position and a worse commercial one, and name one consequence of that asymmetry for the unapproved-compound market.

F3. Write a complete four-line 📊 Evidence Rating block for the claim "intranasal oxytocin improves social functioning in schizophrenia." Include the date stamp.

F4. † Take the claim "oxytocin makes people more generous" and rewrite it three times: once so it could be rated ⚠️, once so it could be rated ❌, and once so it is genuinely unrateable as stated. Explain what you changed each time and why the tier moved.

F5. Fill in Field 6 (Evidence and Rating), including the new CONTEXT DEPENDENCE and METHOD CAVEAT lines, for one peptide already in your dossier. If you cannot complete "what would change it," write one paragraph on what that inability tells you about the state of your own belief.