Chapter3 The Hypothalamus and Pituitary Part I The Hypothalamus and Posterior Pituitary

Reference - Textbook

Reference – Course Website 3

Content Introduction Oxytocin Vasopressin

INTRODUCTION

Anatomical and Functional Connection Between the Hypothalamus and Pituitary 6 hypophyseal portal system Hypothalamo hypophyseal tract

Case: Mr. Jones, a 30-year-old man 6 weeks earlier – began passing a lot of urine Once or twice per hour Full bladder four or five times during the night – Unusually thirsty Constantly drinking water Urine was very pale in recent weeks – Headaches at night or waking – Forgetful – Erection dysfunction

Case: Mr. Jones, a 30-year-old man Test at GP (General Physician) – Urine test No protein, no glucose – Blood test Glucose and calcium level normal Test at endocrine clinic – Looked uncomfortable – Dehydrated with a dry mouth and tongue – Body Temperature normal – Resting pulse rate: 100 b.p.m. – Blood pressure: 105/65 mmHg – Fundoscopy: optic nerve to be swollen in both eyes – Visual field test: loss of vision in both temporal (outer) halves of the field – Memory problem: Confuse and could not remember how he had got to the hospital or what he eaten that day Knew the name of his girlfriend and could remember distant events

Visual Field Defect

Oxytocin and Vasopressin The Hormone of the Posterior Pituitary Small peptides – nine amino peptide – Seven of them are common Synthesized in the hypothalamus by magnocellular neurons Action potential initial release in the nerve

11 Synthesis and Release of Vasopressin and Oxytocin

OXYTOCIN

Role of Oxytocin (OXT) Effect on mammary glands. – Cause the contraction of the myoepithelial cells --- milk ejection – Unconditioned and conditioned reflex Effect on uterus – stimulate the smooth muscle contraction, especially that towards the end of gestation. – at least partially responsible for causing birth of the baby 13

14 OXYTOCIN

Oxytocin Release: Neuroendocrine Reflex 15

Clinical Use Oxytocin – Induce labor – Increase uterine contractions during labor – Reduce postpartum bleeding after labor Atosiban: the antagonist of oxytocin receptor – Treatment of the preterm labor

17 Recent Work about Oxytocin Oxytocin Behavior Hormone Cardiovascular Hormone Gastrointestinal Hormone?

VASOPRESSIN (ADH)

Roles of ADH Antidiuretic effect Pressure effect – constricting the arterioles everywhere Neurotransmitter 19

20 Vasopressin Receptors V 2 -receptor: collecting duct Vascular endothelial cells V 1(a) -receptor: vascular smooth muscle V 3(1b) receptor: neurons (in CNS and ENS) Corticotropin cells (in pituitary gland)

Disorders of Vasopressin Deficiency – Caused by a tumour or trauma of the brain – Diabetes inspidus (hypothalamic or cranial) – Polyuria – large volumes of very dilute urine – Polydipsia ( 烦渴） - excessive thirst – Treatment: Desmopressin – a synthetic analogue of vasopressin

Disorders of Vasopressin Excess – Causes: Neoplasm-Lung cancer Neurological disease – meningitis ( 脑膜炎） Lung disease – pneumonia and tuberculosis Prescribed drug – carbamazepine （立痛定） – Syndrome of inappropriate ADH (SIADH) Urine more concentrated Hyponatraemia – Headache, nausea, vomiting, confusion, coma

Clinical Use of Vasopressin To teat the diabetes insipidus Reduce bleeding during gastrointestinal surgery Boost factor VIII concentration in mild haemophilia

Explanation of Mr. Jones’ Syndromes and Signs 6 weeks earlier – began passing a lot of urine – Unusually thirsty in recent weeks – Headaches at night or waking – Forgetful – Erection dysfunction

Explanation of Mr. Jones’ Syndromes and Signs Test at endocrine clinic – Looked uncomfortable – Dehydrated with a dry mouth and tongue – Body Temperature normal – Resting pulse rate: 100 b.p.m. – Blood pressure: 105/65 mmHg – Fundoscopy: optic nerve to be swollen in both eyes – Visual field test: loss of vision in both temporal (outer) halves of the field – Memory problem