L18b: ADH and Oxytocin

what are the two main hormones released by the posterior pituitary?

1. Oxytocin

2. ADH

where are oxytocin and ADH produced?

hypothalamus

what is the structure of ADH and oxytocin?

small peptides

where do oxytocin and ADH enter after release from posterior pituitary?

peripheral circulation

where is ADH and oxytocin stored?

posterior pituitary

when are ADH and oxytocin released?

in response to stimuli detected in the hypothalamic nuclei

what is another name for ADH?

vasopressin

what receptors do ADH act through?

vasopressin type 2 receptors

what is the main stimulus for ADH secretion?

1. increased plasma osmolarity

2. decreased blood pressure

where are vasopressin 2 receptors expressed in the body?

distal and collecting ducts of nephrons in the kidneys

what is the function of ADH?

regulates the kidney’s ability to regulate urine volume and osmolarity; conserves water

what results from ADH?

concentrated urine in low volume

what does oxytocin act through?

G-protein coupled receptors in the myometrium of the uterus and myoepithelial cells of mammary glands

what is the main stimulation of oxytocin?

1. giving birth

2. breastfeeding

what does oxytocin stimulate in the animal?

1. force and frequency of uterine contractions during birth

2. ejection of milk through contraction of myoepithelial cells

where is the pineal gland located?

caudal end of the roof of the third ventricle

what is the function of the pineal gland?

functions as a neuroendocrine transducer to regulate reproductive cycles

what do pinealocytes produce?

melatonin

what is melatonin derived from?

tryptophan

what body systems work together to regulate seasonal breeding?

1. CNS

2. pineal gland

3. hypothalamus

4. pituitary gland

what is the pineal gland innervated by?

autonomic nervous system

what is the pineal gland closely linked to?

suprachiasmatic nucleus (SCN) of the hypothalamus

what stimulates the SCN and what is the response?

• light detected by the eyes

• sends signal to pineal gland to regulate melatonin production

what time is melatonin released?

night

where is melatonin released into?

cerebral spinal fluid

what type of receptors does melatonin have?

G-coupled protein receptors in the hypothalamus

what happens when melatonin binds to its receptors?

modulates GnRH secretion

what type of reproduction cycle do horses have?

long-day breeders

when are horses more likely to mate during the year?

spring and summer when daylight increases

what happens to melatonin in horses during longer days?

melatonin decrease promoting estrus and fertility in horse