Monoamine oxidase is found in nearly all tissues and exists in two similar molecular forms coded by separate genes. MAO-A has a substrate preference for

and is the main target for drugs. Used less frequently than

due to dietary and drug interactions. Used to treat

depression and social phobia (short-acting drugs)

TCAs are highly

bound. This means they have a large volume of distribution and

elimination. They are metabolised in the liver by 2 main routes: N-

and ring

Both metabolites are still active and the plasma concentration of these metabolites is comparable to that of the

drug. The drugs are inactivated by

conjugation of the hydroxylated metabolites.

Show selectivity with respect to 5-HT over

Less likely to show

effects than TCAs and less dangerous in overdose. Similar in efficacy and time course to

TRH is a small tripeptide (Glu-His-Pro) that is secreted from supraoptic and paraventricular nuclei of the

Its secretion is inhibited by T3, T4 and

It has a half life of

TRH promotes pituitary

TSH

(and prolactin) production and secretion.

The normal response is that stress causes the hypothalamus to secreted more

releasing hormone (CRH), which acts on the

posterior and causes it to secrete more ACTH -

hormone. ACTH acts on the adrenal

and stimulates it to release more cortisol. Cortisol helps you cope with stress - fight or flight preparation. The axis has a strong

feedback system. In depression, cortisol levels are

especially when it show normally trough - normally highest at night and early morning.