contd..

Release of norepinephrine in the amygdala facilitates encoding and retention of emotionally significant events. Hippocampus is another important locus of norepinephrine activity that facilitates learning and memory. It also regulates locomotor activity, mechanisms of pain, sleep and vigilance. Insufficient activity of the norepinephrine system can induce depressive syndrome. Increased activity of the serotonin system and decreased activity of the dopamine and norepinephrine systems of the brain are held responsible for emotionally negative states. The reverse is true for emotionally positive states, that is, increased dopamine and norepinephrine and decreased serotonin activities.
Animal studies show that when norepinephrine is injected to various regions of the brain while memory encoding takes place or shortly after the behavioural training it could enhance memory performance. Epinephrine-norepinephrine ratio is relatively high in fight than in flight condition. Serotonin weakens fight type aggression.

Adrenal cortex
Adrenal cortex secretes corticosteroids such as glucocorticoids (examples— cortisol, cortisone and corticosterone) and mineralocorticoids (example— aldosterone). Corticosterone affects metabolism and prepares for response to stress and exercise Hypersecretion can cause Cushing's syndrome which is characterized by changes in carbohydrate and protein metabolism. Aldosterone regulates sodium, potassium and pH balance.
Congenital adrenal hyperplasia is a genetic disorder caused by 21-hydroxylase deficiency in most cases. It affects adrenal cortex resulting into inadequate synthesis of glucocorticoids and mineralocorticoids. This results into excessive secretion of androgens and the corticotrophin-releasing hormone. Congenital adrenal hyperplasia affects the cognitive profile of the patient such as variations in intelligence quotient. High level of androgens during early developmental stage increases cognitive masculinization in females that gets reflected in the form of decreased interest in maternal behavior, intense aggressive behaviour, and less concern for infants.
The memory of stressful events is better compared to events devoid of emotions. Glucocorticoid level consolidates memory-encoding in both animals and human beings. Low dose of glucocorticoid enhance memory consolidation whereas high dose impairs it.

Prostaglandins
Prostaglandins are local hormones that act on or near their site of synthesis. It is synthesized almost in every tissue of the body, but the prostaglandin system of the kidney is considered the most active systems. It can impair memory. It mediates depression-like behaviour and reduces tendency of social exploration. Besides mediating certain physiological functions, prostaglandins also reconcile sickness behaviour. Hennessy et al. (2007) have reported that the injection of indomethacin to maternally separated guinea pig pups also reduced their passive behaviour. Indomethacin is an inhibitor of prostaglandin synthesis.