STRESS AND THE BRAIN FUNCTION COMPLICATIONS

For a long time, researchers suggested that hormones have receptors just in the peripheral tissues and do not gain access to the central nervous system (CNS) (Lupien and Lepage, 2001). 

However, observations have demonstrated the effect of anti-inflammatory drugs (which are considered synthetic hormones) on behavioral and cognitive disorders and the phenomenon called “Steroid psychosis” (Clark et al., 1952). 

In the early sixties, neuropeptides were recognized as compounds devoid of effects on the peripheral endocrine system. However, it was determined that hormones are able to elicit biological effects on different parts of the CNS and play an important role in behavior and cognition (De Kloet, 2000). In 1968, McEven suggested for the first time that the brain of rodents is capable of responding to glucocorticoid (as one of EXCLI Journal 2017;16:1057-1072 – ISSN 1611-2156 Received: May 20, 2017, accepted: July 18, 2017, published: July 21, 2017 1058 the operators in the stress cascade). 

This hypothesis that stress can cause functional changes in the CNS was then accepted (McEwen et al., 1968). From that time on, two types of corticotropic receptors (glucocorticosteroids and mineralocorticoids) were recognized (de Kloet et al., 1999). It was determined that the affinity of glucocorticosteroid receptors to cortisol and corticosterone was about one tenth of that of mineralocorticoids (de Kloet et al., 1999). 

The hippocampus area has both types of receptors, while other points of the brain have only glucocorticosteroid receptors (de Kloet et al., 1999).

 The effects of stress on the nervous system have been investigated for 50 years (Thierry et al., 1968). Some studies have shown that stress has many effects on the human nervous system and can cause structural changes in different parts of the brain (Lupien et al., 2009). 

Chronic stress can lead to atrophy of the brain mass and decrease its weight (Sarahian et al., 2014). These structural changes bring about differences in the response to stress, cognition and memory (Lupien et al., 2009). Of course, the amount and intensity of the changes are different according to the stress level and the duration of stress (Lupien et al., 2009). 

However, it is now obvious that stress can cause structural changes in the brain with long-term effects on the nervous system (Reznikov et al., 2007). Thus, it is highly essential to investigate the effects of stress on different aspects of the nervous system.