ß-endorphins as Possible Markers for Therapeutic Drug Monitoring

This study was performed in order to investigate possible role of brain beta-endorphins as markers of antidepressive drugs therapy monitoring. Experiment was done using amitriptyline and trazodone as antidepressants. For quantification of brain beta-endorphins we used RIA technique. Our results showed significant decrease of brain beta-endorphins concentration in drug-pretreated animals, vs. those in of control group treated with 0,95% NaCl. The lower values were obtained in trazodone pre-treated animals. This study shows that use of psychoactive drugs have influence on brain beta-endorphins concentration. beta-endorphins could be of great importance, used as markers for evaluation of patient treatment.


Introduction
The investigations of relation between endorphins and depression began with fi ndings of enkephalin and opioid receptors located in mood-response areas of the brain.Previous research raised a question whether excess, defi ciency, or static levels of endorphins cause depression.Also, it was hypothesized that endorphins may not be a factor in depression at all.Th erefore, it was presumed that it is premature to conclude how the endogenous opioid system is involved in depression.Endorphins are likely to modulate the nervous system activity over the long-term rather than short time period.Endorphins are released in shock, freeze, "fight or flight", trauma, physical pain and in all stress including psychological stress.They serve as an analgesic (pain killing), anesthetic and cause dissociation, immobilization and loss of self.Depressives induce elevation of stress hormone levels in blood.Since endorphins are released along with ACTH in response to any stressor, depressives are supposed to "elevate" endorphin levels as well (,).
ANTIDEPRESSANT DRUGS Th ere are numerous antidepressant medications, which are specifi cally designed to mimic the eff ects of endorphins in the brain to make a depressed person feel better or cope with stressful situations.Because of stimulated production of endorphins, studies have shown that physical activity can have a similar eff ect as antidepressants.But unlike antidepressants, there are no negative physiological side eff ects of exercise.Antidepressants can also take between two and three weeks before showing the improvement of eff ects, whereas exercise can boost your mood instantly.Investigations in the field of psychopharmaceutical drugs gave us a lot of knowledge about their positive and side eff ects.Tricycle antidepressants were fi rst in use, expressing their eff ects as a supplement for primary role -inhibition of norepinephrin and serotonin uptake by the nervous ends (, ).More recently, practice patterns have shifted to the antidepressant class as the most commonly prescribed for anxiety disorders.Th is is due to their proven effi cacy in anxiety as well as in commonly co-morbid depressive symptoms.Although efficacy between the selective serotonin reuptake inhibitors (SSRIs) and the tricyclic antidepressants (TCAs) is similar, the SSRIs have an enhanced safety and tolerability profi le, making them the preferred agent for all anxiety disorders ().Th e effi cacy of each antidepressant available has been found equal to that of amitriptyline in double-blind studies as far as mild to moderate depression is involved.However, it seems that some antidepressants are more eff ective than others in the treatment of severe types of depression ().Th e considerable side eff ect burden, the possibility of producing anticholinergic delirium, and their contribution to promoting falls and hip fractures, make TCAs especially unsuitable for the elderly and no longer recommended.SSRIs have been proved to relieve many of the anxiety and/or depressive symptoms associated with anxiety disorders, such as generalized anxiety disorder (GAD), social anxiety disorder (SAD), panic disorder, obsessive-compulsive disorder (OCD), and post-traumatic stress disorder (PTSD).Th ey are eff ective, well tolerated, and relatively safe in overdose situations, making them an ideal choice for the treatment of anxiety, particularly for the elderly population.Although the majority of SSRIs have gained US Food and Drug Administration (FDA) approval for major depressive disorder, they may not be interchangeable in the treatment of anxiety disorders, because each SSRI has diff erent FDA approvals for the anxiety disorders ().Trazodone, nefazodon and bupropion has less defi ned neuropharmacology and are taken as atipic.Nevertheless, they have better effi ciency and endurance, leading to better acceptance.Trazodone is an eff ective antidepressant drug with a broad therapeutic spectrum, including anxiolytic effi cacy.Th is triazolopyridine antidepressant, is currently the second most commonly prescribed agent for the treatment of insomnia due to its sedating qualities.Given trazodone's widespread use, a careful review of the literature was conducted to assess its effi cacy and side eff ects when given for treatment of insomnia.Although trazodone is usually referred to as a serotonin (-HT) reuptake inhibitor, this pharmacological eff ect appears to be too weak to fully account for its clinical eff ectiveness (, ).
ANTIDEPRESSANTS AND Β-ENDORPHINS Previous investigations showed that acute amitriptyline and clomipramine produce naloxone-reversible antinociception.Th is apparent opioid-like involvement was further investigated by measuring β-endorphin levels in the hypothalamus following acute and chronic treatment with these antidepressants.Th ey demonstrated signifi cantly raised levels of β-endorphin.Th e support was provided for the suggestion that antidepressants   BOSNIAN JOURNAL OF BASIC MEDICAL SCIENCES 2007; 7 (1): 11-14 RADIVOJ JADRIĆ ET AL.: β-ENDORPHINS AS POSSIBLE MARKERS FOR THERAPEUTIC DRUG MONITORING activate opioid systems, through both a direct opioid receptor interaction and an indirect action through enhanced release of opioid peptides.Moreover, it is postulated that the direct action of antidepressants on opioid receptors and the endogenous opioid peptides released interact as agonists at both μ-and δ-opioid receptors to inhibit nociceptive transmission, since the activity is antagonized by both naloxone and naltrindole ().Research showed synergistic infl uence of trazodone, combined with mud bath in therapy of fi bromyalgic syndrome, bettering psychological response of homeostasis formation and systems as an answer to stress.Desipramine and paroxetin, used in animal depression models did not signifi cantly aff ect the extracellular levels of β-endorphins in nucleus accumbens, but chronic antidepressant treatment did normalize serotonin-induced release of β-endorphins, as well as behavioral manifestation of depressive behaviour (, ).

Material and Methods
Albino Wistar rats, weight  g were used, divided in groups of , with each animal control to itself.Ethical Committee of our Institution approved the experiment.Amitriptyline (mg/kg/day) and trazodone (mg/kg/day) were administrated to experimental, and , NaCl solution to control group.Before brain samples were collected, all animals were properly sacrifi ced.Collection of brain samples was performed immediately for control group, and after st and th day of amitriptyline and trazodone administration in treated animals.For analyzing β-endorphin levels we used RIA technique, for quantifi cation of human serum and brain β-endorphin (Nichols Institute, San Juan, Capistrano, USA), and for radioactivity level β-counter with gamma-radiation source (LKB Wallac -Sweden).β-endorphin concentration is directly proportional to radioactivity measured in samples.Concentration is given in pg/g for brain β-endorphin values.Counting mean value, standard deviation and standard error we performed statistic evaluation of obtained results.Th e level of signifi cance was determined by use of Student's T test, with values p≤, considered as significant.

Results and Discussion
Our data, presented by charts and graphics, show brain βendorphins values after st and th day of antidepressive drug administration.Obtained values for each day were compared to the other, and to those of control group.
Our results are different compared to results of other authors ().After st day results show significant decrease of brain β-endorphins, which was present also in rat brains after th day of continuous antidepressant administration.In general, amitriptyline produced greater response considering higher brain β-endorphins concentration compared to trazodone.There was significant difference between brain β-endorphins values of animals treated with trazodone compared with amitriptyline group after st day of treatment.There was no significant difference between rat brain β-endorphins in other compared groups/days, showing lower values of brain β-endorphins concentration on each day of continuous tra-zodone versus amitriptyline administration (chart ).Individual values for each animal of experimental groups are presented in Graphic .Our results show mostly lower brain β-endorphins values of animals treated with trazodone.Th ose diff erences may be dependent to lower brain β-endorphins values before beginning of treatment.We consider that all of these changes can be caused by diff erences in mechanism of triazolopyridine (trazodone) and tricyclic antidepressant drugs action on brain β-endorphins content.Th at points at possible diff erences in synthesis intensity of β-endorphins, degradation of brain β-endorphins and possible releasing into blood stream, caused by constant antidepressive drugs administration.

Conclusion
-Rat brain β-endorphins values after a continuous antidepressive drugs treatment are signifi cantly lower then those in control group -In general, amitriptyline produced greater response considering higher brain β-endorphins concentration.
-Values of rat brain β-endorphins in trazodone pretreated animals are lower compared to values of amitriptyline treated groups -Evaluation of brain β-endorphins level could be used as markers for investigation of psychoactive drug eff ects