Morphine is a natural opioid which is used in medicine due to his potent analgesic and sedative effects. In the forefront of scientific interest is a chronic usage of opioids which can lead to a development of drug addiction. Morphine role in oxidative stress was described in last years. It was revealed its protective potencial by many studies. However, some studies described its pro-oxidative effect. The aim of this study was to determinate effect of chronic morphine on cell survival after oxidative stress caused by H202 analog - tBHP in the SH-SY5Y neuroblastoma cell line. The results verified morphine protective effect against oxidative stress. The highest protective effect of morphine was achieved in a concetration of 10 µM. It was desribed that morphine can induce activation of mu-opioid (MOR) and Toll-like 4 (TLR4) receptors signalling pathway on molecular level. The aim of this thesis was to evaluate the role of MOR a TLR4 in protective effect of morphine against oxidative stress by two methods. Firstly, it was used tests of oxidative stress on cell viability. The obtained results demonstrated majority role of TLR4 and minory role of MOR. Afterwards, we assesed changes in the expression of MOR a TLR4 after chronic morphine by SDS-PAGE electrophoresis. Results of these experiments did not...