Morphine prevents the development of stress-enhanced fear learning

Opioid-dependent regulation of high and low fear responses in two inbred mouse strains

“…These results are consistent with clinical observations and with basic research suggesting the role of morphine treatment in alleviating stress-evoked behavioral symptoms [44,45]. In accordance with others [46], we emphasize that multiple injections of a relatively high dose of morphine is necessary to decrease the freezing behavior. A single injection was insufficient to change the fear response (Suppl.…”

Protective effects of the novel adenosine derivative WS0701 in a mouse model of posttraumatic stress disorder

“…Recent studies have revealed that the opiate analgesic morphine is effective in preventing PTSD in people experiencing physical injuries from traumatic events [26] . Morphine is an opioid receptor agonist, and the mechanism by which opioids can inhibit the development of PTSD may be due to pain relief and the blockade of fear memory consolidation; however, the use of opioids is limited by addiction and abuse problems [27] . Adenosine has been reported to have anxiolytic, sedative, hypnotic and anticonvulsant effects.…”

Stress and opioids: Role of opioids in modulating stress-related behavior and effect of stress on morphine conditioned place preference

“…␤-Endorphin inhibits the CRH release by a negative feedback mechanism, which may also contribute in attenuating stress response. Nixon et al, 2010;Szczytkowski-Thomson et al, 2013). Administration of morphine following a traumatic event reduces the severity of symptoms and the risk of PTSD development (Bryant et al, 2009;Stoddard et al, 2009).…”

“…Numerous research studies and reviews provide evidence for the role of the endogenous opioid system in regulating and modulating the HPA axis, autonomic nervous system and behavioral responses during stress (Valentino and Bockstaele, 2008). Various clinical and preclinical studies have documented the critical role of endogenous as well as exogenous opioids in modulating stress and stress-associated anxiety, posttraumatic stress disorder (PTSD) and depression (Nixon et al, 2010;Szczytkowski-Thomson et al, 2013). Furthermore, stress has also been shown to modulate the response of opioids, including drug craving and reinstatement of drug of abuse (Hays et al, 2012;Haghparast et al, 2013).…”