It has been demonstrated that analgesia induced by physiological stress (1. 6) and electro-acupuncture (8) may be mediated through an endogenous opioid mechanism. It is also known that acute stressful stimuli cause a concomitant release of ,8-endorphin and adrenocorticotropin (ACTH) from the pituitary gland (4). Both these are peptides derived from a common precursor molecule (7) and the releas...

OBJECTIVE(S) There are many reports about the role of rostral ventromedial medulla (RVM) in modulating stress-induced analgesia (SIA). In the previous study we demonstrated that temporal inactivation of RVM by lidocaine potentiated stress-induced analgesia. In this study, we investigated the effect of permanent lesion of the RVM on SIA by using formalin test as a model of acute inflammatory pai...

It has been recognized that various stressful procedures such as foot shock (1-3), environ mental heat (4), immobilization (4, 5) and fighting (6) produce an analgesic effect in experimental animals. Akil et al. (1) and Chesher and Chan (7) showed that the analgesic effect induced by foot shock stress is antagonized by naloxone, a potent opioid receptor blocker, and suggested the involve ment o...

OBJECTIVES Intracerebroventricular injection of orexin-A (hypocretin-1) antagonist has been shown to inhibit stress-induced analgesia. However the locations of central sites that may mediate these effects have not been totally demonstrated. This study was performed to investigate the role of rostral ventromedial medulla (RVM) orexin receptor 1 in stress-induced analgesia (SIA). MATERIALS AND ...

Introduction: Several researches have reported that stress is able to inhibit the development of morphine tolerance via activating of Hypothalamic-Pituitary-Adrenal (HPA) axis. In the present study we tried to examine the effect of epinephrine, the product of adrenal medulla, on the development of morphine tolerance. Methods: Analgesic tolerance was induced by intrathecal (i.t.) injection of...

The principal theme of our work on the phenomenon of stress-induced analgesia has been that multiple neurochemically and neurohormonally discrete paininhibitory systems exist and that these systems can be selectively activated by a single stressor, inescapable footshock. Some of these stress-activated endogenous mechanisms of analgesia involve opioid peptides, others do not. Similarly, some for...

Recent evidence from our laboratory suggests that the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (dizocilpine) selectively antagonizes non-opioid (i.e. naloxone-insensitive) mechanisms of stress-induced analgesia in mice. For example, we have recently demonstrated that a low dose of MK-801 (0.075 mg/kg, i.p.) antagonizes the non-opioid component of a mixed opioid/non-opioid swim str...

A physiological role for beta-endorphin in endogenous pain inhibition was investigated by targeted mutagenesis of the proopiomelanocortin gene in mouse embryonic stem cells. The tyrosine codon at position 179 of the proopiomelanocortin gene was converted to a premature translational stop codon. The resulting transgenic mice display no overt developmental or behavioral alterations and have a nor...