Despite the central role of general anesthesia in modern healthcare, the frequency of anesthesia-related morbidity resulting from the toxicity and non-specificity of anesthetic drugs remains high. Among the key behavioral states of general anesthesia is antinociception (reduced sensitivity to pain). Within the nociceptive pathway in the brain and the central nervous system, the periaqueductal g...

It has been shown that GABAA receptor blockade in the dorsomedial and ventromedial hypothalamic nuclei (DMH and VMH, respectively) induces elaborated defensive behavioural responses accompanied by antinociception, which has been utilized as an experimental model of panic attack. Furthermore, the prelimbic (PL) division of the medial prefrontal cortex (MPFC) has been related to emotional reactio...

Rats exposed to an elevated plus maze (EPM) with four open arms display antinociception while on the maze and hyperalgesia immediately upon removal. Little is known about the neural mechanisms underlying EPM-induced antinociception and the subsequent hyperalgesia except that the antinociception is not mediated by endogenous opioids. The objective of the present study was to test the hypothesis ...

Ingestion by rats of rat placenta or amniotic fluid enhances opioid-mediated, or partly opioid-mediated, antinociception produced by morphine injection, vaginal or cervical stimulation, late pregnancy, and foot shock. This phenomenon is believed to be produced by a placental opioid-enhancing factor (POEF). Ingestion by rats of human or dolphin placenta has also been shown to enhance opioid anti...

Chloramphenicol, an in vitro inhibitor of the glucuronidation of morphine to its putative antianalgesic metabolite, morphine-3-glucuronide (M3G), was coadministered with morphine in adult male Sprague-Dawley rats to determine whether it inhibited the in vivo metabolism of morphine to M3G, thereby enhancing morphine antinociception and/or delaying the development of antinociceptive tolerance. Pa...

Although 5-HT has been implicated in cholestatic itch and antinociception, two common phenomena in patients with cholestatic disease, the roles of 5-HT receptor subtypes are unclear. Herein, we investigated the roles of 5-HT receptors in itch and antinociception associated with cholestasis, which was induced by common bile duct ligation (BDL) in rats. 5-HT-induced enhanced scratching and antino...

The effect of the &selective agonist [D-Pen2,D-PenS]enkephalin (DPDPE) on the antinociception produced by intracerebroventricular (i.c.v.) administration of the # agonists morphine, [D-Ala2,NMePhe4,Gly-olS]enkephalin (DAGO), [NMePhe3,D-Proa]morphiceptin (PLO17), fl-endorphin, phenazocine, etorphine and sufentanil was studied in mice. Only the antinociceptive effects of morphine and normorphine ...

Ingestion by rats of rat placenta or amniotic fluid enhances opioid-mediated, or partly opioid-mediated, antinociception produced by morphine injection, vaginal or cervical stimulation, late pregnancy, and foot shock. This phenomenon is believed to be produced by a placental opioid-enhancing factor (POEF). Ingestion by rats of human or dolphin placenta has also been shown to enhance opioid anti...

Two separate lines of evidence suggested the present study. First, intracerebroventricularly (i.c.v.) administered morphine (a μ-opioid receptor agonist) and β-endorphin (an ε-opioid receptor agonist) produce antinociception by activating different descending pain inhibitory systems. Second, γ-irradiation attenuates the acute antinociceptive action of i.c.v. injected morphine, but not DPLPE (a ...

To obtain benzomorphans with a longer duration of action that may be potential therapeutics for treating cocaine abuse, 8-carboxamidocyclazocine was synthesized. The pharmacological properties of 8-carboxamidocyclazocine were compared with the parent compound cyclazocine. Changing the 8-hydroxyl group on cyclazocine to an 8-carboxamido group resulted in only a 2-fold decrease in the affinity of...