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Supraclavicular brachial plexus block is a commonly used technique for upper limb anesthesia and analgesia. Recently, ultrasound can visualize the trajectory of the brachial plexus, surrounding fascia and anatomical markers, among which standardized scanning and imaging, needle techniques and drug injection methods gradually formed a precise supraclavicular block technique system. However, the application and promotion of precise supraclavicular blocks are in their infancy, risk of intraneural injection, phrenic paralysis, and lack of block dynamics are still difficult and painful points in clinical anesthesia practice. To improve the anesthesiologists' understanding of these techniques and promote their clinical application, this paper focuses on its anatomical basis, approach, and technical characteristics as well as their application in arthroscopic shoulder surgery. [ABSTRACT FROM AUTHOR]

Aims To investigate the effects of high doses of pentazocine on antinociception induced by a high dose of morphine and the role of the kappa-opioid receptors (KORs) in these effects in mice. Main methods Sixty-six C57BL/6J mice were pretreated with a KOR antagonist, nor-binaltorphimine (nor-BNI) (10 mg·kg − 1 ), or a normal saline placebo. All the mice received a subcutaneous injection of morphine (10 mg·kg − 1 ) 120 min later and different doses of pentazocine (3, 10, 30, 56, 100 mg·kg − 1 ) or a normal saline placebo. A tail pressure test, hot plate test and tail flick test were performed before and at 30, 60, 90 and 120 min after the injection of morphine. Key findings The tail pressure test, hot plate test and tail flick test showed that pentazocine at doses of 10 to 100 mg·kg − 1 , but not at 3 mg·kg − 1 , had significant antagonizing effects on the antinociception induced by high-dose morphine to mechanical and thermal pain, and nor-BNI did not affect antinociception in combination with pentazocine at 10 to 100 mg·kg − 1 and morphine at 10 mg·kg − 1 . Significance High-doses of pentazocine antagonize the antinociception induced by a high-dose of morphine in a dose-dependent manner, and this antagonistic effect is not associated with the activation of KORs. [ABSTRACT FROM AUTHOR]

Shu-jing-huo-xue-tang (SJHXT) (Japanese name: Sokei-kakketu-to), a traditional Chinese herbal medicine composed of 17 crude drugs, has been prescribed over hundreds of years for treatment of chronic pain syndromes. We evaluated if oral SJHXT could suppress neuropathic pain behaviors in rats with chronic constriction injury (CCI) of the sciatic nerve. Materials and methods: (1) Rats received repeated oral SJHXT 0.5 or 1.0g/kg once daily for 14 days starting 24h after CCI surgery, while neuropathic manifestations were evaluated until day 20 post-CCI. (2) Other groups of rats received single oral SJHXT 1.0g/kg on day 14 post-CCI. (3) Additional groups of rats received oral SJHXT 1.0g/kg on day 14 post-CCI, concomitantly with intraperitoneal yohimbine 1mg/kg or methysergide 5mg/kg. Neuropathic manifestations, including mechanical allodynia and thermal hyperalgesia, were evaluated with paw withdrawal responses to increasing mechanical pressure and radiant heat, respectively. Results: Mechanical allodynia and thermal hyperalgesia developed by day 14 post-CCI. Repeated oral SJHXT for 14 days produced anti-allodynic and anti-hyperalgesic effects that outlasted the period of drug administration. Single oral SJHXT on day 14 also produced significant anti-allodynic and anti-hyperalgesic effects, which were inhibited by yohimbine, an alpha-2 adrenoceptor antagonist, but not by methysergide, a serotonin receptor antagonist. Conclusions: Oral SJHXT produced anti-hypersensitivity effects by actions on alpha-2 adrenoreceptors in CCI-neuropathic rats, and chronic oral administration of SJHXT could produce the long-lasting anti-hypersensitivity effects. [Copyright &y& Elsevier]

Abstract: Aim of the study: In this study, we investigated the effects of processed Aconiti tuber (PAT), an oriental herbal medicine, at analgesic doses on acute morphine antinociception in morphine-naïve mice and morphine tolerance in morphine-tolerant mice. Materials and Methods: In acute experiments, mice received subcutaneous (s.c.) morphine (2, 5, or 10mg/kg) and oral distilled water or PAT (0.3, 1.0, or 3.0g/kg). The mechanical nociceptive threshold (MNT) and thermal nociceptive latency (TNL) were measured with the tail pressure test and tail flick test, respectively, before, and at 30, 60, 90, and 120min after s.c. morphine injection. In chronic experiments, mice received s.c. morphine (10mg/kg) and oral distilled water or PAT (0.3, 1.0, or 3.0g/kg) once daily for 11 days. MNT was measured before, and at 60min after, and TNL was measured before, and at 30min after, daily morphine injections on days 1–11. Results: PAT at analgesic doses inhibited the acute antinociceptive effect of morphine dose-dependently in morphine-naïve mice. In contrast, PAT at analgesic doses potentiated the chronic antinociceptive effect of morphine dose-dependently by inhibiting the development of morphine tolerance dose-dependently. These effects of PAT on acute and chronic morphine antinociception were mediated through activation of kappa-opioid receptors. Conclusions: These results indicated that chronic co-administration of PAT at analgesic doses with morphine could provide better-maintained morphine analgesia in a long-term morphine treatment after initial inhibition of acute morphine antinociception for a brief period of time. [Copyright &y& Elsevier]

Abstract: In the previous studies, we demonstrated that an oriental herbal medicine, processed Aconiti tuber (PAT), at subanalgesic doses could inhibit or reverse the antinociceptive tolerance to morphine. In the present study, we compared the effect of PAT, trans-(±)-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidin)cyclohexyl)-benzeneacetamide methane sulfonate hydrate (U50488H), a selective kappa opioid receptor (KOR) agonist, and (−)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine-maleate (MK-801), a N-methyl-d-aspartate (NMDA) receptor antagonist, on the antinociceptive tolerance to morphine in the same experimental condition. Mice received subcutaneous morphine (10mg/kg), and oral PAT at a subanalgesic dose (0.3g/kg for mechanical or 1.0g/kg for thermal test), or intraperitoneal U50488H at a subanalgesic dose (3mg/kg), or MK-801 at a subanalgesic dose (0.1mg/kg) once daily for 14 days. The mechanical nociceptive threshold was measured before, and at 60min by tail pressure testing, and thermal nociceptive latency was measured before, and at 30min by hot plate testing, after daily morphine injections. PAT and U50488H could not only inhibit the development of morphine tolerance but also reverse the already-developed morphine tolerance, while MK-801 could only inhibit the development of morphine tolerance but not reverse the already-developed morphine tolerance, in both mechanical and thermal nociceptive tests. These data suggested that PAT, an indirect-acting KOR agonist, share the common pharmacological property of KOR agonists on morphine tolerance, and that PAT may be superior to some NMDA receptor antagonists which do not reverse already-developed morphine tolerance. [Copyright &y& Elsevier]

Abstract: In the previous studies, we demonstrated that an oriental herbal medicine processed Aconiti tuber (PAT) at subanalgesic doses could inhibit the development of mechanical antinociceptive tolerance to morphine using the tail pressure test. In the present study, we evaluated whether PAT could inhibit thermal antinociceptive tolerance to morphine using the high temperature (55°C) hot plate test. Mice received subcutaneous morphine (10mg/kg), and oral PAT at doses that did not inhibit the hot plate response (0.3, 0.5, 1.0, and 2.0g/kg), once daily for 14 days. The thermal nociceptive latency was measured at 30min after daily morphine injections. Compared with placebo, oral PAT partially and dose-dependently inhibited the development of morphine tolerance in morphine-naïve mice, and reversed already-developed morphine tolerance in morphine-tolerant mice. These data suggested that PAT at subanalgesic doses could dose-dependently inhibit and reverse thermal antinociceptive tolerance to morphine. [Copyright &y& Elsevier]

Abstract: Previously, we found that processed Aconiti tuber (PAT) could inhibit morphine tolerance in mice. In the present study, we investigated mechanisms underlying this effect. Mice received subcutaneous (s.c.) morphine (10mg/kg) and oral PAT at a subanalgesic dose (0.3g/kg), once a day for 12 days. Additional PAT-treated groups received morphine and PAT, at 120min after pretreatment with s.c. clocinnamox mesylate (C-CAM) (0.5mg/kg), or nor-binaltorphimine (nor-BNI) (5mg/kg). The antinociceptive effect was assessed with the tail pressure test, at 60min after the daily s.c. morphine injections were given. In the placebo-treated group, repeated morphine injections caused morphine tolerance, and morphine antinociception was abolished by day 6, whereas in PAT-treated groups, significant antinociception was maintained until day 12, suggesting that PAT inhibited morphine tolerance, thereby sustaining morphine antinociception. C-CAM, a selective mu-opioid receptor (MOR) antagonist, blocked morphine antinociception whereas nor-BNI, a selective kappa-opioid receptor (KOR) antagonist, did not. However, both C-CAM and nor-BNI could block the antinociception maintained by the morphine–PAT combination. Results of the study suggested that chronic treatment with PAT at a subanalgesic dose maintained MOR-mediated morphine antinociception by attenuating development of morphine tolerance, and that this tolerance-attenuating effect of PAT was mediated by KOR. [Copyright &y& Elsevier]

Abstract: Processed Aconiti tuber (PAT) is a herbal medicine that has been widely used as an analgesic since ancient times. We investigated effects of subanalgesic doses of PAT on morphine tolerance in mice. Mice received subcutaneous morphine (10mg/kg) and oral PAT at subanalgesic doses (0.1 or 0.3g/kg), once a day for 7 days. Mechanical nociceptive thresholds were measured using the tail pressure test, at 60min after the daily s.c. morphine injections. In the placebo-treated group, repeated administration of s.c. morphine resulted in development of analgesic tolerance. In the PAT-treated groups, oral PAT attenuated morphine tolerance, dose-dependently. The main ingredient alkaloid of PAT causing its tolerance-attenuating activity was mesaconitine, but other ingredient alkaloids, such as aconitine and hypaconitine, also contributed to this activity. In addition, repeated treatment with PAT could reverse already-developed morphine tolerance. Subanalgesic doses of oral PAT thus can attenuate and reverse morphine tolerance in mice. [Copyright &y& Elsevier]

Hypothermia is highly common in patients undergoing gynecological surgeries under general anesthesia, so the length of hospitalization and even the risk of mortality are substantially increased. Our aim was to develop a simple and practical model to preoperatively identify gynecological surgery patients at risk of intraoperative hypothermia. In this retrospective study, we collected data from 802 patients who underwent gynecological surgery at three medical centers from June 2022 to August 2023. We further allocated the patients to a training group, an internal validation group, or an external validation group. The preliminary predictive factors for intraoperative hypothermia in gynecological patients were determined using the least absolute shrinkage and selection operator (LASSO) method. The final predictive factors were subsequently identified through multivariate logistic regression analysis, and a nomogram for predicting the occurrence of hypothermia was established. A total of 802 patients were included, with 314 patients in the training cohort (mean age 48.5 ± 12.6 years), 130 patients in the internal validation cohort (mean age 49.9 ± 12.5 years), and 358 patients in the external validation cohort (mean age 47.6 ± 14.0 years). LASSO regression and multivariate logistic regression analyses indicated that body mass index, minimally invasive surgery, baseline heart rate, baseline body temperature, history of previous surgery, and aspartate aminotransferase level were associated with intraoperative hypothermia in gynecological surgery patients. This nomogram was constructed based on these six variables, with a C-index of 0.712 for the training cohort. We established a practical predictive model that can be used to preoperatively predict the occurrence of hypothermia in gynecological surgery patients. Clinical trial registration: chictr.org.cn , identifier ChiCTR2300071859. • How can the occurrence of intraoperative hypothermia be predicted before surgery in gynecological surgery patients? • To address this issue, we conducted a multicenter cohort study of 802 patients who underwent gynecological surgery. • A powerful model was established for the early identification of patients prone to intraoperative hypothermia. [ABSTRACT FROM AUTHOR]

Background: Rhomboid intercostal block (RIB) is a new regional anesthesia technique that provides postoperative analgesia for breast surgery and thoracoscopic surgery. The published papers are not yet fully integrated and do not adequately address the impact and safety of the RIB on postoperative pain. Methods: The PubMed, Web of Science and Embase were searched from 2016 to 2021 for all available randomized controlled trials (RCTs) that evaluated the analgesic efficacy and safety of RIB after thoracic surgery and breast surgery. Random and fixed-effects meta-analytical models were used where indicated, and between-study heterogeneity was assessed. The primary outcome was Postoperative Numerical Rating Scale (NRS) scores of patients at rest recorded 0–1, 6–8, 24 h after surgery. The secondary outcomes included rate of postoperative nausea and vomiting (PONV), postoperative fentanyl consumption and presence of complications of the block. Results: From 81 records identified, four studies met our inclusion criteria, including 216 patients (RIB:108 patients; no block: 108 patients). In the primary outcome, RIB group showed significantly lower postoperative NRS at rest at first 0–1 h and 6–8 h (weighted mean difference [WMD] = -1.55; 95% confidence internal [CI] = -2.92 to -0.19; p < 0.05), (WMD = -0. 69; 95% CI = -1.29 to -0. 09; p < 0. 05). And there was no significant difference between groups in NRS at rest at 24 h (WMD = -0.78; 95% CI = -1.64 to -0.08; p = 0.77). Also, RIB group showed significantly lower postoperative NRS of breast surgery and thoracoscopic surgery at 0-1 h (WMD = -3.00; 95% CI = -3.13 to -2.87; p < 0.01), (WMD = -1.08; 95% CI = -1.98 to -0.18; p < 0.05). In the secondary outcome, the analysis also showed RIB group had significant lower of POVN rates (summary relative risk (RR) = 0.212;95%CI = 0.10 to 0.45; p < 0. 01) and the postoperative consumption of fentanyl (WMD = -57.52;95%CI = -106.03 to -9.02; p < 0. 05). Conclusion: This review shows that RIB was more effective in controlling acute pain after breast surgery and thoracoscopic surgery than general analgesia. And it is a trend that RIB may be a kind of effective and safe nerve bock technology and it requires further studies. [ABSTRACT FROM AUTHOR]

Bilateral superficial cervical plexus block (BSCPB) is widely used in thyroid surgery. However, its ability to reduce patients' perioperative pain remains controversial. Therefore, this study aimed to investigate the value of using BSCPB perioperatively for thyroid surgery by conducting a systematic review and meta-analysis of relevant clinical studies. In this systematic review and meta-analysis, we conducted comprehensive searches in the PubMed, Embase, and Cochrane Library databases to collect all randomized controlled trials (RCTs) that used BSCPB for thyroid surgery. The included studies were then analyzed for heterogeneity using the chi-square test, and studies with large heterogeneity were subjected to subgroup or sensitivity analyses. Treatment effects were measured using odds ratio (OR) or weighted mean difference (WMD) and 95% confidence interval (CI). A total of 19 RCTs with 1,365 patients who underwent thyroid surgery (713 and 652 patients in the BSCPB and control groups, respectively) were included in this systematic review. Most of the studies reported that cervical plexus blocks were used preoperatively, and the main drugs used were 0.25–0.75% ropivacaine or bupivacaine. The BSCPB procedure could significantly reduce visual analog scale scores in the immediate (WMD: −1.12, 95% CI: −1.51 to −0.73, P < 0.00001), 6-h (WMD: −1.06, 95% CI: −1.60 to −0.53, P = 0.0001) and 24-h (WMD: −0.87, 95% CI: −1.29 to −0.45, P < 0.0001) postoperative period and also reduce opioid requirements for patients in the post-anesthesia care unit (50.99% vs 72.92%, OR: 0.3, 95% CI: 0.17 to 0.52, P < 0.0001) and in the wards (39.80% vs 59.79%, OR: 0.27, 95% CI: 0.12 to 0.59, P = 0.001). Additionally, BSCPB reduced the incidence of postoperative nausea and vomiting (OR: 0.50, 95% CI: 0.29 to 0.87, P = 0.01). Due to the large heterogeneity, the results only suggest decrease use of intraoperative fentanyl and postoperative morphine in the BSCPB group. The use of BSCPB alleviates of postoperative pain, opioid requirement, and reduces incidence of postoperative nausea and vomiting in patients who have undergone thyroid surgery. More clinical studies are needed for further conclusions. [ABSTRACT FROM AUTHOR]

A correction to the article "Efficacy and Safety of Rhomboid Intercostal Block for Analgesia in Breast Surgery and Thoracoscopic Surgery: A Meta-analysis" that was published in a previous issue is presented.

Background: Ultrasound-guided intertruncal approach (IA) to the supraclavicular block (SB) is recently proposed as a new approach for local anesthetic (LA) injection in terms of the classical approach (CA) at the level of the first rib. The CA-SB has been proven to result in satisfying sensorimotor block, but associate with a high risk of intraneural injection. The aim of this randomized non-inferiority study is to explore whether IA-SB can obtain similar block dynamics, as the CA-SB, but avoiding an intraneural injection during the whole nerve block procedure.Methods: The total 122 patients undergoing elective upper extremity surgery will be randomly allocated to receive either an IA-SB or a CA-SB using a double-injection (DI) technique. In the IA-SB group, a portion of LA (15 mL) is injected accurately to the intertruncal plane between the middle and lower trunks under real-time ultrasound guidance; then, the remaining volume (10 mL) is carefully distributed to the other intertruncal plane between the upper and middle trunks. In the CA-SB group, the DI technique will be carried out as described in Tran's study. The primary outcome is the percentage of patients with a complete sensory blockade at 20 min with a predefined non-inferiority margin of - 5%. The secondary outcomes include the sensory-motor blockade of all 4 terminal nerves, onset times of the individual nerves within 30 min, block-related variables, and adverse events.Discussion: The results will provide sensory-motor blockade-related parameters and safety of the ultrasound-guided intertruncal approach to the supraclavicular block, thereby promoting clinical practice.Trial Registration: Chinese Clinical Trial Registry ChiCTR2000040199 . Registered on 25 November 2020. [ABSTRACT FROM AUTHOR]

Introduction: This prospective study was to investigate the successful rate of intraoperative motor evoked potentials (MEP) monitoring for children (<12 years old) with congenital scoliosis. Materials and methods: A consecutive series of 27 young children (7 girls and 20 boys; from 1 to 11 years old) between September 2007 and November 2009, were enrolled to this study. 12 patients received general anesthesia based on TIVA, induced with propofol 2-4 mg/kg and fentanyl 3-5 µg/kg followed by a continuous infusion of propofol (20-150 µg/kg/min, at mean of 71.7 µg/kg/min). The other 15 patients received combined inhalation and intravenous anesthesia, induced with sevoflurane and fentanyl 3-5 µg/kg and maintained by sevoflurane (0.5-1%). The maintenance of anaesthesia management was performed with stable physiological parameters during surgery. Results: Intraoperative MEP monitoring was successfully performed in all patients, while SEP was successfully performed in 26 of 27 patients. There was no significant difference of successful rates between SEP and MEP monitoring ( P > 0.05). As well, no difference in MEP successful rates was observed in two groups with different anesthetic techniques. No wake-up test and no post-operative neurological deficits occurred in this series of patients. Conclusion: Low dose anesthesia by either TIVA with propofol or sevoflurane-based mixture anesthesia protocol can help the intraoperative spinal cord monitoring to successfully elicit MEP and perform reliable monitoring for patients below 12 years of age. [ABSTRACT FROM AUTHOR]

• The Coronavirus Disease 2019 (COVID-19) outbreak has become an evolving global health crisis. • In the COVID-19 epidemic, researchers found that nearly half of COVID-19 inpatients had comorbidities, with hypertension being the most common comorbidities and more frequently observed in patients with severe COVID-19. • Understanding the immune system changes in primary hypertension and how the immune system interacts with COVID-19 is important. • We synthesize recent advances in our understanding of the relationship between primary hypertension and COVID-19 and its underlying mechanisms, and provide specific treatment guidance for these high-risk groups. The coronavirus disease 2019 (COVID-19) outbreak has become an evolving global health crisis. With an increasing incidence of primary hypertension, there is greater awareness of the relationship between primary hypertension and the immune system [including CD4+, CD8+ T cells, interleukin-17 (IL-17)/T regulatory cells (Treg) balance, macrophages, natural killer (NK) cells, neutrophils, B cells, and cytokines]. Hypertension is associated with an increased risk of various infections, post-infection complications, and increased mortality from severe infections. Despite ongoing reports on the epidemiological and clinical features of COVID-19, no articles have systematically addressed the role of primary hypertension in COVID-19 or how COVID-19 affects hypertension or specific treatment in these high-risk groups. Here, we synthesize recent advances in understanding the relationship between primary hypertension and COVID-19 and its underlying mechanisms and provide specific treatment guidelines for these high-risk groups. [ABSTRACT FROM AUTHOR]

Abstract: Aim of the study: Our previous studies indicated that processed Aconiti tuber (PAT), a traditional Chinese herbal medicine, had antinociceptive effects and inhibitory effects on morphine tolerance by activation of kappa-opioid receptor (KOR). Preclinical studies also demonstrated that KOR agonists functionally attenuate addictive behaviors of morphine, such as conditioned place preference (CPP). Therefore, we hypothesize that PAT may inhibit morphine-induced CPP in rats. Materials and methods: (1) Five groups of rats (n =8 for each group) were alternately subcutaneous (s.c.) injected with morphine 10mg/kg (one group receive normal saline as a control) and normal saline for 8 days and oral co-administrated with distilled water or PAT 0.3, 1.0, or 3.0g/kg daily on days 2–9 during CPP training, respectively. (2) Other four groups of rats were randomly s.c. injected with nor-binaltorphimine (nor-BNI; 5mg/kg) or normal saline (as a control) 120min before alternately s.c. with morphine and normal saline and oral co-administrated with distilled water or PAT 3.0g/kg daily. Each rat was acquired pre-conditioning and post-conditioning CPP data and assayed dynorphin concentrations by radioimmunoassay in rat''s nucleus accumbens (NAc) after CPP training. Results: (1) PAT 1.0 or 3.0g/kg dose-dependently decreased the morphine-induced increase of CPP scores. (2) Nor-BNI completely antagonized the inhibition of PAT on morphine-induced CPP. (3) PAT dose-dependently increased dynorphin content in rats’ NAc after CPP training. Conclusions: (1) PAT dose-dependently inhibited morphine-induced CPP. (2) The inhibition of PAT on morphine-induced CPP was probably due to activation of KOR by increasing dynorphin release in rats’ NAc. [Copyright &y& Elsevier]

The development of antinociceptive tolerance to morphine is one of the major problems in its clinical use. Therefore, exploring effective measures to prevent morphine tolerance is of great clinical relevance. We evaluated whether pentazocine could prevent morphine tolerance in mice. Five groups of male ICR mice received repeated subcutaneous (s.c.) injections of morphine at a high dose (10 mg·kg−1) or saline, concomitantly with s.c. injections of pentazocine at low, subanalgesic doses (0.1, 0.3, or 1.0 mg·kg−1) or saline, respectively, once daily for 14 days. On day 15, mice received co-injections of morphine and pentazocine 120 min after pretreatment with nor-binaltorphimine (5 mg·kg−1), a selective κ-opioid receptor antagonist. The tail pressure threshold was measured before and 60 min after the daily drug co-injections. Repeated s.c. co-injections of morphine and saline resulted in a progressive decrease in morphine-induced antinociception, due to the development of morphine tolerance. Co-injections of pentazocine (0.1, 0.3, and 1.0 mg·kg−1) with morphine potentiated the morphine-induced antinociception dose-dependently by preventing the development of morphine tolerance. Nor-binaltorphimine completely inhibited the chronic antinociception maintained by co-injections of morphine and pentazocine. When chronically co-administered with morphine, pentazocine at low, subanalgesic doses dose-dependently potentiated morphine-induced antinociception in morphine-tolerant mice, through its κ-opioid-receptor-mediated tolerance-preventing activity. Because pentazocine is the only agonist-antagonist analgesic that has an effective oral formulation suitable for chronic administration, the results of the present study warrant clinical trials of pentazocine to assess its tolerance-preventing activity in patients with cancer pain. [ABSTRACT FROM AUTHOR]

Aim of the study: To investigate the effect of processed Aconiti tuber (PAT) administered during or after the time of conditioned place preference (CPP) training on the extinction and reinstatement of morphine-priming CPP in rats. The dynorphin level in rats' nucleus accumbens (NAc) is detected as a target of the Dynorphin/Kappa Opioid Receptor (KOR) system for the possible mechanism. Materials and methods: Eight groups of rats were subcutaneously (s.c.) injected with morphine (10mg/kg) (on days 2,4,6,8) or saline (1ml/kg) (on days 3,5,7,9) alternately for 8 days. Five groups, including groups (Mor + Water, Mor + PAT (1.0/3.0g/kg) (S) and Sal + PAT(1.0/3.0g/kg)), were orally given distilled water or PAT 1.0 or 3.0 g/kg daily on days 1-8 during CPP training while other three groups, including groups (Sal + Water and Mor + PAT (1.0/3.0g/kg)(P), were given distilled water or PAT daily from day 10 until CPP was extinct. Morphine 1mg/kg (s.c.) was used to reinstate the extinct CPP and the CPP scores were recorded. The dynorphin concentration in nucleus accumbens (NAc) was assayed by radioimmunoassay after the last CPP measurement. Results: 1) The CPP extinction shortened in Mor + PAT (1.0/3.0 g/kg) (S) groups but extended in Mor + PAT (1.0/3.0 g/kg)(P) groups. 2) Morphine-priming CPP did not change either in Mor + PAT (1.0/3.0 g/kg) (S) or Mor + PAT (1.0/3.0 g/kg)(P) groups. 3) The dynorphin concentration in NAc increased either in Mor + PAT (1.0/3.0 g/kg)(S) or Mor + PAT (1.0/3.0 g/kg)(P) groups. Conclusions: 1) PAT shortened the extinction from morphine induced CPP when administrated before CPP acquisition, whereas it extended the extinction when administrated after CPP formation. 2) PAT administrated during or after CPP training did not affect morphine-priming reinstatement of morphine induced CPP. 3) Dynorphin/KOR system might be a target to regulate morphine-induced CPP extinction but not reinstatement. Image 1 [ABSTRACT FROM AUTHOR]