Nicotine addiction is a concern worldwide. Most mechanistic investigations are on nicotine substance dependence properties based on its pharmacological effects. However, no effective therapeutic treatment has been established. Nicotine addiction is reinforced by environments or habits. We demonstrate the neurobiological basis of the behavioural aspect of nicotine addiction. We utilized the conditioned place preference to establish nicotine-associated behavioural preferences (NABP) in rats. Brain-wide neuroimaging analysis revealed that the medial prefrontal cortex (mPFC) was activated and contributed to NABP. Chemogenetic manipulation of µ-opioid receptor positive (MOR⁺) neurons in the mPFC or the excitatory outflow to the nucleus accumbens shell (NAcShell) modulated the NABP. Electrophysiological recording confirmed that the MOR⁺ neurons directly regulate the mPFC-NAcShell circuit via GABA_A receptors. Thus, the MOR⁺ neurons in the mPFC modulate the formation of behavioural aspects of nicotine addiction via direct excitatory innervation to the NAcShell, which may provide new insight for the development of effective therapeutic strategies.
Animals ; Nucleus Accumbens/drug effects* ; Prefrontal Cortex/drug effects* ; Nicotine/pharmacology* ; Receptors, Opioid, mu/metabolism* ; Male ; Rats ; Rats, Sprague-Dawley ; Tobacco Use Disorder/metabolism* ; Neurons/drug effects* ; Neural Pathways/drug effects*

OBJECTIVE: To observe the effect of early intervention of bone-nearby acupuncture (BNA) combined with electroacupuncture (EA) on the expression of histone deacetylase1(HDAC1), histone deacetylase 2 (HDAC2) andμ-opioid recepter (MOR) in dorsal root ganglia (DRG) of bone cancer pain-morphine tolerance (BCP-MT) rats, and to explore its possible mechanism. METHODS: A total of 35 SD rats were randomized into a sham BCP group (=6), a BCP group (=7), a MT group (=7), a BNA+EA group (=8) and a shame BNA group (=7). Except of the sham BCP group, cancer cell inoculation operation at left tibia was given in the other 4 groups to establish the bone cancer pain model. In the MT group, the BNA+EA group and the shame BNA group, intraperitoneal injection of morphine hydrochloride was given to establish the morphine tolerance model. After the operation, bone-nearby acupuncture combined with electroacupuncture was applied at "Zusanli" (ST 36) and "Kunlun" (BL 60) in the BNA+EA group, with dilatational wave, 2 Hz/100 Hz in frequency, 0.5 to 1.5 mA in intensity. Intervention in the shame BNA group was applied at the same time and acupoints as those in the BNA+EA group, the needles were pierced the skin without any electrical stimulation. The needles were retained for 30 min, once a day for continuous 7 days in both BNA+EA and shame BNA groups. Before and 10, 11, 15, 22 days after the operation, the left paw withdrawal threshold (PWT) was measured in the 5 groups. The levels of HDAC1, HDAC2 and MOR in DRG were detected by Western blot. RESULTS: Ten days after the cancer cell inoculation operation, the PWT of the BCP, MT, BNA+EA and sham BNA groups was decreased compared with the sham BCP group (<0.01). Eleven days after the operation, the PWT of the MT, BNA+EA and sham BNA groups was increased compared with the BCP group (<0.01). Twenty-two days after the operation, the difference was no significant between the BCP group and MT group (>0.05); the PWT of the BNA+EA group was increased compared with the MT and sham BNA group (<0.01). In the BCP group, the DRG levels of HDAC1 and HDCA2 were increased, while the level of MOR was decreased compared with the sham BCP group (<0.05, <0.01). In the MT group, the DRG level of HDAC1 was increased compared with the BCP group (<0.05). In the BNA+EA group, the DRG level of HDAC1 was decreased compared with the MT group and the sham BNA group (<0.01, <0.05), while the level of MOR was increased (<0.01). CONCLUSION Early intervention of bone-nearby acupuncture combined with electroacupuncture can relieve the morphine tolerance in bone cancer pain rats, it may relate to down-regulating the expression of HDAC1 and up-regulating the expression of MOR in the dorsal root ganglia.
Acupuncture Points ; Animals ; Bone Neoplasms ; complications ; Cancer Pain ; therapy ; Drug Tolerance ; Electroacupuncture ; Ganglia, Spinal ; metabolism ; Histone Deacetylases ; metabolism ; Morphine ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; metabolism

Substantial evidence has suggested that deep brain stimulation of the cuneiform nucleus has become a remarkable treatment option for intractable pain, but the possible mechanism is poorly understood. Using a melanocortin-4 receptor (MC4R)-green fluorescent protein (GFP) reporter knockin mouse, we showed that a large number of MC4R-GFP-positive neurons were expressed in the cuneiform nucleus. Immunofluorescence revealed that approximately 40%-50% of MC4R-GFP-positive neurons expressed mu opioid receptors, indicating that they were opioidergic signaling. Our findings support the hypothesis that MC4R expression in the cuneiform nucleus is involved in the modulation of opioidergic signaling.
Animals ; Gene Expression Regulation ; Gene Knock-In Techniques ; Genes, Reporter ; Green Fluorescent Proteins ; genetics ; metabolism ; Mice ; Mice, Transgenic ; Microtomy ; Midbrain Reticular Formation ; cytology ; metabolism ; Neurons ; cytology ; metabolism ; Receptor, Melanocortin, Type 4 ; genetics ; metabolism ; Receptors, Opioid, mu ; genetics ; metabolism ; Recombinant Fusion Proteins ; genetics ; metabolism ; Signal Transduction

OBJECTIVE: To determine the changes of Mu-opioid receptor (Mor) and neuron-restrictive silencer factor (NRSF) in periaquductal gray (PAG) in mouse models of remifentanil-induced postoperative hyperalgesia. METHODS: Thirty-two Kun-Ming mice were randomly divided into 4 groups (8 mice in each group): Group C (mice underwent a sham procedure and saline was infused subcutaneously over a period of 30 min), Group I (mice underwent a surgical incision and the same volume of saline), Group R (mice underwent a sham procedure and remifentanil was infused subcutaneously at the moment of surgical incision over a period of 30 min), and group IR (mice underwent a surgical incision and remifentanil). Paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) tests were performed 24 h before the operation and 2, 6, 24, and 48 h after the operation. The specimens were collected after behavioral testings at 48 h. The expressions of Mor and NRSF in mice's PAG neurons were determined by Western blot. RESULTS: Mechanical allodynia and thermal hyperalgesia developed in Group I, R and IR (P<0.01). Intraoperative infusion of remifentanil enhanced mechanical allodynia and thermal hyperalgesia in mice with planta incision (P<0.01). In Group R and Group IR, the expression of Mor was significantly lower (P<0.01) and NRSF was significantly higher (P<0.01) when compared with Group C and Group I. CONCLUSION Intraoperative infusion of remifentanil induces postoperative hyperalgesia in mouse models, accompanied with decreased expressions of Mor and increased of NRSF level in PAG neurons, which may be involved in remifentanil induced hyperalgesia.
Animals ; Disease Models, Animal ; Hyperalgesia ; chemically induced ; Mice ; Pain, Postoperative ; Periaqueductal Gray ; drug effects ; metabolism ; Piperidines ; administration & dosage ; Receptors, Opioid, mu ; metabolism ; Remifentanil ; Repressor Proteins ; metabolism

OBJECTIVETo observe the effects of Jingqianping Granule (JG) on mRNA and protein expressions of mu opioid receptor in the parietal cortex and the frontal cortex, the hypothalamus and hippocampus of premenstrual syndrome (PMS) Gan-qi invasion rats.

METHODSTwenty rats were selected to prepare the PMS Gan-qi invasion model. After modeling rats were divided into the model group and the Chinese herb treated group, ten in each group. Another 10 rats were selected as the normal control group. During the modeling, JG (1.6 g/kg) was given to rats in the Chinese herb treated group by gastrogavage, while equal volume of normal saline (1 mL/100 g) was given to rats in normal control group and the model group. All treatment was performed once daily for five successive days. The mRNA and protein expressions of mu opioid receptor in the parietal cortex and the frontal cortex, the hypothalamus and hippocampus were detected using RT-PCR and Western blot respectively.

RESULTSCompared with the normal control group, the bands of products of MOR mRNA and protein in the parietal cortex and the frontal cortex were relatively weaker in the model group, and the optical density value decreased. The MOR mRNA and protein expressions in the parietal cortex and the frontal cortex relatively decreased. But the bands of products of MOR mRNA and protein in the hypothalamus and hippocampus were relatively stronger and optic value increased. The MOR mRNA and protein expressions in the hypothalamus and hippocampus relatively increased with statistical difference (P<0.01, P<0.05). Compared with the model group, the bands of products of MOR mRNA and protein in the parietal cortex and the frontal cortex were relatively enhanced, the MOR mRNA expression in the parietal cortex increased, the MOR protein expression in the parietal cortex and the frontal cortex increased in the Chinese herb treated group. The bands of products of MOR mRNA and protein in the hypothalamus and hippocampus were relatively weaker. The MOR mRNA and protein expressions in the hypothalamus and hippocampus relatively decreased. The MOR protein expression in the hippocampus decreased relatively with statistical difference (P<0.01, P<0.05).

CONCLUSIONSExpression of mu opioid receptor in brains of PMS Gan-qi invasion rats was regionally specific. Administration of JG showed corresponding regulatory effects.

Animals ; Brain ; metabolism ; Disease Models, Animal ; Drugs, Chinese Herbal ; pharmacology ; therapeutic use ; Female ; Premenstrual Syndrome ; drug therapy ; metabolism ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; genetics ; metabolism

OBJECTIVETo explore the role of µ-opioid receptors (MOR) in the central nucleus of the amygdala (CeA) in modulating sucrose solution intake in rats.

METHODSSprague-Dawley rats received intra-CeA injection of MOR agonist DAMGO or saline, and then underwent two bottle choice test between sucrose solution and distilled water. After intake of sucrose solution or distilled water, activated neurons in the CeA were labeled and identified with MOR/Fos-double labeling immunohistochemistry.

RESULTSCompared with saline injection, intra-CeA injection of DAMGO significantly increased sucrose solution intake in rats over a 3-h period. Sucrose solution intake induced significantly more c-Fos and MOR/Fos double-labeled neurons in the CeA than distilled water intake.

CONCLUSIONSThe CeA participates in modulation of sucrose intake in rats, and MOR may partly mediate this mechanism.

Amygdala ; metabolism ; Animals ; Male ; Neurons ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; metabolism ; Sucrose ; metabolism

A series of aralkyl-ketone-4-piperidol derivatives were synthesized and tested for their analgesic activities. All of the novel 30 compounds were prepared from 4-piperidone and alpha-halo-aralkyl-ketone through five steps, including Boc protection, nucleophilic addition in presence of CeCl3/NaI catalyst, deprotection, condensation and salification. Their structures were confirmed by 1H NMR and HRMS. Preliminary in vivo pharmacological trials showed that most of the synthesized compounds revealed analgesic effects. Among the tested compounds, 8, 13 and 22 exhibited potent analgesic activities in both mice writhing and mice hot plate model. The three compounds have low affinity for mu, delta, kappa receptors, which is a chance to find a better precursor of non-opioid analgesic for further optimization.
Analgesics, Non-Narcotic ; chemical synthesis ; chemistry ; pharmacology ; Animals ; Mice ; Molecular Structure ; Pain Measurement ; Pain Threshold ; drug effects ; Piperidones ; chemical synthesis ; chemistry ; pharmacology ; Receptors, Opioid, delta ; metabolism ; Receptors, Opioid, kappa ; metabolism ; Receptors, Opioid, mu ; metabolism ; Structure-Activity Relationship

OBJECTIVETo detect the distribution of beta-endorphin and mu-opioid receptors (MOR) in normal skin tissue and scar tissue from healthy volunteers and patients with hypertrophic scar.

METHODSNormal skin samples from 10 healthy individuals and 10 patients with hypertrophic scar, and scar samples from the same 10 patients were investigated. The beta-endorphin and MOR protein in the samples were detected by immunofluorescence (IF). The reverse transcription polymerase chain reaction (RT-PCR) was used to detect MOR mRNA.

RESULTSBeta-endorphin and MOR protein were expressed in all samples. There were no significant differences in the expression of beta-endorphin and MOR protein between normal skin from healthy volunteers and patients with hypertrophic scar (P > 0.05). The expression of beta-endorphin, MOR protein and mRNA in hyperplastic scar was significantly stronger than that in normal skin (P < 0.01).

CONCLUSIONSThe expression of beta-endorphin and MOR is different in normal skin and hypertrophic scar. This maybe the possible reason of scar paresthesia.

Case-Control Studies ; Cicatrix, Hypertrophic ; metabolism ; pathology ; Humans ; RNA, Messenger ; genetics ; Receptors, Opioid, mu ; metabolism ; Skin ; metabolism ; pathology ; beta-Endorphin ; metabolism

Compound SIPI5047 was synthesize by using piperazine as starting material in five reaction steps, and its central none-opioid analgesic activity was studied. Its analgesic activity, pharmacological mechanism, action type and drug dependence were well studied in vivo and in vitro. The results show that SIPI5047 has potent analgesic activities in vivo, which is quite similar to morphine and also much more powerful than paracetamol. SIPI5047 has no efficacy to reduce fever or inflammation, but has an obvious action on central nervous system. SIPI5057 has no apparent affinity with the mu-receptor and it is an antagonist that acts on the polyamine site of the NMDA receptor. SIPI5057 appears no drug dependence. SIPI5047 is a novel central none-opioid analgesic agent and more worthy of further research as a new drug candidate.
Analgesics ; chemical synthesis ; pharmacology ; toxicity ; Animals ; Female ; Male ; Mice ; Motor Activity ; drug effects ; Pain Measurement ; methods ; Piperazines ; chemical synthesis ; pharmacology ; toxicity ; Random Allocation ; Rats ; Rats, Sprague-Dawley ; Receptors, N-Methyl-D-Aspartate ; antagonists & inhibitors ; Receptors, Opioid, mu ; metabolism ; Substance-Related Disorders ; etiology

OBJECTIVETo observe the expression of beta-endorphin and micro-opioid receptor (MOR) during wound healing process in rat with deep partial-thickness scald.

METHODSThirty-six Wistar rats were randomly divided into control( n = 6, without treatment) , and scald ( n = 30, with 5% TBSA deep-partial thickness scald) groups. Skin specimens from wound were harvested immediately after scald and on 3, 7, 14, 21 post-scald days( PSD) for the determination of 1-endorphin and MOR expression with immunofluorescent staining.

RESULTSbeta-endorphin and MOR were mainly distributed in nerve terminal at the border of dermis and epidermis , keratinocyte in some epidermis , in the fibroblast in dermis , with a weak expression The expression of beta-endorphin peaked in whole layer of skin on 3 PSD( 196 +/-16, P <0. 01) ,while that of MOR was concentrated in keratinocytes in the basal layer and the basement membrane. The expression of MOR was strengthened on 7 PSD with disarrangement of collagen , and it peaked on 14 PSD (306 +/- 23, P < 0.01) with epithelization in some wounds. There was still strong expression of beta-endorphin on 7 and 14 PSD. Complete epithelization was observed in scald group on 21 PSD, with nerve terminal approaching the boundary between the dermis and epidermis, and collagen began to arrange in good order. The expression of P-endorphin in scald group (31 +/-24)was similar to that in control group(30 +/- 18) on 21 PSD, but the expression of MOR (56 +/- 16) was still higher than that in control group (28 +/- 15 ).

CONCLUSIONThe expression of MOR and P-endorphin exhibits chronobiological nature during the process of wound healing,

Animals ; Burns ; metabolism ; Disease Models, Animal ; Male ; Random Allocation ; Rats ; Rats, Wistar ; Receptors, Opioid, mu ; metabolism ; Wound Healing ; beta-Endorphin ; metabolism