Addicted Rats Research Articles

Addiction-related brain networks identification via Graph Diffusion Reconstruction Network

Functional magnetic resonance imaging (fMRI) provides insights into complex patterns of brain functional changes, making it a valuable tool for exploring addiction-related brain connectivity. However, effectively extracting addiction-related brain connectivity from fMRI data remains challenging due to the intricate and non-linear nature of brain connections. Therefore, this paper proposed the Graph Diffusion Reconstruction Network (GDRN), a novel framework designed to capture addiction-related brain connectivity from fMRI data acquired from addicted rats. The proposed GDRN incorporates a diffusion reconstruction module that effectively maintains the unity of data distribution by reconstructing the training samples, thereby enhancing the model’s ability to reconstruct nicotine addiction-related brain networks. Experimental evaluations conducted on a nicotine addiction rat dataset demonstrate that the proposed GDRN effectively explores nicotine addiction-related brain connectivity. The findings suggest that the GDRN holds promise for uncovering and understanding the complex neural mechanisms underlying addiction using fMRI data.

Bone marrow mesenchymal stem cells improve cognitive impairments induced by methamphetamine in rats and reduce relapse.

Introduction: Chronic exposure to methamphetamine (Meth) results in permanent central nervous system damage and learning and memory dysfunction. This study aimed at investigating the therapeutic effects of bone marrow mesenchymal stem cells (BMMSCs) on cognitive impairments in Meth addicted rats and comparing intravenous (IV) delivery with intranasal (IN) delivery of BMMSCs. Methods: Adult Wistar rats were randomly divided into 6 groups; Control; Meth-addicted; IV-BMMSC (Meth administered and received IV BMMSCs); IN-BMMSC (Meth administered and received IN BMMSCs); IV-PBS (Meth administered and received IV Phosphate-buffered saline (PBS); IN-PBS (Meth administered and received IN PBS). BMMSCs were isolated, expanded in vitro, immunophenotyped, labeled, and administered to BMMSCs-treated groups (2 × 106 cells). The therapeutic effect of BMMSCs was measured using Morris water maze and Shuttle Box. Moreover, relapse-reduction was evaluated by conditioning place preference after 2 weeks following BMMSCs administration. The expression of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) in rat hippocampus was assessed using immunohistochemistry method. Results: Administration of BMMSCs caused a significant improvement in the learning and memory functions of Meth-addicted rats and reduced the relapse (P<0.01). In behavioral tests, comparison of IV and IN BMMSC-treated groups did not show any significant difference. Administration of BMMSCs improved the protein level of BDNF and GDNF in the hippocampus, as well as causing behavioral improvement (P<0.001). Conclusion: BMMSC administration might be a helpful and feasible method to treat Meth-induced brain injuries in rats and to reduce relapse. BMMSCs were significantly higher in IV-treated group compared to the IN route. Moreover, the expression of BDNF and GDNF was higher in IN-treated rats compared with IV treated group.

Effects of valsartan on morphine tolerance and dependence in rats.

Background and purpose:Opiates are traditionally used for the treatment of pain. Chronic consumption of opiates such as morphine (MOR) induces tolerance and dependence. This study aimed to investigate the effects of valsartan (VAL), as an angiotensin II receptor blocker, on the induction and expression of MOR analgesic tolerance and physical dependence in rats.Experimental approach:MOR 10 mg/kg was injected s.c. twice a day for 7 days to induce tolerance and dependence. For evaluating the effect of VAL on the induction of MOR analgesic tolerance and physical dependence, 20 mg/kg VAL was administered orally (once a day) during the 7 days of the examination period. The tail-flick test was performed every day. On day 7, 5 mg/kg naloxone () was injected s.c. into the morphine-dependent rats and the rats were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake. For evaluating the effect of VAL on the expression of MOR-analgesic tolerance and physical dependence, 45 min before the last MOR injection, VAL was administered only on day 7. The tail-flick test was performed and naloxone was injected into the addicted rats and they were monitored for 30 min for the frequency of withdrawal signs such as jumping, diarrhea, defecation, head tremor, rearing, scratching, sniffing, teeth chattering, and wet-dog shake.Findings/Results:Our results revealed that the co-administration of VAL with MOR for 7 consecutive days reduced the induction of MOR tolerance. Moreover, VAL administration for 7 days along with MOR reduced the frequency of diarrhea and defecation in naloxone-injected animals.Conclusion and implications:According to the results presented in this study, chronic administration of VAL prevented the induction of MOR-analgesic tolerance and dependence in rats.

Drug-Seeking Behavior Is Significantly Attenuated in Nutritionally Supplemented Cocaine Withdrawn Sprague-Dawley Rats

Aim: The effect of patented nutritional supplementation on drug-seeking behavior in cocaine addicted rats during acute drug withdrawal was investigated using a biased Conditioned Place Preference (CPP) paradigm. Method: Twenty-four (24) male Sprague-Dawley rats with pre-conditioned preference for the black chamber of the CPP box were randomly divided into Cocaine (COC) or Saline (SAL) treated groups. Rats (n = 12) treated with cocaine hydrochloride 20 mg/kg/ml, i.p. (COC group) were confined individually to the white chamber on days 1, 3, 5 and 7. On alternate days, they were given 1 ml saline vehicle, i.p. and confined to the black chamber. Control rats (SAL group, n = 12) received only vehicle on all 8 days and were confined on alternate days to the white or black chamber. Positive place preference was confirmed for COC rats, which subsequently received 6 increasing daily doses of cocaine. CPP performances of both COC and SAL rats were recorded following an acute 3-day withdrawal period. All animals were then randomly assigned to rats fed either chow reconstituted with the nutritional supplement (COC-S and SAL-S) or standard rat chow (COC-N and SAL-N) for 8 weeks, followed by final CPP performances. Results: Following supplementation, COC-S rats made significantly less entries and time spent in the white chamber (p Conclusion: Drug-seeking behavior that persisted during cocaine withdrawal was significantly diminished in the nutritionally supplemented.

Identification of the status of individual drug-administration behavior in heroin-withdrawal rats based on FrA EEG

Objective: To identify the compulsive drug-seeking behavior of the individual in the heroin-addicted rat, a novel analysis method of telemetering electroencephalogram (EEG) in the frontal association cortex (FrA) induced by heroin-dependent position preference in rats. Methods: Thirty clean-grade Wistar rats after implantation of prefrontal cortex electrodes, were randomly divided into the surgical control group (n=10) and heroin-inducing group (n=20). The heroin-induced group was subcutaneously injected with heroin 0.5 mg/(kg.d), and then increased daily by 0.25 mg/kg for seven days. The control group was injected with the same amount of normal saline at the same time. Using the CPP video system combined with electroencephalogram (EEG) wireless telemetry technology, EEG signals in FrA areas of the addicted rats were recorded simultaneously in four behaviors: white-black shuttle, black-white shuttle, black-chamber stay and white-chamber stay. The areas with EMG and other noisy signals in the original EEG were identified, and wavelet decomposition and amplitude threshold denoising pre-processing were used. The sample entropy values of EEG data and wavelet coefficients corresponding to 4 rhythm frequencies under different behavioral states standard deviation were extracted, and support vector machine algorithm (SVM) was used to achieve real-time identification of different behavioral states of heroin-addicted rats. Results: SVM real-time classification recognition rate of 20 heroin abstinence rats, which are staying in black or white chamber of video box, shuttling between black-white chambers or between white - black chambers, was about 80%. Among them, the real-time recognition rate of black-white shuttle, which is closely related to drug-seeking behavior, reached 83.88%. Conclusion: In this paper, the real-time identification method of heroin-induced obsessive-compulsive drug-seeking behavior in rats can be used as an effective method to detect the initiation and occurrence of heroin-seeking drug-seeking behavior in rats. It can be used for the clinical observation of heroin-dependent patients and the prevention of drug-seeking behavior.

Nociceptin attenuates the escalation of oxycodone self-administration by normalizing CeA–GABA transmission in highly addicted rats

Approximately 25% of patients who are prescribed opioids for chronic pain misuse them, and 5 to 10% develop an opioid use disorder. Although the neurobiological target of opioids is well known, the molecular mechanisms that are responsible for the development of addiction-like behaviors in some but not all individuals are poorly known. To address this issue, we used a unique outbred rat population (heterogeneous stock) that better models the behavioral and genetic diversity that is found in humans. We characterized individual differences in addiction-like behaviors using an addiction index that incorporates the key criteria of opioid use disorder: escalated intake, highly motivated responding, and hyperalgesia. Using in vitro electrophysiological recordings in the central nucleus of the amygdala (CeA), we found that rats with high addiction-like behaviors (HA) exhibited a significant increase in γ-aminobutyric acid (GABA) transmission compared with rats with low addiction-like behaviors (LA) and naive rats. The superfusion of CeA slices with nociceptin/orphanin FQ peptide (N/OFQ; 500 nM), an endogenous opioid-like peptide, normalized GABA transmission in HA rats. Intra-CeA levels of N/OFQ were lower in HA rats than in LA rats. Intra-CeA infusions of N/OFQ (1 μg per site) reversed the escalation of oxycodone self-administration in HA rats but not in LA rats. These results demonstrate that the downregulation of N/OFQ levels in the CeA may be responsible for hyper-GABAergic tone in the CeA that is observed in individuals who develop addiction-like behaviors. Based on these results, we hypothesize that small molecules that target the N/OFQ system might be useful for the treatment of opioid use disorder.

Electrical stimulation mPFC affects morphine addiction by changing glutamate concentration in the ventral tegmental area.

Morphine addiction is known as a serious social problem. Medial prefrontal cortex (mPFC) and ventral tegmental area (VTA) are two important sites of the brain that contribute to this type of addiction, and a complicated relation exists in between. In addition, neurotransmitters like glutamate and γ--Amino Butyric Acid (GABA) play an important role in the formation of these relations. Thus, the present study was undertaken to investigate these relations by evaluating the level of associated changes in the indicated neurotransmitters in the VTA, using HPLC method. This was performed after electrical stimulation and inducing lesion of mPFC and through microinjections of N-Methyl-D-Aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonists, respectively AP5 and CNQX, into the VTA of addicted rats. Our results showed that intra-peritoneal (i.p.) administration of morphine in 9days in the morphine group, and also electrical stimulation (100μA) of mPFC, receiving (i.p.) morphine, caused an increase in the glutamate release in the VTA, compared to the control group, but the increase of glutamate levels in the VTA in the morphine-stimulation group was not significant, compared to the morphine group. Moreover, GABA release into this area was decreasing in morphine and morphine- stimulation groups, compared to the control group. Our findings also showed that electrical lesion (0.4mA) of mPFC, and also microinjection of glutamate antagonists into the VTA, receiving (i.p.) morphine in rats, caused a decrease of glutamate in the VTA. Therefore, it could be concluded that the relation between mPFC and VTA is highly effective in the formation of reward system.

Drinking Levels and Profiles of Alcohol Addicted Rats Predict Response to Nalmefene.

Background: Pharmacotherapeutic options supporting the treatment of alcohol dependence are recommended and available but underutilized, partly due to questions about efficacy. Nalmefene, a μ-opioid receptor antagonist and partial kappa receptor agonist, is recommended for reduction of alcohol consumption, but evidence about its effectiveness has been equivocal; identifying factors which predict response will help optimize treatment.Methods: The alcohol deprivation effect paradigm is a tightly controlled procedure comprising repeated deprivation and reintroduction phases, leading to increased preference for alcohol; reintroduction approximates relapse. Using a digital drinkometer system measuring high-resolution drinking behavior, we examined the effects of nalmefene on relapse drinking behavior in alcohol addicted rats. We also tested whether drinking behavior in the relapse phase prior to nalmefene administration predicted treatment response. We further examined whether longitudinal drinking behavior and locomotor activity predicted treatment response.Results: Our results showed that nalmefene (0.3 mg/kg) reduced relapse-like consumption significantly (∼20%) compared to vehicle on the first 2 days of alcohol reintroduction. Examining the first 6 h of a preceded treatment-free relapse episode revealed drinking patterns clustering the rats into responders (reduction of >40%, n = 17) and non-responders (reduction of <40%, n = 7) to subsequent nalmefene treatment. During the first 6 h of the preceding relapse phase, responders consumed more alcohol than non-responders; the amount of alcohol consumed during each drinking approach was larger but frequency of drinking did not differ. Longitudinal drinking behavior and locomotor activity did not significantly predict response.Conclusion: Our results suggest that nalmefene reduces alcohol intake during a relapse-like situation but effectiveness can differ greatly at the individual level. However, who responds may be informed by examining drinking profiles and rats that show high drinking levels prior to treatment are more likely to respond to nalmefene.

Berberine hydrochloride attenuates voluntary methamphetamine consumption and anxiety-like behaviors via modulation of oxytocin receptors in methamphetamine addicted rats

ObjectiveMethamphetamine (METH) addiction is recognized as one of the major public health concerns, with no approved pharmacological agents for treatment. Berberine hydrochloride, an isoquinoline alkaloid in plants, induces antipsychotic and anxiolytic effects. Hence, we hypothesized that berberine may modulate the METH-induced rewarding effects. Materials and methodsIn this study, three groups of rat including control (N = 10), METH + vehicle (N = 10), and METH + berberine (N = 10) were kept in separate cages one day before expriments. METH (20 mg/L) was dissolved in tap water inside a bottle, while there was only tap water in the control bottle. Two groups received free METH solutions for two weeks (up to 12 mg/kg). Afterwards, they were abstianced for three weeks. Only one group received 100 mg/kg/day of berberine. After three weeks, locomotor activity and anxiety (elevated plus maze test) were evaluated, then the two-bottles choice model was used for one week to evaluate drug preferences. Finally, the brain of rats was removed for evaluation of oxytocin receptor expression via immunofluorescence staining method. ResultsThe results showed that METH preference was lower in the berberine + METH group during drug intake compared to the METH group (P < .05). During withdrawal, berberine reduced anxiety-like behaviors (P < .05) and decreased locomotor activity versus the METH group (P < .001). Also, berberine increased numbers of oxytocin receptors in comparison with the METH group (P < .01). ConclusionConsidering the modulation of oxytocin receptors, berberine may be considered as a potential therapeutic agent for METH addiction.

Theta–gamma coupling in the prelimbic area is associated with heroin addiction

The medial prefrontal cortex (mPFC) is implicated in the regulation of drug-seeking behavior, but the specific contributions of the mPFC prelimbic (PL) subdivision and the precise mechanisms underlying heroin abuse remain largely unclear. In the present study, we examined changes in the rhythmic ensemble activity of PL neurons after induction of heroin addiction in rats. Rats were injected daily with saline (control group) or heroin (addiction group) in the light chamber of a light−dark shuttle box, and a video tracking system was used to measure conditioned place preference (CPP) as a sign of addiction. A wireless telemetry system was used to record local field potentials (LFPs) from the PL area during expression of CPP. Before treatment, there was no difference in CPP between groups (P > 0.05). However, rats in the experimental group exhibited significant CPP (P < 0.05) in the light chamber after heroin treatment compared to before treatment and compared to control rats. During CPP, addicted rats demonstrated substantial alterations in relative θ and γ frequency band power (Ps < 0.05); moreover, the θ wave alteration was strongly coupled to γ waves in heat map analyses (P < 0.05). Collectively, these findings implicate heroin-induced alterations in PL area neural activity and θ−γ coupling in heroin addiction.

A dopamine D1 receptor agonist improved learning and memory in morphine-treated rats

ABSTRACTObjective: The objective of this article is to study the role of the dopamine (DA) D1 receptor in the midbrain periaqueductal grey (PAG) on learning and memory in morphine-addicted rats.Methods: DA D1 receptor agonist SKF81297 and D1 receptor antagonist SCH SCH23390 were administrated into the PAG, respectively, and the learning and memory behavioral changes of morphine addicted rats were detected by water maze. Western blot and immunohistochemistry were used to detect glutamate decarboxylase 67 (GAD67) and tyrosine receptor kinase B (TrkB) in PAG.Results: D1 receptor agonist shortened the latency to platform and increased the number of platform crossings, indicating improved learning and memory ability of morphine addict rat. D1 receptor agonist increased GAD67 expression and decreased TrkB in PAG.Conclusion: (1) The PAG is involved in the learning and memory changes of the addicted rats; (2) the activation of DA D1 receptor will increase the GAD67, reduce the damage to peripheral neurons, and improve the learning and memory of the addicted rats; and (3) D1 receptor agonists further reduced TrkB expression in morphine-addicted rats, whereas TrkB levels deviated from changes in rat behavior.

In vivo electrochemical assessment of dopamine release during conditioned withdrawal in heroin dependent rats

The centers for disease control and prevention reports that heroin abuse has doubled for Americans aged 18–25. Drugs of abuse, such as heroin, are commonly thought to increase the concentration of dopamine (DA) in the nucleus accumbens core (NAcc), although their effects on phasic DA release events remains to be fully characterized. In contrast, when an addicted subject is withdrawn from a substance such as heroin, there is a clear suppression of phasic DA activity in the NAcc. Heroin withdrawal presents characteristic symptoms, most predominately increased craving for the drug, which contributes to further abuse. While withdrawal symptoms have been shown to be conditioned to previously neutral stimuli through classical conditioning, there is a lack of electrochemical evidence of conditioned withdrawal and its effects on non‐drug related stimuli. Here, we sought to explore how conditioned withdrawal in heroin addicted rats affects DA. We provided rats 23 hour access to IV heroin over 28 days. The 28 days are split into four blocks of increasing doses ranging from 0.06 mg/kg to 6 mg/kg to more accurately simulate the progression of heroin addiction. During the 28 day history, circadian changes in heroin, food, and water intake were altered and overall consumption of heroin increased. We then, investigated how conditioned withdrawal affects cue‐evoked dopamine release in the NAcc using fast scan cyclic voltammetry (FSCV) during conditioned suppression of food maintained responding. Here, animals were first trained to respond for food under an FR1 schedule for 3 consecutive days where food availability was predicted by a cue‐light placed above the lever. This was followed by 3 consecutive days of conditioned withdrawal training where a tone was conditioned to naloxone‐precipitated withdrawal. On test day, animals responded for food under normal conditions, but the withdrawal associated tone was presented concurrently with cue‐light onset during 50% of trials. By simultaneously presenting the withdrawal paired tone with the food predictive cue light we observed a substantial suppression of DA concentration at the cue light relative to non‐paired trials. These data demonstrated that conditioned suppression of food maintained responding induced by conditioned heroin withdrawal is accompanied by a transient suppression in dopamine concentrationSupport or Funding InformationFunding for the project was provided by NSF grant IOS‐1557755, NIH grant R03DA038734, Boettcher Young Investigator Award and NARSAD Young Investigator Award to EBO and an institutional UROP to KJP.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Translational FDG-PET studies in alcohol and cocaine addicted rats

Translational FDG-PET studies in alcohol and cocaine addicted rats

Mechanical Stimulation of the HT7 Acupuncture Point to Reduce Ethanol Self-Administration in Rats.

Background Alcoholism, which is a disabling addiction disorder, is a major public health problem worldwide. The present study was designed to determine whether the application of acupuncture at the Shenmen (HT7) point suppresses voluntary alcohol consumption in addicted rats and whether this suppressive effect is potentiated by the administration of naltrexone. Methods Rats were initially trained to self-administer a sucrose solution by operating a lever. A mechanical acupuncture instrument (MAI) for objective mechanical stimulation was used on rats whose baseline response had been determined. In addition, the effect of HT7 acupuncture on beta-endorphin concentration and ethanol intake via naltrexone were investigated in different groups. Results We found that ethanol intake and beta-endorphin level in rats being treated with the MAI at the HT7 point reduced significantly. The treatment of naltrexone at high doses reduced the ethanol intake and low-dose injection of naltrexone in conjunction with the MAI also suppressed ethanol intake. Conclusions The results of the current study indicate that using the MAI at the HT7 point effectively reduces ethanol consumption in rats. Furthermore, the coadministration of the MAI and a low dose of naltrexone can produce some more potent reducing effect of ethanol intake than can acupuncture alone.

Evaluation of CART peptide level in rat plasma and CSF: Possible role as a biomarker in opioid addiction

It has been shown previously that cocaine- and amphetamine-regulated transcript (CART) peptide has a modulatory role and homeostatic regulatory effect in motivation to and reward of the drugs of abuse specially psychostimulants. Recent data also showed that in addition to psychostimulants, CART is critically involved in the different stages of opioid addiction. Here we have evaluated the fluctuations in the level of CART peptide in plasma and CSF in different phases of opioid addiction to find out whether CART can serve as a suitable marker in opioid addiction studies. Male rats were randomly distributed in groups of control, acute low-dose (10mg/kg) morphine, acute high-dose morphine (80mg/kg), chronic escalating doses of morphine, withdrawal syndrome precipitated by administration of naloxone (1mg/kg), and abstinent after long-term drug-free maintenance of addicted animals. The level of CART peptide in CSF and plasma samples was measured by enzyme immunoassay. CART peptide concentration in the CSF and plasma was significantly elevated in acute high-dose morphine and withdrawal state animals and down-regulated in addicted rats. In abstinent group, CART peptide level was up-regulated in plasma but not in CSF samples. As the observed results are in agreement with data regarding the CART mRNA and protein expression in the brain reward pathway in opioid addiction phases, it may be suggested that evaluation of CART peptide level in CSF or plasma could be a suitable marker which reflects the rises and falls of the peptide concentration in brain in the development of opioid addiction.

Genome-wide DNA hydroxymethylation identifies potassium channels in the nucleus accumbens as discriminators of methamphetamine addiction and abstinence

Epigenetic consequences of exposure to psychostimulants are substantial but the relationship of these changes to compulsive drug taking and abstinence is not clear. Here, we used a paradigm that helped to segregate rats that reduce or stop their methamphetamine (METH) intake (nonaddicted) from those that continue to take the drug compulsively (addicted) in the presence of footshocks. We used that model to investigate potential alterations in global DNA hydroxymethylation in the nucleus accumbens (NAc) because neuroplastic changes in the NAc may participate in the development and maintenance of drug-taking behaviors. We found that METH-addicted rats did indeed show differential DNA hydroxymethylation in comparison with both control and nonaddicted rats. Nonaddicted rats also showed differences from control rats. Differential DNA hydroxymethylation observed in addicted rats occurred mostly at intergenic sites located on long and short interspersed elements. Interestingly, differentially hydroxymethylated regions in genes encoding voltage (Kv1.1, Kv1.2, Kvb1 and Kv2.2)- and calcium (Kcnma1, Kcnn1 and Kcnn2)-gated potassium channels observed in the NAc of nonaddicted rats were accompanied by increased mRNA levels of these potassium channels when compared with mRNA expression in METH-addicted rats. These observations indicate that changes in differentially hydroxymethylated regions and increased expression of specific potassium channels in the NAc may promote abstinence from drug-taking behaviors. Thus, activation of specific subclasses of voltage- and/or calcium-gated potassium channels may provide an important approach to the beneficial treatment for METH addiction.

Electrical stimulation of prelymbic with different currents intensities on morphine induced spatial memory deficit in rats.

Background:The medial prefrontal cortex (mPFC) is a part of brain reward system involved in cognitive functions such as learning and memory. Previous studies showed that electrical stimulation of prelymbic produced different effects on morphine-induced condition place preference. In this study, we investigated the electrical stimulation with different current intensities on spatial memory in rats.Materials and Methods:In this study, male Wister rats weighing approximately 200–300 g were used. The effect of prelymbic electrical stimulation with 25 and 150 μA currents intensities in healthy and addicted rats on spatial memory was studied. Spatial memory was investigated using the Morris water maze test in addicted rats after 9 days of electrical stimulation.Results:Our findings have shown that morphine reduces the memory and learning, whereas the present results indicated that electrical stimulation of prelymbic area with current intensity of the 25 μA shortened the time and distance to reach to platform that indicated improvement in spatial memory on addicted rats. Whereas the electrical stimulation of prelymbic area with the current intensity of 150 μA has special weakening effects on spatial memory and prolongs the time and distance to reach the platform.Conclusions:The electrical stimulations of prelymbic with 25 μA current intensity improved the spatial memory in addicted rats while with 150 μA current intensity weakened spatial memory in rats. It is possible that increase in the release of some neurotransmitters reverses the effect of morphine on spatial memory.

Effect of acetylcholine receptors on the pain-related electrical activities in the hippocampal CA3 region of morphine-addicted rats.

To determine the effect of acetylcholine (ACh), pilocarpine, and atropine on pain evoked responses of pain excited neurons (PEN) and pain inhibited neurons (PIN) in hippocampal CA3 region of morphine addicted rats. Female Wistar rats, weighing between 230-260 g were used in this study. Morphine addicted rats were generated by subcutaneous injection of increasing concentrations of morphine hydrochloride for six days. Trains of electrical impulses applied to the sciatic nerve were used as noxious stimulation and the evoked electrical activities of PEN or PIN in hippocampal CA3 area were recorded using extracellular electrophysiological recording techniques in hippocampal slices. The effect of acetylcholine receptor stimulation by ACh, the muscarinic agonist pilocarpine, and the muscarinic antagonist atropine on the pain evoked responses of pain related electrical activities was analyzed in hippocampal CA3 area of morphine addicted rats. Intra-CA3 microinjection of ACh (2 μg/1 μl) or pilocarpine (2 μg/1 μl) decreased the discharge frequency and prolonged the firing latency of PEN, but increased the discharge frequency and shortened the firing inhibitory duration (ID) of PIN. The intra-CA3 administration of atropine (0.5 μg/1 μl) produced opposite effect. The peak activity of cholinergic modulators was 2 to 4 min later in morphine addicted rats compared to peak activity previously observed in normal rats. ACh dependent modulation of noxious stimulation exists in hippocampal CA3 area of morphine addicted rats. Morphine treatment may shift the sensitivity of pain related neurons towards a delayed response to muscarinergic neurotransmission in hippocampal CA3 region.

The effect of medial prefrontal cortex electrical stimulation on passive avoidance memory in healthy and addict rats.

Background:The medial prefrontal cortex (mPFC) is a part of brain reward system involved in cognitive functions such as learning and memory. The mPFC receives strong dopaminergic innervations from ventral tegmental area (VTA) that comprises a portion of the mesolimbic dopaminergic system (MLDS), and sends glutamatergic projections to both the VTA and nucleus accumbens (NAc).Materials and Methods:In this study, male Wister rats weighing 250-350 g were used. The effect of medial prefrontal cortex (mPFC) electrical stimulation with different current intensities (25, 50,100, and 150 μA) in healthy and addicted rats on passive avoidance memory was studied here.Results:This study showed that 25 and 150 μA had no effect on improving avoidance memory in rats. Current intensities of 50 and 100 μA differ significantly with 25 and 150 μA. The PL of mPFC contributes to memory processing.Conclusions:The electrical stimulations of prelimbic with 50 and 100 μA current intensities were improved avoidance memory in addicted rats while learning impairment is caused in healthy rats while the electrical stimulation with these used current intensities.

Protective effects of tetrandrine on brain cells in phenobarbital-dependent and -withdrawn rats.

The aim of this study was to investigate the effects of tetrandrine (Tet) on the brain cells of phenobarbital‑dependant and ‑withdrawn rats, and to explore the underlying mechanisms. A total of 100 rats were randomly divided into five groups: The control group, the phenobarbital‑dependent model group, and Tet‑treated groups of low‑, mid‑ and high‑dosages. Following drug withdrawl, the morphological changes of the frontal lobe cells were examined by hematoxylin and eosin (H&E) staining. Immunohistochemical staining was applied to detect the expression of apoptosis‑related proteins Bcl‑2 and Bax. Reverse transcription‑polymerase chain reaction (RT‑PCR) and western blotting methods were applied to detect the mRNA and protein expression levels of Bcl‑2 and Bax, respectively, in the frontal lobe. The results indicated that Tet effectively reduced the withdrawal symptoms, particularly the weight loss, in phenobarbital‑dependent and ‑withdrawn rats. H&E staining revealed that Tet significantly restored the histopathological changes in the addicted rats in a dose‑dependent manner. The immunohistochemical, RT‑PCR, and western blot analyses indicated that Tet treatment significantly increased the Bcl‑2+ brain cells and the mRNA and protein expression levels of Bcl‑2, and decreased the Bax+ cells and the mRNA and protein expression levels of Bax, as well as elevated the ratio of Bcl‑2/Bax, in phenobarbital‑dependent and ‑withdrawn rats. Tet may inhibit apoptosis in these addicted rats, in a dose‑dependent manner. Tet alleviates the phenobarbital withdrawal symptoms and protects the brain cells against apoptosis, which may be a result of the regulation of the mRNA and protein expression levels of Bcl‑2 and Bax.