Effect of Transient Inactivation of Ventral Tegmental Area on the Expression and Acquisition of Nicotine-Induced Conditioned Place Preference in Rats

Background:

Nicotine can activate dopaminergic neurons within the ventral tegmental area (VTA). However, there is no evidence about complete inhibition of VTA on nicotine reinforcement.

Methods:

in the present study, we used conditioned-place preference (CPP) method to study the effect of transient inhibition of left and/or right side of the VTA by lidocaine on nicotine reward properties. Male Wistar rats seven days after recovery from surgery and cannulation were conditioned to nicotine (1.5 mg/kg) in an unbiased designed CPP apparatus. Five min before each nicotine injection in conditioning phase, lidocaine (2%) was administered either uni- or bi-laterally into the VTA (0.5µl/rat).

Results:

results revealed that lidocaine administration into the left but not right side of the VTA reduced nicotine CPP significantly. The reduction was potentiated when lidocaine injected in to both sides of the VTA. In addition, the number of compartment crossing was reduced when lidocaine injected in both side of VTA as well as left side. On the other hand, rearing was reduced when lidocaine injected to the right but not left side of VTA. At last, sniffing was reduced only in the group in which received lidocaine in both side of VTA. Sniffing and rearing increased in the group in which received lidocaine in right side.

Conclusion:

It is concluded that the right and left side of VTA play different role in nicotine-induced activity and reward.

Common behaviors alterations after extremely low-frequency electromagnetic field exposure in rat animal model

Naturally, the presence of electromagnetic waves in our living environment affects all components of organisms, particularly humans and animals, as the large part of their body consists of water. In the present study, we tried to investigate the relation between exposure to the extremely low-frequency electromagnetic field (ELF-EMF) and common behaviors such as body weight, food and water intake, anorexia (poor appetite), plasma glucose concentration, movement, rearing and sniffing in rats. For this purpose, rats were exposed to 40  Hz ELF-EMF once a day for 21 days, then at days 1, 3, 7, 14 and 21 after exposure, any changes in the above-mentioned items were assessed in the exposed rats and compared to the non-exposed group as control. Body weight of irradiated rats significantly increased only a week after exposure and decreased after that. No significant change was observed in food and water intake of irradiated rats compared to the control, and the anorexia parameter in the group exposed to ELF-EMF was significantly decreased at one and two weeks after irradiation. A week after exposure, the level of glucose was significantly increased but at other days these changes were not significant. Movements, rearing and sniffing of rats at day 1 after exposure were significantly decreased and other days these changes did not follow any particular pattern. However, the result of this study demonstrated that exposure to ELF-EMF can alter the normal condition of animals and may represent a harmful impact on behavior.

The Effects of Fifa 2015 Computer Games on Changes in Cognitive, Hormonal and Brain Waves Functions of Young Men Volunteers

INTRODUCTION

Computer games have attracted remarkable attentions in general publics with different cultures and their effects are subject of research by cognitive neuroscientists. In the present study, possible effects of the game Fifa 2015 on cognitive performance, hormonal levels, and electroencephalographic (EEG) signals were evaluated in young male volunteers.

METHODS

Thirty two subjects aged 20 years on average participated mutually in playing computer game Fifa 2015. Identification information and general knowledge about the game were collected. Saliva samples from the contestants were obtained before and after the competition. Perceptive and cognitive performance including the general cognitive health, response delay, attention maintenance, and mental fatigue were measured using PASAT test. EEG were recorded during the play using EEG device and analyzed later using QEEG. Simultaneously, the players' behavior were recorded using a video camera. Saliva cortisol levels were assessed by ELISA kit. Data were analyzed by SPSS program.

RESULTS

The impact of playing computer games on cortisol concentration of saliva before and after the game showed that the amount of saliva plasma after playing the game has dropped significantly. Also the impact of playing computer games on mental health, before and after the game indicated that the number of correct answers has not changed significantly. This indicates that sustained attention has increased in participants after the game in comparison with before that. Also it is shown that mental fatigue measured by PASAT test, did not changed significantly after the game in comparison to before that. The impact of game on changes in brain waves showed that the subjects in high activity state during playing the game had higher power of the EEG signals in most of the channels in lower frequency bands in compared to normal state.

DISCUSSION

The present study showed that computer games can positively affect the stress system and the perceptual-cognitive system. Even though this impact was not significant in most cases, the changes in cognitive and hormonal test and also in brain waves were visible. Hence, due to the importance of this matter, it is necessary to create control systems in selecting the types of games for playing.

Effects of electromagnetic radiation exposure on stress-related behaviors and stress hormones in male wistar rats

Studies have demonstrated that electromagnetic waves, as the one of the most important physical factors, may alter cognitive and non-cognitive behaviors, depending on the frequency and energy. Moreover, non-ionizing radiation of low energy waves e.g. very low frequency waves could alter this phenomenon via alterations in neurotransmitters and neurohormones. In this study, short, medium, and long-term exposure to the extremely low frequency electromagnetic field (ELF-EMF) (1 and 5 Hz radiation) on behavioral, hormonal, and metabolic changes in male Wistar rats (250 g) were studied. In addition, changes in plasma concentrations for two main stress hormones, noradrenaline and adrenocorticotropic hormone (ACTH) were evaluated. ELF-EMF exposure did not alter body weight, and food and water intake. Plasma glucose level was increased and decreased in the groups which exposed to the 5 and 1Hz wave, respectively. Plasma ACTH concentration increased in both using frequencies, whereas nor-adrenaline concentration showed overall reduction. At last, numbers of rearing, sniffing, locomotor activity was increased in group receiving 5 Hz wave over the time. In conclusions, these data showed that the effects of 1 and 5 Hz on the hormonal, metabolic and stress-like behaviors may be different. Moreover, the influence of waves on stress system is depending on time of exposure.

Nitric oxide in central amygdala potentiates expression of conditioned withdrawal induced by morphine

Objective:

The aim of this study was to evaluate if nitric oxide (NO) in the central amygdala (CeA) is involved in the expression of withdrawal aspects induced by morphine.

Materials and Methods:

Male Wistar rats (weighing 200-250 g) were bilaterally cannulated in the CeA and conditioned to morphine using an unbiased paradigm. Morphine (2.5-10 mg/kg) was subcutaneously injected once a day throughout the conditioning phase of the procedure. This phase also included 3-saline paired sessions. Naloxone (0.1-0.4 mg/kg, intraperitoneally [i.p.]), an antagonist of opioid receptors, was administered i.p. 10 min prior to testing of morphine-induced withdrawal features. The NO precursor, L-arginine (0.3-3 μg/rat) was intra-CeA injected prior to testing of naloxone response. To evaluate the involvement of NO system an inhibitor of NO synthase (NOS), N^G-nitro-L-arginine methyl ester (L-NAME) (0.3-3 μg/rat), was injected ahead of L-arginine. Control group received saline solely instead of drug. As a complementary study, the activation of NOS was studied by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d).

Results:

Morphine induced a significant increase in wet dog shaking and grooming behaviors compared with controls. Injection of naloxone pre-testing of morphine response significantly reversed the response to morphine. However, pre-microinjection of L-arginine intra-CeA recovered the response to morphine. Injection of L-NAME intra-CeA ahead of L-arginine though had no effect behaviorally, but, inhibited the NOS which has been evidenced by NADPH-d.

Conclusion:

The present study shows that NO in the CeA potentiates the expression of conditioned withdrawal induced by morphine paired with naloxone.

Reduction of metabolic signs of acute stress in male mice by Papaver rhoaes hydro-alcoholic extract

In the present study, effects of hydro-alcoholic extract of Papaver rhoeas L. (Papaveraceae) on the metabolic changes induced by electro foot shock stress in male NMRI mice (25-30 g) has been investigated. The mice were received electric foot shock (40 mV) for 100 sec. Plasma corticosterone levels, food and water intake and delay to eating (Anorexia) were assessed 20 min later. Different doses of the plant extract (15, 30 and 60 mg kg(-1)), or saline (10 mL kg(-1)) was injected to the animals intraperitoneally 30 min before the stress. The control groups received saline (10 mL kg(-1)) or the extract (15, 30 and 60 mg kg(-1)) and 30 min later were exposed to the apparatus but did not received stress. Our results indicated that stress can increase plasma corticosterone level significantly and the extract can exacerbate the stress effect. However, stress could reduce food and water intake and increase delay to eating times which were inhibited by the extract pretreatment. The results indicate that administration of the extract of Papaver rhoeas can reduce the side effects of stress but increases plasma corticosterone level which may be due to its effects on the adrenal gland.

New view on treatment of drug dependence

In the 1960s, discovery of pleasure system (defined as reward system) in the brain that may underlie drug reward and addiction encouraged many scientists to investigate the mechanisms by which drug abuse affects central nervous system function. In this regard, investigators developed several drugs targeting the brain reward system for drug dependence therapy. However, no positive results obtained in drug addiction treatment. It seems that more brain systems other than brain reward system must be considered in this regard.

Effects of Papaver rhoeas (L.) extract on formalin-induced pain and inflammation in mice

Stress amelioration can improve its metabolic as well as other side effects. In the present study, the effects of hydro-alcoholic extract of Papver rhoeas (L.) on formalin-induced pain and inflammation were investigated in male Swiss-Webster mice (20-25 g). Formalin injects in the plantar portion of mice hind paw and pain was studied for 60 min. The plant extract and other drugs were administered intraperitoneally 30 min before formalin. Experiments showed that administration of extract (25, 50 and 100 mg kg(-1)) could induced analgesia in a dose-response manner in both phases of formalin test. More over, the extract inhibits inflammation induced by formalin injection. Naloxone (4 mg kg(-1)), dextromethorphan (20 mg kg(-1)) and NG-nitro-L-arginine-methylester (L-NAME; 10 mg kg(-1)) reduced the extract analgesia in first but not late phase. Extract administration also increased plasma corticosterone level in dose-dependent manner. It could be concluded that Papaver rhoeas (L.) extract could inhibits acute phase of formalin test in mice by opioidergic, glutamatergic and nitricergic mechanisms. In addition, the extract can induce corticosterone plasma level which may be responsible for inhibition of inflammation and chronic phase of pain induced by formalin.

Identification of morphine accumulation in the rat embryo central nervous system: a c14-morphine administration study

BACKGROUND

Previous studies have shown that morphine consumption during pregnancy may cause delay or defect of embryo development or abnormal nervous system function in the human and animal models. In the present study, the highest density of morphine accumulation in the central nervous system of rat embryos was evaluated using C14-morphine.

METHODS

Female Wistar rats (W 170-200 g) used and were crossed with male rats and coupling time was recorded (Embryonic day 0-E0). Experimental groups received 0.05 mg/ml of C14-morphine in drinking water daily. On the 10(th) and 17(th) days of pregnancy, pregnant rats were anesthetized and the embryos with these uterus and placenta were surgically removed and were fixed in formalin 10% for 4 week. Then the embryos were processed, sectioned in 25 μm and 5 μm thicknesses, fixed on the glasses for further evaluations. The sectioned in 25, the glasses were fixed on the Blanc black and white film for 6 h. Then, the films were appeared and their negatives were prepared. The sectioned in five staining hematoxylin and eosin by light microscope and MOTIC software.

RESULTS

Our results indicated that the highest C14-morphine accumulation was observed in the vesicles and the ventricular choroid plexus (CP) of (E17) embryos, whereas, in the (E10) embryos. Highest concentration was observed in the brain vesicles and the ventricular CP. In addition, this study showed the surface area of lateral, 3(rd) and 4(th) ventricular CP in the experimental groups were increased in compared to control groups.

CONCLUSIONS

Our results indicated that effects of morphine on reduction of embryos brain development may be due to the highest accumulation of C14-morphine in the CP and brain vesicles.

Hydroalcoholic extract of Rosemary (Rosmarinus officinalis L.) and its constituent carnosol inhibit formalin-induced pain and inflammation in mice

The anti-inflammatory and anti-nociceptive properties of Rosmarinus officinalis L. (ROL) extract and its major constituent, carnosol in male NMRI mice (W:25-30 g) have been evaluated in the present study. Formalin (2%, 20 microL) was injected into the plantar portion of the hind paw and resulting pain and inflammation was studied for 60 min. The plant extract, carnosol and other drugs were administered intraperitoneally or subcutaneously 30 min before formalin injection. In a separate experiment, the effects of the extract and carnosol on plasma corticosterone levels and activity of the enzymes cyclooxygenase type 1 and 2 (COX1 and COX2) were investigated. Injection of different doses of ROL and carnosol reduced pain in the phase 2 of the formalin test, which was not inhibited by naloxone and/or memantine. In addition, pretreatment of the animals with ROL and/or carnosol reduces the formalin-induced inflammation. Furthermore, the extract and carnosol did not affect plasma corticosterone levels compared with the control group. Interestingly, both the extract and carnosol inhibited COX1 and COX2 activity. It could be concluded that ROL extract and carnosol suppressed pain and inflammation induced by formalin injection, which may be due to inhibition of COX1 and COX2 enzymes activity.

Evaluating the effects of oral morphine on embryonic development of cerebellum in wistar rats

In the present research, the effect of morphine consumption during pregnancy on the development of the embryo's spinal cord was studied in Wistar rat.

FEMALE WISTAR RATS (WT

250-300 g) were mated with males. The test group received morphine (0.01 mg/ml) in their drinking water. Pregnant rats were later killed with chloroform on the 12th, 13th and 14th days of pregnancy, and the embryos were taken out surgically. The embryos were fixed in formalin 10% for 2 weeks. Then, the weight of fixed embryos was calculated by a scale. In addition, several animals' sizes including fronto-posterior and lateral length were measured by a caliper. Tissue processing, sectioning and hematoxylin and eosin (H&E) staining were applied for the embryos. The sections were examined for spinal cord development by light microscope and MOTIC software. Significant decrease was observed in the fronto-posterior and lateral length and the weight of the embryos in the test groups. The thickness of the white matter layer decreased on the 12th, 13th and 14th embryonic days. The thickness of the spine's grey layer was also less than the control group, on the same days. Increase in the length of the ependimal duct observed as well. Number of grey substance cells decreased compared to the control group within the same days. Meanwhile, thickness of the germinal layer reduced in comparison to the control group on the mentioned days. In conclusion, morphine consumption during pregnancy causes defects in growth and completion of the spinal cord.

Experiences living with fatigue in Iranian veterans chemically injured by sulfur mustard gas: a phenomenological study

PURPOSE

Fatigue affects the quality of life. Evidence shows that the phenomenon of fatigue is experienced differently depending on the type of disease and its consequences. The aim of the study was to explicate the meanings of the experience of living with fatigue in chemically injured veterans.

METHODS

The hermeneutic phenomenology approach was used in this study, with an emphasis on Van Mennen's viewpoint and approach. According to Van Mennen, six overlapping dynamic activities are recommended to conduct a phenomenological study. During unstructured interviews, the participants were asked to describe their daily living experiences with fatigue. The participants were individuals who were chemically injured due to exposure to mustard gas. After examining every statement in the interview text, extractions of the meaning units, clustering, and themes were performed.

RESULTS

The data explication was based on the third to sixth stages of Van Mennen's approach. The experience living with fatigue was classified into four essential themes: fatigue as a chronic condition, as an unstable and affected situation, as a physical condition of the entire individual, and as a mental condition of the entire individual.

CONCLUSION

Due to unique social interactions and pathogenicity, victims of mustard gas experience fatigue differently than patients with other chronic diseases.

The effect of music on the level of cortisol, blood glucose and physiological variables in patients undergoing spinal anesthesia

Surgical procedures performed using spinal anesthetic techniques present a special challenge to anesthesiologists, because patients are awake and are exposed to multiple anxiety provoking visual and auditory stimuli. Therefore, this study was carried out to define the effect of music on the level of cortisol, blood glucose and physiological variables in patients under spinal anesthesia. In this semi-experimental research, 90 men aging from 18-48 years with ASA (acetylsalicylic acid) class I, who underwent urological and abdominal surgery, were investigated. Patients were divided randomly into three groups of thirty subjects. Music group (headphone with music), Silence group (headphone without music) and the control group (without interference). The level of cortisol and blood sugar was measured half an hour before and after the operation. Moreover, the physiological indicators in each of these three groups were monitored and recorded from ten minutes before getting spinal anesthesia to ten minutes after the operation. The level of blood cortisol didn't have any increase in the music group after operation compared to the time before that. However, in the groups of silence and control this level had risen (p< 0.05). The level of blood glucose in music group had declined and in the other two groups it had increased. Our data showed that listening to music during surgery under regional anesthesia has effects on cortisol levels and some of the physiological variables. Therefore the researcher offers to be used music therapy as a complementary method in patients on the reduce anxiety.

Transient inactivation of the nucleus accumbens reduces both the expression and acquisition of morphine-induced conditioned place preference in rats

In the present study, the effects of transient inhibition of the shell and core parts of the nucleus accumbens by lidocaine on the expression and acquisition of morphine-induced conditioned place preference in male Wistar rats were investigated. In addition, the number of bouts of sniffing, rearing, and compartment crossing was scored. Lidocaine hydrochloride was injected into different parts of the nucleus accumbens 5 min before each morphine session for the transient inhibition of particular anatomical regions. Subcutaneous (s.c.) injection of morphine (2.5 and 5mg/kg) induced place preference. Transient inhibition of the left and/or right side of the shell part of nucleus accumbens reduced morphine place conditioning. However, when both sides of the nucleus were inhibited, inhibition was weaker when compared to the results when only one side was inhibited. Also, the number of compartment crossings in these animals reduced significantly. Nevertheless, the number of rearing occurrences was reduced only when both sides of the shell part of the nucleus accumbens were inhibited. In contrast, the number of sniffing bouts increased in all three groups. The results for the core part of the nucleus accumbens also indicated that place preference was inhibited after transient inhibition of the left, right, and both sides. However, although the number of total compartment crossings was reduced in all experimental groups, the reduction was not statistically significant. The data obtained was similar to the number of rearings, yet the number of sniffing bouts increased in the experimental groups compared to the control. In conclusion, these results confirmed the involvement of the left and right sides and core and shell parts of the nucleus accumbens in morphine place conditioning.

Identification of site of morphine action in pregnant wistar rat placenta tissue: a c(14)-morphine study

OBJECTIVE

In previous studies it has been emphasized that the site of morphine action may be either in the embryo or the placenta. In the present study, we attempt to identify the site of morphine action on the fetal section of Wistar rat placenta by using C(14)-morphine.

MATERIALS AND METHODS

IN THIS STUDY (EXPERIMENTAL), FEMALE WISTAR RATS (WEIGHTS: 170-200 g) were mated with male rats and their coupling times recorded. Experimental groups received daily doses of 0.05 mg/ml of C(14)-morphine in their drinking water. On the 9(th) and14(th) embryonic days, the pregnant rats were anesthetized and the placenta and uterus surgically removed. Placentas were fixed in 10% formalin for two weeks, then processed, sectioned in 5 µm and 25 µm thicknesses, and fixed on glass slides for further evaluation. The 25 µm sections were delivered to black and white film for three days. Films were processed and evaluated with a digital inverse microscope for possible radiological impression. The 5 µm sections were processed for hematoxylin and eosin (H&E) staining, and evaluated by light microscope and MOTIC software.

RESULTS

Our results indicated that the site of action of C(14)-morphine was possibly located on the blood plexus of the fetal portion of the placenta. In addition, oral morphine consumption was shown to inhibit fetal and maternal placental development in the experimental groups.

CONCLUSION

We conclude that morphine's effectiveness on the reduction of embryo growth and development may be via its effects on the blood plexus of the fetal section of the placenta.

Saffron (Crocus sativus) ethanolic extract and its constituent, safranal, inhibits morphine-induced place preference in mice

The effects of saffron ethanolic extract and its constituent, safranal, on the acquisition and expression of morphine-induced place preference (CPP) in male Swiss Webster mice (20-25 g) were investigated in the present study. An unbiased place conditioning method was applied for assessment of morphine reward properties. The saffron extract and safranal were administered intraperitoneally (i.p.) during (acquisition) or after induction (expression) of morphine CPP. In a pilot study, the extract and safranal were alone administered to the animals to assess if they have any reward properties. Subcutaneous (s.c.) of morphine (4 and 8 mg kg(-1)) and extract (50 mg kg(-1); i.p.) induced CPP. Extract (10, 50 and 100 mg kg(-1); i.p.) reduced the acquisition and expression of morphine CPP. The same results were obtained when safranal (1, 5 and 10 mg kg(-1), i.p.) was used. It may be concluded that both ethanolic saffron extract and safranal can inhibit the acquisition and expression of morphine-induced CPP in the mice.

Reduction of metabolic and behavioral signs of acute stress in male Wistar rats by saffron water extract and its constituent safranal

CONTEXT

Saffron extract can inhibit the metabolic disorders induced by stress but the mechanism of action of saffron extract in the central nervous system is not clear.

OBJECTIVE

The present research investigated the effects of saffron water extract and its constituent, safranal on the behavioral and metabolic signs induced by electroshock stress in male Wistar rats (W: 250-300 g).

MATERIALS AND METHODS

Dried saffron material and maceration method was used for extraction. Animals received intra-amygdala (1, 5, and 10 µg/rat) or intraperitoneal (1, 5, and 10 mg/kg) administration of the extract, safranal (Fluka, Germany), or saline 5 or 30 min before stress induction, respectively.

RESULTS

The result showed that stress elevated the corticosterone plasma (115 nmol/L) concentration in the control and intra-amygdala (1, 5, and 10 µg/rat)-treated groups but not in groups that received extract or safranal (55 nmol/L) intraperitoneally (1, 5, and 10 mg/kg). Moreover, anorexia was reduced only in groups that received the extract (1, 5, and 10 mg/kg) or safranal (1, 5, and 10 mg/kg) intraperitoneally (50 sec). Stress increased sniffing, rearing, locomotion, and coping time, which were decreased by intraperitoneal (1, 5, and 10 mg/kg) but not by intra-amygdala (1, 5, and 10 µg/rat) administration of saffron extract and safranal.

DISCUSSION AND CONCLUSION

The results revealed that saffron water extract and safranal had an important impact on the reduction of both metabolic and behavioral signs of stress in male Wistar rats. Moreover, the involvement of the amygdala in this observation can be ruled out.

The effects of low-level laser irradiation on differentiation and proliferation of human bone marrow mesenchymal stem cells into neurons and osteoblasts--an in vitro study

Bone marrow-derived mesenchymal stem cells (BMSCs) are promising for use in regenerative medicine. Several studies have shown that low-level laser irradiation (LLLI) could affect the differentiation and proliferation of MSCs. The aim of this study was to examine the influence of LLLI at different energy densities on BMSCs differentiation into neuron and osteoblast. Human BMSCs were cultured and induced to differentiate to either neuron or osteoblast in the absence or presence of LLLI. Gallium aluminum arsenide (GaAlAs) laser irradiation (810 nm) was applied at days 1, 3, and 5 of differentiation process at energy densities of 3 or 6 J/cm(2) for BMSCs being induced to neurons, and 2 or 4 J/cm(2) for BMSCs being induced to osteoblasts. BMSCs proliferation was evaluated by MTT assay on the seventh day of differentiation. BMSCs differentiation to neurons was assessed by immunocytochemical analysis of neuron-specific enolase on the seventh day of differentiation. BMSCs differentiation to osteoblast was tested on the second, fifth, seventh, and tenth day of differentiation via analysis of alkaline phosphatase (ALP) activity. LLLI promoted BMSCs proliferation significantly at all energy densities except for 6 J/cm(2) in comparison to control groups on the seventh day of differentiation. LLLI at energy densities of 3 and 6 J/cm(2) dramatically facilitated the differentiation of BMSCs into neurons (p < 0.001). Also, ALP activity was significantly enhanced in irradiated BMSCs differentiated to osteoblast on the second, fifth, seventh, and tenth day of differentiation (p < 0.001 except for the second day). Using LLLI at 810 nm wavelength enhances BMSCs differentiation into neuron and osteoblast in the range of 2-6 J/cm(2), and at the same time increases BMSCs proliferation (except for 6 J/cm(2)). The effect of LLLI on differentiation and proliferation of BMSCs is dose-dependent. Considering these findings, LLLI could improve current in vitro methods of differentiating BMSCs prior to transplantation.

Reversal effect of intra-central amygdala microinjection of L-arginine on place aversion induced by naloxone in morphine conditioned rats

BACKGROUND

Role of nitric oxide (NO) on expression of morphine conditioning using a solely classic task has been proposed previously. In this work, the involvement of NO on the expression of opioid-induced conditioning in the task paired with an injection of naloxone was investigated.

METHODS

Conditioning was established in adult male Wistar rats (weighing 200-250 g) using an unbiased procedure. Naloxone (0.05-0.4 mg/kg, i.p.), a selective antagonist of mu-opioid receptor, was administered once prior to morphine response testing. NO agents were administered directly into the central amygdala (CeA) prior to naloxone injection pre-testing.

RESULTS

Morphine (2.5-10 mg/kg, s.c.) produced a significant dose-dependent place preference in experimental animals. When naloxone (0.05-0.4 mg/kg, i.p.) was injected before testing of morphine (5 mg/kg, s.c.) response, the antagonist induced a significant aversion. This response was reversed due to injection of L-arginine (0.3-3 microg/rat), intra-CeA prior to naloxone administration. However, pre-injection of L-NAME (intra-CeA), an inhibitor of NO production, blocked this effect.

CONCLUSION

The finding may reflect that NO in the nucleus participates in morphine plus naloxone interaction.

The effect of morphine consumption on plasma corticosteron concentration and placenta development in pregnant rats

BACKGROUND

Previous studies have shown that morphine consumption during pregnancy may delay embryo development or cause abnormal nervous system function.

OBJECTIVE

The present study focused on the effect of maternal morphine consumption on development of placenta and blood corticosteron concentration in addictive pregnant mothers.

MATERIALS AND METHODS

24 female rats, 170-200g weight, were used. The experimental groups after pregnancy received an oral dose of 0.05 mg/ml of morphine by tap water while the control group received only tap water. On 10(th) and 14(th) day of pregnancy, rats were anesthetized and placenta removed surgically, 1ml blood was collected from each pregnant mother from retro-orbital sinus, the concentration of blood corticosteron was determined by corticosteron Elisa kit after centrifugation. The fixed tissue was processed, sectioned and stained with hematoxylin and eosin. Placenta was studied microscopically according to the thickness of layers, area of blood cisterns, and the number of cells.

RESULTS

Comparing the plasma corticosteron concentration of the treatment and the control groups, not only a severe increase in the treatment group was detected, but also the thickness of maternal and embryonic portions of the placenta at day 10(th) and 14(th) of gestation was different significantly (p≤0.05). Furthermore, an increase in number of cells in maternal and embryonic portion of placenta and a decrease in blood cistern area were demonstrated in both the experimental and the control groups.

CONCLUSION

The effects of morphine, including an increase in blood concentration of corticosteron, in dependent pregnant mothers were seen. Development of placenta in the experimental group was delayed.

Biphasic effects of naloxone in the rats receiving morphine overdose a place preference study

Downward phase of dose-response morphine converted U shape curve was chosen as a base for investigating the effects of different doses of naloxone (0.05-0.4 mg/Kg) on morphine reward/aversion properties using place preference method. First, male Wistar rats (200-220 g) were received morphine (1-7.5 mg/Kg) for place conditioning and marginal dose of morphine (5 mg/Kg) calculated by GraphPad software. In the next part, the animals received different naloxone challenge doses (0.05-0.4 mg/Kg; IP) on the test day. Animals' behavior was monitored using a video camera during the test session. Time spent in each compartment was calculated as the main sign of drug seeking behavior. In addition, numbers of rearing and sniffing as well as locomotion activity for each animal were counted as important dopamine-dependent behavioral signs. More over, the total compartment crossing by each animal as the sign of decision making was also counted. Our results indicated that naloxone showed biphasic effects on the appearance of morphine-induced place preference. The antagonist potentiates the expression of morphine-induced place preference on the dose of 0.05 and 0.4 mg/Kg while inhibits the morphine effect on the dose of 0.1 mg/Kg. On the other hand, the total animal sniffing, rearing, locomotion, and compartment entering were not significantly changed among the groups. It could be concluded that the inhibition of opioid receptors may enhance or inhibit the expression of morphine reward according to the naloxone dose, which in turn indicate the influence of several opioid receptor in this regard. In addition, opioid receptor blocking did not enhance the signs of drug seeking behavior linked to the activity of mesolimbic dopamine system.

Effects of oral morphine on the larvae, pupae and imago development in Drosophila melanogaster

OBJECTIVE

Previous studies, focusing on the effects of abused drugs, have used mice or rats as the main animal models; the present study tries to introduce a simple animal model. For this propose, we investigated the effects of oral morphine consumption by parents on the development of larvae, pupae and imago in Drosophila Melanogaster (D. Melanogaster).

MATERIALS AND METHODS

In this experimental study, twenty male and 20 female D. Melanogaster pupae were housed in test tubes with banana (5 pupae /tube).). Male and female groups each were divided into three experimental group and one control group, which were maintained at 25℃. Morphine (0.2, 0.02, 0.002 mg/ml) was added into the test tubes of the experimental groups. The control group maintained at morphine-free test tube. The male and female groups with the same treatment were coupled and then female fertilization, egg deposit, larval, pupae and imago stages were studied macro and microscopically. The SPSS software (version 9.01) was used for statistical evaluations.

RESULTS

In the experimental groups, in the larvae stage, both increase and decrease of length and surface area in the pupae stage were observed. The number of larvae pupae, and imago was reduced in the experimental groups.

CONCLUSION

The study showed that oral morphine consumption by parents may affect the development of larvae, pupation and imago stages in D. Melanogaster. The results also showed that D. Melanogaster may be a reliable animal model to study on the concerns about abused drugs especially those with opioids.

Milled Stress Reduces Morphine-Induced Locomotion in F2 NMRI Mice

In the present study, the effects of pregnant NMRI mice restraint stress on the responsibility of their children to the behavioral properties of morphine, sulpiride and dextromethorphan were investigated in the F2 generation.

TWENTY FOUR PREGNANT NMRI FEMALE MICE (W

25 g) were divided into the experimental and control groups (n = 12/group). Animals in the experimental group were kept in the restraint cylinder (ID = 6 cm, L = 20 cm) for 60 min/day for 15 consecutive days, while the control group did not receive stress. On the 8(th) day, blood samples were taken from the retro-orbital of both groups for corticosterone measurement (ELYSA method). After the F2 weight gained 20-25 g, their tendency for right-handedness or Left-handedness and response to the new environment was determined by T-maze and open field method, respectively. In addition, the effects of morphine, sulpiride and dextromethorphan on the animals' motor activity were studied. Results showed that plasma corticosterone level in the experimental group was elevated significantly with respect to the controls. In the off-springs, left-handedness was more frequent in both the male and female animals whose mothers experienced restrained stress. In the open field paradigm, however, the females of experimental group showed more activity compared to the others. While the females of the control group showed more response to morphine (50 mg/Kg), interestingly, both male and female animals in the experimental group showed hypo activity to morphine (0.5, 5, and 50 mg/Kg). Similarly, sulpiride (25 and 50 mg/Kg) reduced the animals' activity in both groups, while dextromethorphan did not cause any difference. In conclusion, it can be summarized that stress during the gestation period may change the response to the morphine-induced motor activity, in a sex-dependent manner.

The effects of dopaminergic drugs in the ventral hippocampus of rats in the nicotine-induced anxiogenic-like response

Nicotine an active alkaloid of tobacco has dopaminergic properties. The drug alters anxiety-like behavior in rodents. Ventral hippocampus (VHC) may be a site for modulation of anxiety-like behaviors. The possible involvement of ventral hippocampal dopaminergic receptor mechanism in the nicotine influence on anxiogenic-like response has been investigated in the present study. The effects of apomorphine, sulpiride and SCH23390 on nicotine response in elevated plus maze in rats have been investigated. Intraperitoneal administration of nicotine (0.6mg/kg) decreased percentage of open arm time (%OAT) but not percentage of open arm entries (%OAE) and locomotor activity, indicating an anxiogenic-like response. Intra-hippocampal injection (intra-VHC) of apomorphine, a D(1)/D(2) dopamine receptor agonist (0.1 and 0.2microg/rat) also caused anxiogenic-like effects, but the drug blocked that of nicotine. Intra-VHC administration of the D(2) receptor antagonist, sulpiride (1, 2.5 and 5microg/rat) or the D(1) receptor antagonist, SCH23390 (0.01, 0.1 and 1microg/rat) did not elicit any response. However, pretreatment with sulpiride (1microg/rat) or SCH23390 (0.1microg/rat) decreased nicotine's effect. The results may indicate a modulatory effect for the D(1) and D(2) dopamine receptors of VHC in the anxiogenic-like response induced by nicotine.

The effects of lamotrigine on the acquisition and expression of morphine-induced place preference in mice

The purpose of the present study is to determine the effects of the anticonvulsant drug, lamotrigine, on the acquisition and expression of morphine-induced place preference in mice. Lamotrigine prevents the release of glutamate from presynaptic neurons and inhibits action potential in postsynaptic area by inhibiting presynaptic sodium and calcium channels. Because of such properties, lamotrigine is used for reducing craving for and use of cocaine, alcohol and abused inhalant. So, to determine the effects of lamotrigine on opiates; specifically morphine, 180 male Swiss-Webster mice (20-35 g) were used in this study. Conditioned place preference, was assessed using a biased place conditioning paradigm. In a pilot study the effects of various doses of morphine (2.5, 5 and 10 mg kg(-1)), alone, or in combination with lamotrigine (1, 5 and 25 mg kg(-1)) on the place conditioning paradigm were examined. Animals were injected with the aforementioned doses of lamotrigine 60 min either prior to each morphine injections (acquisition) or prior to the start of the expression on the test day (expression). Administration of different doses of morphine (2.5, 5 and 10 mg kg(-1)) induced conditioned place preference whereas the administration of different doses of lamotrigine (1, 5 and 25 mg kg(-1)) failed to induce place preference. Acquisition and expression of morphine-induced CPP were reduced by lamotrigine at doses of 1, 5 and 25 mg kg(-1) and 5 and 25 mg kg(-1), respectively. Physiological mechanisms of action of lamotrigine and its potential therapeutic use in the treatment of drug-dependence are discussed.

Ascorbic acid antagonizes nicotine-induced place preference and behavioral sensitization in mice

In the present study, the influence of ascorbic acid on the nicotine-induced behavioral sensitization and conditioned place preference was investigated in mice. In the place preference paradigm, intraperitoneal (i.p.) nicotine (1 and 1.5 mg/kg, three drug sessions) but not ascorbic acid (1, 10, 100 and 1000 mg/kg) administration induced place preference. Ascorbic acid administration (10, 100 and 1000 mg/kg, i.p.) reduced both the acquisition and expression of nicotine-induced place conditioning. Locomotor sensitization in mice was produced by intraperitoneal injection of nicotine (0.25 mg/kg) for 7 consecutive days. On the 9th day of the experiments, activity of the mice was recorded after challenge with nicotine (0.1 mg/kg, i.p.). Ascorbic acid (10, 100 and 1000 mg/kg, i.p.) was injected 20 min before each injection of nicotine (acquisition of sensitization) or acutely 20 min before a challenge nicotine injection (expression of sensitization). It was shown that ascorbic acid attenuated the acquisition of nicotine sensitization in a dose-independent manner but the expression of nicotine-induced sensitization was not affected by ascorbic acid. In conclusion, it seems that ascorbic acid may interfere with nicotine-induced place preference and behavioral sensitization in mice.

Effects of Papaver rhoeas extract on the acquisition and expression of morphine-induced behavioral sensitization in mice

In the present study, the effects of a water-alcohol extract of Papaver rhoeas on the acquisition and expression of morphine-induced behavioral sensitization in mice were investigated. The subcutaneous (s.c.) administration of morphine (50 mg/kg) induced locomotor activity in animals, whereas the drug did not show an effect at a dose of 5 mg/kg. On the other hand, intraperitoneal (i.p.) administration of the plant extract (25, 50 and 100 mg/kg) did not show any effect. The locomotor behavioral response was enhanced in mice pretreated with morphine (5 mg/kg, daily x 3 days) alone, indicating that sensitization had developed. Extract (25, 50 and 100 mg/kg, i.p.) administration, 30 min before each of the three daily doses of morphine decreased the development of sensitization. Moreover, intraperitoneal administration of the plant extract (25, 50 and 100 mg/kg) 30 min before the test reduced the expression of morphine-induced behavioral sensitization. The results indicate that administration of the extract of Papaver rhoeas reduced the acquisition and expression of morphine-induced behavioral sensitization in mice.

Effects of ultra-low doses of nicotine on the expression of morphine-induced conditioned place preference in mice

In the present study, the effects of acute administration of nicotine, as well as nicotinic and muscarinic acetylcholine receptor antagonists, on the expression of morphine-induced conditioned place preference, have been investigated in male Swiss-Webster mice. Animals received different doses of morphine 5 days after surgical cannulation in the lateral ventricle. Subcutaneous injections of morphine (2-5 mg/kg) in mouse produced place preference in a dose-dependent manner. Furthermore, both intraperitoneal (0.0006-0.1 mg/kg) and intracerebroventricular (0.007-25 ng) nicotine administration significantly reduced the expression of morphine-induced place preference, in a dose-dependent manner. Nicotine, however, was effective over narrow ultra-low dose ranges (0.0012, 0.0025, 0.005 and 0.01 mg/kg; intraperitoneal) and (0.03, 0.1, 0.3 and 0.6 ng/mouse; intracerebroventricular). In addition, locomotor activity was reduced when higher doses of nicotine [both intraperitoneal (0.02, 0.03 and 0.1 mg/kg) and intracerebroventricular (10 and 24 ng/mouse)] were used. Nicotine alone, however, did not cause motivational effects. Intracerebroventricular injection of hexamethonium (0.03, 0.1 and 0.3 mug/mouse; 10 min before nicotine) diminished the effects of nicotine on morphine-induced conditioned place preference. This effect could neither be obtained by intraperitoneal administration of hexamethonium (1, 5 and 10 mg/kg; 30 min before nicotine), nor be reproduced after either intracerebroventricular or intraperitoneal injection of atropine (a muscarinic receptor antagonist). The antagonists, themselves, did not show any motivational effects when used alone and were unable to affect the expression of morphine-induced conditioned place preference. It appears that ultra-low doses of nicotine can reduce the expression of morphine-induced place preference, and that central nicotinic acetylcholine receptors play a role in this regard.

Theophylline inhibits tolerance and sensitization induced by morphine: a conditioned place preference paradigm study in female mice

The effect of theophylline on reward properties of morphine was examined in the present study. A biased conditioned place preference paradigm was used to study the effects of theophylline on the development of conditioned place preference by morphine in sensitized and tolerant female mice. Subcutaneous injection of morphine (0.5-10 mg/kg) induced conditioned place preference in mice, while intraperitoneal administration of theophylline (2.5-100 mg/kg) did not induce conditioned place preference or conditioned place aversion. Theophylline (2.5-100 mg/kg) in combination with morphine (5 mg/kg), during conditioning sessions, decreased the acquisition of morphine conditioned place preference dose independently. Administration of theophylline (2.5-100 mg/kg) before testing also caused a significant reduction of the expression of morphine-induced conditioned place preference in a dose-independent manner. Administration of morphine (12.5, 25 or 50 mg/kg) daily, for 3 days, produced tolerance to conditioned place preference induced by the drug (5 mg/kg). Administration of theophylline (2.5 and 10 mg/kg) 1 h before morphine (12.5, 25 mg/kg), during development of tolerance, abolished morphine tolerance. A higher dose of theophylline (100 mg/kg), however, did not alter morphine tolerance. In addition, theophylline (2.5, 10 and 100 mg/kg) failed to reduce tolerance to a higher dose of morphine (50 mg/kg). Daily administration of morphine (5 mg/kg) for 3 days followed by a 5-day interval caused sensitization to morphine place conditioning. When theophylline was administered (2.5, 10 and 100 mg/kg) 1 h before morphine (5 mg/kg), during development of sensitization, inhibition of morphine-induced sensitization was demonstrated. The effect of theophylline was dose independent. It is concluded that while theophylline has no effect by itself, it reduced both the acquisition and expression of morphine conditioned place preference. In addition, theophylline reduced the acquisition of morphine conditioned place preference in morphine-sensitized and morphine-tolerant mice.

Effects of Papaver rhoeas extract on the acquisition and expression of morphine-induced conditioned place preference in mice

In the present study, the effects of water-alcohol extract of Papaver rhoeas on the acquisition and expression of morphine-induced conditioned place preference (CPP) in mice were investigated. Subcutaneous (s.c.) administration of morphine (1, 10 and 20 mg/kg) produced place preference. On the other hand, intraperitoneal (i.p.) administration of the plant extract (25, 50 and 100 mg/kg) did not show any effect. Injection of extract (25, 50 and 100 mg/kg, i.p.) 30 min before the morphine administration decreased the acquisition of morphine CPP. Administration of the plant extract (25, 50 and 100 mg/kg, i.p.) 30 min before the test did not change the expression of morphine-induced CPP. It could be concluded that Papaver rhoeas reduced the acquisition but not the expression of morphine-induced conditioned place preference.

Different effects of GABAergic receptors located in the ventral tegmental area on the expression of morphine-induced conditioned place preference in rat

In the present study, an unbiased conditioned place preference paradigm was used to study the effects of intra-ventral tegmental area injections of Gama-amino-butyric acid (GABA)-A and B (GABA(A) and GABA(B)) receptor agonists and antagonists on the expression of morphine-induced conditioned place preference (CPP) in rats. Subcutaneous (s.c.) injections of morphine sulfate (5 mg/kg) induced CPP. Intra-ventral tegmental area administration of the GABA(A) receptor agonist, muscimol (6 microg/rat) reduced the expression of morphine-induced CPP. Muscimol (25 microg/rat) increased the expression of CPP induced by morphine. A reduction of the expression of morphine-induced CPP was observed on intra-ventral tegmental area injection of GABA(A) receptor antagonist bicuculline (25 microg/rat). Bicuculline (10 microg/rat) increased the expression of CPP induced by morphine. Baclofen (12 microg/rat) increased where as (19 and 25 microg/rat) reduced the expression of morphine-induced CPP. Injection of CGP38345 (10, 19, 25 and 50 microg/rat) into the ventral tegmental area significantly reduced the expression of CPP induced by morphine. It is concluded that GABA(A) and GABA(B) receptor subtypes within the ventral tegmental area may have different effects on the expression of morphine-induced CPP.

Effects of maternal oral morphine consumption on neural tube development in Wistar rats

Opiate abuse during pregnancy may result in abnormal nervous system function. In order to evaluate the effects of morphine on the development of the nervous system, the present study focused on the effects of maternal morphine consumption on neural tube development in Wistar rats. Female Wistar rats (250-300 g) were crossed with male rats and coupling time was recorded (embryonic day 0-E0). Experimental groups received 0.1, 0.05, and 0.01 mg/ml of morphine in drinking water daily (14 ml water for each rat). Control group received tap water. On embryonic day 9.5 (E9.5), the animals were anesthetized and the embryos were surgically removed. The embryos were fixed in 10% formalin for 1 week. After this time, weights and lengths (antero-posterior axis--A-P) of the embryos were determined and then tissues were processed, sectioned, and stained in hematoxylin and eosin (H&E). The sections were investigated for neural tube development by light microscope and MOTIC software. The decrease in "A-P" length and embryonic weight for the group that received 0.01 mg/ml morphine was significant. It seems that daily consumption of morphine sulfate could delay neural tube development. In addition, administration of 0.01 mg/ml of morphine led to damage to the regulated neuro-ectoderm layer and its thickness. This study showed that oral morphine consumption leads to neural tube defects, as indicated in the morphometric change and also reduction in weight and length of the embryos. These defects might affect the behavior of the animals.

The effects of nitric oxide on the acquisition and expression of nicotine-induced conditioned place preference in mice

In the present study, the possible role of nitric oxide on the conditioned place preference (CPP) induced by nicotine in mice was investigated. Intraperitoneal (i.p.) injections of nicotine (1 mg/kg) and the nitric oxide (NO) precursor, L-arginine (200 and 500 mg/kg), produced significant place preference. However, injection of mecamylamine (0.05 and 0.1 mg/kg; i.p.) or the NO synthase (NOS) inhibitor, L-Nitro-amino-methyl-ester, L-NAME (5-20 mg/kg; i.p.), had no effect. Ineffective doses of nicotine in combination with ineffective doses of L-arginine produced significant place preference. Administration of L-arginine (50, 100 and 150 mg/kg; i.p.) on the test day reduced the expression of nicotine-induced place preference. Nicotine injection (0.25, 0.5 and 0.75 mg/kg) on the test day reduced the expression of place preference induced by L-arginine, while both mecamylamine (0.05 and 0.1 mg/kg) and L-NAME (5, 10 and 20 mg/kg) inhibited the acquisition of place preference induced by nicotine (1 mg/kg) and L-arginine (200 mg/kg). Moreover, neither of the antagonists reduced the expression of nicotine- or L-arginine-induced place preference. It is suggested that nitric oxide may play an important role in nicotine-induced place preference.

Involvement of nucleus accumbens in L-arginine-induced conditioned place preference in rats

In the present study, the effects of intraperitoneal, intra-accumbal and intra-ventral tegmental area administration of L-arginine and N(G)-nitro-L-arginine methyl-ester (L-NAME) on conditioned place preference behavior were studied. Intraperitoneal (i.p.; 0.5, 1 and 5 mg/kg) and intra-accumbal (intra-NAc; 0.3, 1 and 3 microg/rat), but not intra-ventral tegmental area (intra-VTA; 0.3, 1 and 3 microg/rat) administrations of L-arginine produced a significant place conditioning. Similar injections of L-NAME did not produce any response. However, intraperitoneal pretreatment of the animals with L-NAME (5, 10 and 20 mg/kg), 30 min before L-arginine administration, significantly abolished the acquisition of place conditioning induced by either intraperitoneal or intra-accumbal injection of L-arginine. Moreover, injection of L-NAME (5, 10 and 20 mg/kg) on the test day did not alter the L-arginine response. The results may indicate that L-arginine induces conditioned place preference via an increase in nitric oxide (NO) in the nucleus accumbens.

Effects of Papaver rhoeas extract on the expression and development of morphine-dependence in mice

The problem of drug dependence still remains unresolved. In the present study, the effects of water-alcohol extract of Papaver rhoeas on the expression and acquisition of naloxone-induced jumping and diarrhea in morphine-dependent mice were investigated. Administration of three daily doses of morphine (12.5, 25 and 50 mg/kg) for three days in order to develop dependence to morphine caused a significant and dose-dependent increase in the number of jumping and diarrhea when the animals were challenged with naloxone (4 mg/kg). On the other hand, administration with the plant extract (25, 50 and 100 mg/kg) did not show any effect. Injection of extract (25, 50 and 100 mg/kg) 30 min before the naloxone administration in morphine-dependent mice decreased the number of jumping and diarrhea. Administration of extract (25, 50 and 100 mg/kg) 30 min before morphine injection increased the number of jumping but decreased the diarrhea. It could be concluded that the extract of Papaver rhoeas can ameliorate the withdrawal syndrome in morphine-dependent mice. Therefore, the extract might be useful to treatment of withdrawal signs in opioid addicts.

The role of alpha-adrenoceptor mechanism(s) in morphine-induced conditioned place preference in female mice

It has been shown that the alpha-adrenergic system is involved in some effects of opioids, including analgesia and reward. Gender differences also exist between males and females in response to alpha-adrenergic agents. This study was designed to determine the effects of alpha-adrenoceptor agonists and antagonists on the acquisition or expression of morphine-induced conditioned place preference (CPP) in female mice. The experiments showed that subcutaneous injections of morphine (0.5-8 mg/kg) induced CPP in a dose-dependent manner in mice. Intrapritoneal administration of the alpha-1-adrenoceptor agonist, phenylephrine (0.03, 0.1 and 0.3 mg/kg), and alpha-2 adrenoceptor agonist, clonidine (0.0001, 0.0005 and 0.001 mg/kg), as well as alpha-1-adrenoceptor antagonist, prazosin (0.01, 0.05 and 0.1 mg/kg) or alpha-2 adrenoceptor antagonist, yohimbine (0.005, 0.01 and 0.05 mg/kg) did not induce motivational effects and also did not alter locomotor activity in the animals. In the second set of experiments, the drugs were used before testing on Day 5, to test their effects on the expression of morphine-induced CPP. Intrapritoneal administration of phenylephrine and clonidine decreased the expression of morphine-induced CPP. In contrast, after application of prazosin or yohimbine, the expression of morphine-induced CPP was increased. Administration of lower (0.03 mg/kg) and higher doses of phenylephrine (0.1 and 0.3 mg/kg) during acquisition of morphine CPP decreased and increased the morphine CPP, respectively. Similarly, the administration of prazosin and clonidine decreased while yohimbine increased the morphine CPP. It may be concluded that alpha-adrenoceptor mechanism(s) influence morphine-induced CPP in female mice.

Effects of nitric oxide on morphine self-administration in rat

Previous studies have reported that morphine exerts its effects in part through the release of nitric oxide (NO). In the present study, the effects of acute and chronic administration of the NO precursor, L-arginine and NO synthase (NOS) inhibitor, L-nitro-amino-methyl-ester (L-NAME) on morphine self-administration in rats were investigated. The animals were initially trained to press a lever using food as reinforcer. Rats were surgically prepared with a chronic Silastic catheter implanted in the external jugular vein. Five days after surgery, they were trained to press a lever for drug self-administration. The present data indicate that L-arginine (0.05, 0.1, and 0.15 mg/kg/injection) but not L-NAME (0.05, 0.1, and 0.15 mg/kg/injection) induced self-administration behavior and increased locomotion. The response induced by L-arginine (0.1 mg/kg/injection) was reduced by pretreatment with L-NAME (5, 10, and 15 mg/kg ip). Both the acute (5, 10, and 15 mg/kg ip) and the chronic (200 mg/kg ip; twice daily for 4 days) administration of L-arginine reduced morphine self-administration. However, acute (5, 10, and 20 mg/kg ip) and chronic (50 mg/kg ip; twice daily for 4 days) administration of L-NAME increased morphine self-administration significantly. It can be concluded that NO may have a role in morphine self-administration.

Involvement of dopamine receptors of the dorsal hippocampus on the acquisition and expression of morphine-induced place preference in rats

In the present study, the effects of bilateral intrahippocampal CA1 injections of dopamine receptor agonists and antagonists on the acquisition and expression of morphine-induced place preference were examined in male Wistar rats. Subcutaneous administration of different doses of morphine sulphate (0.5-10 mg/kg) produced a conditioned place preference (CPP) dose-dependently. Using a 3-day schedule of conditioning, it was found that dopamine D1 receptor agonist, SKF 38393 (0.01-1 microg/rat), dopamine D1 receptor antagonist, SCH 23390 (0.25-1 microg/rat), dopamine D(2/3) receptor agonist, quinpirole (0.3-3 microg/rat) or dopamine D2 receptor antagonist, sulpiride (0.04-5 microg/rat) did not produce significant place preference. The administration of SKF 38393 (1 microg/rat) significantly potentiated the acquisition of morphine (0.5 and 2.5 mg/kg)-induced place preference. This potentiation was reversed by SCH 23390 (1 microg/rat) pretreatment. Quinpirole injection (0.3 microg/rat) induced CPP in combination with the lower doses of morphine but decreased the response of the higher doses of morphine. These responses of quinpirole were reversed by sulpiride (5 microg/rat) pretreatment. SCH 23390 or sulpiride reduced the acquisition of morphine (7.5 mg/kg)-induced place preference. The administration of sulpiride, but not other drugs, during acquisition showed an increase in the locomotor activity on the testing days. SKF 38393, SCH 23390 or sulpiride, but not quinpirole when used before testing, reduced the expression of morphine-induced place preference. Sulpiride, but not other drugs, increased locomotion when used before testing. It is concluded that dorsal hippocampal dopamine receptors may play an active role in morphine reward.

Role of nitric oxide in the acquisition and expression of apomorphine- or morphine-induced locomotor sensitization

In the present study, the effects of L-arginine, a nitric oxide (NO) precursor, and N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, on apomorphine- or morphine-induced locomotor sensitization in male albino mice were investigated. Our data showed that subcutaneous (s.c.) injection of apomorphine (2-10 mg/kg) or morphine sulphate (5-50 mg/kg) significantly increased locomotor behaviour in a dose-dependent manner. Intraperitoneal (i.p.) administration of L-arginine (100 mg/kg) increased locomotor activity, whereas L-NAME (20 mg/kg) decreased it. L-Arginine and L-NAME increased and decreased apomorphine- or morphine-induced locomotions, respectively. The locomotor behavioural response was enhanced in mice pretreated with apomorphine (2 mg/kg, daily x3 days) or morphine (10 mg/kg, daily x3 days) alone, indicating that sensitization had developed. Administration of L-arginine 30 min before each of three daily doses of apomorphine or morphine increased the development of sensitization, while administration of L-NAME 30 min before each of three daily doses of apomorphine or morphine decreased the acquisition of sensitization induced by apomorphine or morphine. Administration of L-arginine significantly increased and L-NAME significantly and dose-dependently decreased the expression of both apomorphine- and morphine-induced sensitization. The results indicate that NO may be involved in the acquisition and expression of apomorphine- or morphine-induced sensitization.

Long-term effect of a single dose of sulfur mustard on nerve conduction velocity and electromyography pattern in rat hindlimb

OBJECTIVE

Biological effects of sulfur mustard (SM) on various systems have been investigated in both humans and animals. However, few studies are available on the effect of SM on the peripheral nervous system. In the present study, long-term effects of a single dose of SM on nerve conduction velocity and electromyography (EMG) pattern is evaluated in hindlimb of adult male rats.

METHODS

SM poisoning was induced by two means: subcutaneous injection of 1 and 3.5 mg/kg SM in two experimental groups (1 and 2) and cutaneous application of 8 and 13 mg/kg SM in groups 3 and 4. Sham and control groups received SM vehicle, isopropyl alcohol, and nothing, respectively. Electrophysiological assessments were performed after 26 weeks as follows: sciatic nerve conduction study that included measuring, amplitude, duration, and latency of M-wave, F-wave latency, and EMG study in resting and minimal contraction states.

RESULTS

Results indicate that sciatic nerve conduction velocity did not significantly change in any experimental groups. However, resting EMG records showed some abnormalities very similar to positive sharp waves and fasciculation reported in humans. These abnormalities were observed in 6 of 36 intoxicated rats.

CONCLUSIONS

Although the present data are in favor of axonal degeneration, to rule out the possibility of other types of degeneration, additional thorough studies at ultrastructural level are suggested.

Sulpiride injections into the medial septum reverse the influence of intra-medial septum injection of L-arginine on expression of place conditioning-induced by morphine in rats

Effects of intra-medial septum injections of L-arginine, a precursor of nitric oxide, N(G)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase, and sulpiride, a selective antagonist of dopamine D2 receptor on morphine-induced conditioned place preference (CPP) in male Wistar rats were examined. Using a 3-day schedule of conditioning, morphine (0.5-7.5 mg/kg, s.c.) produced a significant place preference in a dose-dependent manner. The maximum response was observed with 5.0 mg/kg of opioid. Sulpiride (0.3, 1.0 and 3.0 microg/rat), but not L-arginine (0.3, 1.0 and 3.0 microg/rat) or L-NAME (0.3, 1.0 and 3.0 microg/rat), in combination with morphine (5.0 mg/kg), during conditioning, significantly altered morphine-induced CPP. Single doses (0.3, 1.0 and 3.0 microg/rat) of either L-arginine or L-NAME, during conditioning, did not induce CPP. Sulpiride at 0.3-3.0 microg/rat, intra-medial septum, during conditioning, produced a significant conditioned place aversion. Intra-medial septum injections of L-arginine but not L-NAME or sulpiride, 1-2 min before testing, increased the expression of morphine-induced CPP. The administration of sulpiride (0.3, 1.0 and 3.0 microg/rat), but not L-NAME (0.3, 1.0 and 3.0 microg/rat), 1-2 min before the injection of L-arginine (0.3 microg/rat) on day of test, significantly attenuated the response to L-arginine. L-Arginine (0.3-3.0 microg/rat), during conditioning, showed a statistically significant increase in locomotor activity compared with that to control group. Moreover, sulpiride decreased locomotion by itself or in combination with morphine during conditioning and on the test day of morphine CPP. It can be concluded that L-arginine, a precursor of nitric oxide, in the rat median septum may play a role in expression of morphine conditioning due to dopamine release in this area.