Protective Effect of Baclofen on Ovarian Cystogenesis and Morphine-Induced Lipid Profile Change in Female Rats.

Introduction: Morphine induces ovarian cysts that cause obesity and disrupt sex hormone secretion. Baclofen, a gamma-aminobutyric acid receptor agonist, can help regulate sex hormones and reduce harmful blood lipids by protecting against morphine-induced gamma-aminobutyric acid inhibition. We investigated the prophylactic effect of baclofen in rats receiving morphine by comparing with the untreated groups. Materials and Methods: Forty eight female Wistar rats were randomly divided into several groups, including control (saline 1 mL/kg, i.p.), morphine (5 mg/kg, i.p.), baclofen (10, 20, and 30 mg/kg, i.p.), and baclofen (10, 20, and 30 mg/kg) before morphine (5 mg/kg). Twenty four hours after the treatment, blood and serum samples were taken to check the levels of gonadotropins (LH & FSH) and lipid profile. The ovaries and uterus were also studied, and a proinflammatory nitric oxide (NO) diagnostic test was completed. The results were analyzed using analysis of variance (α = 0.05). Results: In comparison with the control group, the levels of LH and not FSH decreased in the morphine group and the number of ovarian cysts was more in the morphine group. These problems were not observed in the group of baclofen alone and baclofen + morphine. However, the triglyceride level increased slightly in the baclofen 30 mg/kg + morphine group. But the LDL level somewhat decreased. The proinflammatory NO system did not show significant activation in the ovary and uterus, except for the baclofen 10 mg/kg + baclofen group. Conclusion: Morphine can cause ovarian cysts by lowering LH but baclofen prophylaxis can protect reproductive properties by adapting major metabolic changes.

Protective effects of L-arginine on Alzheimer's disease: Modulating hippocampal nitric oxide levels and memory deficits in aluminum chloride-induced rat model.

There is evidence that high daily intake of aluminum (Al) is associated with an increased risk of dementia or cognitive decline. We injected L-arginine into the dorsal hippocampus (DH) of an AlCl3-induced Alzheimer's model and studied memory deficit, ß-amyloid (ßA) accumulation, neurodegeneration, and molecular changes. Male Wistar rats were cannulated unilaterally in the DH under a stereotaxic apparatus and a dose of AlCl3 (1-200 µg/rat) was injected into the CA1. After recovery, L-arginine and L-NAME (0.05-25 µg/rat) were injected into CA1 and animals were tested in novelty seeking task. One group received ßA (2 µg/rat, intra CA1) as a reference group. Control groups received saline (1 µL/rat, intra-CA1) and galantamine (25 µg/rat, intra-CA1), respectively. Finally, rats were anesthetized and hippocampal tissues were isolated on ice. Levels of neuronal NO synthase (nNOS), ß-secretase and soluble guanylyl cyclase (sGC) were measured by western blotting. ßA formation and the number of CA1 neurons were assessed by Congo red and Nissl staining. NOS activation by NADPH-diaphorase (NADPH-d) was investigated. All data were analyzed using analysis of variance (ANOVA) at α = 0.05 level. Like ßA, AlCl3 (25 µg/rat) caused accumulation of ßA in the DH and increased stopping of the animal on the novel side (indicating a recall deficit). CA1 neurons decreased, and nNOS and ß-secretase, but not sGC, showed a change consistent with Alzheimer's. However, prophylactic intervention of L-arginine at 3-9 µg/rat was protective, probably by nNOS stimulation in DH, as shown by NADPH-d assay. L-arginine may protect against Alzheimer's by increasing hippocampal NO levels.

Protective Effect of L-Arginine in an Animal Model of Alzheimer's Disease Induced by Intra-Hippocampal Injection of AlCl3.

Background and Objective: Aluminum chloride (AlCl3) can impair spatial memory recovery. We investigated the protective effect of L-arginine, a precursor of nitric oxide (NO), on memory retrieval in an Alzheimer's animal model induced by AlCl3 at intra-hippocampal CA1 using a seeking behavior practice. Materials and Methods: Wistar rats were deeply anesthetized and cannulated at CA1 (AP: -3.8 mm, L: ±2.2 mm, V: 3 mm), and received once AlCl3 (1-200 µg/rat, intra-CA1), on day of cannulation under stereotaxic device. After a week of recovery, they experienced the novelty task with a three-stage paradigm and injected L-arginine (0.05-25 µg/rat) intra-CA1, pretesting. L-NAME, the neuronal NO synthase inhibitor was administered before L-arginine effective doses in the test stage. Also, a reference group exclusively received beta-amyloid 2 µg/rat. Control group solely received saline. Finally, after euthanasia of rat, the hippocampal sample was collected on ice and evaluated by immunohistochemical marking and specific staining. Results: AlCl3 caused novelty-seeking behavior without meaningful change in animal locomotor activity. ßA (2 µg/rat, intra-CA1) affected the rat's grooming, causing it to stop further in the new side. Pretest injection of L-arginine restored behavior in AlCl3-treated rats; however, this effect was stopped by L-NAME pretreatment, indicating NO involvement. CA1 did not show necrotic change due to AlCl3 exposure; however, neurofibrillary tangles were accumulated in the region. Conclusions: Prophylaxis with L-arginine probably due to NO has a protective role against the dangerous effect of AlCl3 on the function of neurons in the cortical hippocampus.

The regulatory role of nitric oxide in morphine-induced analgesia in the descending path of pain from the dorsal hippocampus to the dorsolateral periaqueductal gray.

BACKGROUND: Nitric oxide (NO) levels in brain nuclei, such as the hippocampus and brainstem, are involved in morphine analgesia, but the relationship between the dorsal hippocampus (dH) and the dorsolateral periaqueductal gray matter (dlPAG) needs to be clarified, which is our goal. METHODS: Wistar rats were simultaneously equipped with a stereotaxic device with unilateral guide cannula at dH and dlPAG. After recovery, they were divided into control and experimental groups. Formalin (50 µl of 2.5%) was inoculated into the left hind paw of the rat. Morphine (6 mg/kg) was administered intraperitoneally (i.p.) 10 min before formalin injection. L-Arginine (0.25, 0.5, 1 and 2 µg/rat), and L-NAME (0.25, 0.5, 1 and 2 µg/rat), unrelatedly or with respect in the order of injection were used in the nuclei before morphine injection (i.p.). Activation of the neuronal NO synthase (nNOS) in the brains of all animals was measured using NADPH-diaphorase, a selective biochemical marker of nNOS. RESULTS: Morphine reduced inflammatory pain in the early and late stages of the rat formalin test. The morphine response was attenuated before injection of single L-arginine but not L-NAME in the two target areas. However, the acute phase result was stopped due to L-NAME pretreatment. When L-NAME was injected into dlPAG before injecting L-arginine at dH, the morphine response did not decrease at all, indicating a modulatory role of NO in dlPAG, which was confirmed by NADPH-d staining. CONCLUSIONS: High levels of NO in dlPAG may regulate the pain process in downward synaptic interactions. SIGNIFICANCE: Nitric oxide is involved in the dH and dlPAG in morphine-induced analgesia in the rat formalin test. Morphine has analgesic effects in both phases of the rat formalin test. The morphine response is reduced in two stages by injection of the NO precursor L-arginine but not the nNOS inhibitor L-NAME in the dH and dlPAG. By injecting L-NAME before L-arginine in both nuclei, the morphine-induced response returns in the early stages. Due to the initial injection of L-NAME into dlPAG and the subsequent injection of L-arginine at dH, morphine analgesia is not reduced at all, indicating NO modulation in the pain pathway from dH to dlPAG.

Silver nanoparticles (Ag-NPs) in the central amygdala protect the rat conditioned by morphine from withdrawal attack due to naloxone via high-level nitric oxide.

Repeated injection of morphine during conditioned place preference (CPP) leads to spatial craving due to high-level nitric oxide (NO) in the central nucleus of amygdala (CeA). Silver nanoparticles (Ag-NPs) can produce oxygen-free radicals that lead to NO formation. We aimed to show the Ag-NPs protective effect on naloxone (NLX)-induced morphine withdrawal in the conditioned rats. Wistar rats (300-350 g) were implanted with cannulae in the CeA. After recovery, they were randomly divided into experimental and saline groups. CPP was conducted by three-phase unbiased program. Morphine (0.5-7.5 mg/kg) was injected subcutaneously (s.c.) once/per day during the conditioning phase. Naloxone (NLX) (0.05-0.4 µg/rat) was given, intra-CeA, 10 min before the CPP test. Ag-NPs (0.0001-0.01 µg/rat) were administered alone or prior to the NLX effective dose (0.4 µg/rat), intra-CeA. Conditioning score and withdrawal signs (wet dog shaking and scratching) were obtained and compared with saline group data. All rats' brains were collected in formalin 10% and after 48-72 h stained with NADPH-diaphorase, the NO marker. All data were analyzed by one-way or two-way ANOVA. Morphine (2.5-7.5 mg/kg, s.c.) induced a significant CPP vs. saline (1 mL/kg, s.c.). The single Ag-NPs had no significant effect, whereas the NLX caused meaningful WDS and scratching. However, the NLX pre-treatment in combination with Ag-NPs eliminated these signs. Furthermore, the NO level increased in the CeA. The Ag-NPs may protect the morphine-conditioned rats against the NLX-induced withdrawal symptoms due to high-level NO in the CeA.

Rat's Polycystic Ovary Due to Intraventromedial Hypothalamus Morphine Injection.

BACKGROUND AND OBJECTIVE: The most important alkaloid of opium family, morphine, may show unfavorable effect on the reproductive organs. This research investigated the effect of microinjection of morphine into the rat's ventromedial hypothalamus (VMH) on cystic genesis in the ovary and the health of neurons of VMH. MATERIALS AND METHODS: Female rats (Wistar, weighing 200-250 g) kept under standard conditions were cannulated under anesthesia by Stoelting stereotaxic instrument at the coordinates anterior-posterior: -1.92, ventral: 9, lateral: 0.5. After being recovered, they were microinjected single morphine (0.1-0.4 µg/rat, once intra-VMH) and/or naloxone hydrochloride (0.1-0.4 µg/rat, once intra-VMH) using a 5-µL Hamilton syringe with the polyethylene tubing. The control group solely given physiological saline (1 µL/rat, intra-VMH). Three days after the experiment, both ovary and brain samples were collected from the control and the experimental groups, and they were studied histopathologically. The brain samples were checked out with the aid of the cresyl violet, and the ovaries were stained by the hematoxylin and eosin. The samples were also biometrically examined to compare the ovaries' cystic formations. Also, the number of healthy or injured neurons in the nuclei was compared. RESULTS: The ovaries of morphine-treated rats showed polycystic characteristics in comparison with the control samples. In addition, the brain slices of the morphine-treated rats illustrated a significant decrease in intact neurons. Both mal effects were resolved in the presence of naloxone. CONCLUSION: These results may show that the morphine induces anovulatory infertility probably by hypothalamus-pituitary-ovary axis dysfunction.

Neuroprotective effects of oleuropein against cognitive dysfunction induced by colchicine in hippocampal CA1 area in rats.

Alzheimer's disease is a progressive neurodegenerative disorder with decline in memory. The role of oxidative stress is well known in the pathogenesis of the disease. The purpose of this study was to evaluate pretreatment effects of oleuropein on oxidative status and cognitive dysfunction induced by colchicine in the hippocampal CA1 area. Male Wistar rats were pretreated orally once daily for 10 days with oleuropein at doses of 10, 15 and 20 mg/kg. Thereafter, colchicine (15 µg/rat) was administered into the CA1 area of the hippocampus to induce cognitive dysfunction. The Morris water maze was used to assess learning and memory. Biochemical parameters such as glutathione peroxidase and catalase activities, nitric oxide and malondialdehyde concentrations were measured to evaluate the antioxidant status in the rat hippocampus. Our results indicated that colchicine significantly impaired spatial memory and induced oxidative stress; in contrast, oleuropein pretreatment significantly improved learning and memory retention, and attenuated the oxidative damage. The results clearly indicate that oleuropein has neuroprotective effects against colchicine-induced cognitive dysfunction and oxidative damage in rats.

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.

Differences in morphine-induced antinociception in male and female offspring born of morphine exposed mothers.

OBJECTIVE: Antinociceptive effect of morphine in offspring born of mothers that received saline or morphine during the gestation period was investigated. MATERIALS AND METHODS: Wistar rats (200-250 g) received saline, morphine 0.5 mg/kg or 5 mg/kg during gestation days 14-16. All pups after weaning were isolated treatment/sex dependently and were allowed to fully mature. The antinociceptive effect of morphine was assessed in formalin test. Morphine (0.5-7.5 mg/kg) or saline (1 ml/kg) was injected intraperitoneally 10 min before formalin (50 µl of 2.5% solution in right hind-paw). RESULTS: Male offspring born of saline-treated mothers were less morphine-sensitive than females. On the contrary, male offspring exposed prenatally to morphine (5 mg/kg) were more sensitive to morphine-induced antinociceptive response in formalin test. However, no difference in antinociceptive effect was observed amongst offspring of either sex born of mothers treated with morphine 0.5 mg/kg, identifying a lower dose effect of the opioid. CONCLUSION: The exposure to morphine during the developmental period may result in altered development of tolerance to morphine and thus involved in drug abuse.

Injection of colchicine intra-hippocampal cortical area 1 enhances novelty seeking behavior.

OBJECTIVE: Colchicine, a potent neurotoxin derived of plant has been recently identified as a degenerative toxin of small pyramidal cells in the hippocampal cortical area 1 (CA1). In this study, the effect of the alkaloid intra hippocampal CA1 on the novelty seeking behavior in the conditioning task was measured. MATERIALS AND METHODS: Injections of colchicine (1-75 µg/rat, intra-CA1) were performed in cannulated male Wistar rats while being settled in the stereotaxic apparatus. Control group was solely injected saline (1 µl/rat, intra-CA1). One week later, after recovery, all the animals passed the novelty seeking paradigm using an unbiased conditioning task. They were habituated with the conditioned place preference (CPP) apparatus on day 1. Then they were confined in one part of the CPP box for 3 more days. Finally, the animals were tested in the last day. To evaluate, the possible cell injury effect of the toxin on the pyramidal cells of the CA1 both the motivational staying signal in the parts of the box and the non-motivational locomotive signs of the rats were measured. RESULTS: Based on the present study, the alkaloid caused significant novelty seeking behavior at higher doses. It also affected the compartment entering behavior in the colchicine received group. However, the alkaloid did not show the significant effect on sniffing, rearing or grooming in the rats. CONCLUSION: Injection of colchicine intra-CA1 may impair the neuronal transmission of motivational information by the pyramidal cells in the dorsal hippocampus.

A new approach for aggregation of Paramecium caudatum by nitric oxide.

BACKGROUND AND OBJECTIVES: Nitric oxide (NO) plays a role in thermoregulation and growth of protozoa. This work aimed to add the molecule NO in physiology of protozoa in contact with abused narcotic substances. MATERIALS AND METHODS: A sedative drug, morphine, was infused into a cell chamber containing Paramecia. The cell response to the drug was recorded promptly after drug infusion using a potency protocol provided for the first time at this laboratory. A precursor of NO, L-arginine, was treated jointly with drug to involve the NO system in protozoan performance to drug exposure. Marking of NADPH-diaphorase (NADPH-d) was followed to provide data to explain the mechanisms. RESULTS: Morphine particularly (0.5 to 60 µg/µ1) aggregated the Paramecia. The infusion of L-arginine (1 to 8 µg/µ1) together with morphine potentiated this effect, though, pre-usage of L-NAME (1 to 8 µg/µ1), a blocker of NO production, reversed the response. Notably the activation of NADPH-d in solely morphine or L-arginine plus morphine samples was revealed. However, the expression of marker was attenuated upon pre-infusion with L-NAME. CONCLUSION: This study introduces a new approach to involve NO in physiology of aggregation of Paramecia following exposure to the misused sedative drug, morphine.

Use of colchicine in cortical area 1 of the hippocampus impairs transmission of non-motivational information by the pyramidal cells.

Colchicine, a potent neurotoxin derived from plants, has been recently introduced as a degenerative toxin of small pyramidal cells in the cortical area 1 of the hippocampus (CA1). In this study, the effect of the alkaloid in CA1 on the behaviors in the conditioning task was measured. Injections of colchicine (1,5 µg/rat, intra-CA1) was performed in the male Wistar rats, while the animals were settled and cannulated in a stereotaxic apparatus. In the control group solely injection of saline (1 µl/rat, intra-CA1) was used. One week later, all the animals passed the saline conditioning task using a three-day schedule of an unbiased paradigm. They were administered saline (1 ml/kg, s.c.) twice a day throughout the conditioning phase. To evaluate the possible effects of cell injury by the toxin on the pyramidal cells, both the motivational signals while in the conditioning box and the non-motivational locomotive signs of the treated and control rats were measured. Based on the present study the alkaloid caused no change in the score of place conditioning, but affected both the sniffing and grooming behaviors in the group that received colchicine. However, the alkaloid did not show the significant effect on the rearing or compartment entering in the rats. According to the findings, the intra-CA1 injection of colchicine may impair the neuronal transmission of non-motivational information by the pyramidal cells in the dorsal hippocampus.

Nitric oxide in the hippocampal cortical area interacts with naloxone in inducing pain.

OBJECTIVE: Role of nitric oxide (NO) in reversing morphine anti-nociception has been shown. However, the interaction between NO and naloxone-induced pain in the hippocampus is unknown. The present study aimed to investigate the involvement of molecule NO in naloxone-induced pain and its possible interaction with naloxone into cortical area 1 (CA1) of hippocampus. MATERIALS AND METHODS: Male Wistar rats (250-350 g), provided by Pasteur Institute of Iran, were housed two per cage with food and water ad libitum. The animals' skulls were cannulated bilaterally at coordinates adjusted for CA1 of hippocampus (AP: -3.8; L: ±1.8- 2.2: V: 3) by using stereotaxic apparatus. Each experimental group included 6-8 rats. To induce inflammation pain, the rats received subcutaneous (s.c.) injections of formalin (50 µL at 2.5%) once prior to testing. To evaluate the nociceptive effect of naloxone, the main narcotic antagonist of morphine (0.1-0.4 mg/kg) was injected intraperitoneally (i.p.) 10 min before injection of formalin. Injections of L-arginine, a precursor of NO, and N(G)-Nitro-L-arginine Methyl Ester (L-NAME), an inhibitor of NO synthase (NOS), intra-CA1, were conducted orderly prior to the administration of naloxone. The pain induction was analyzed by analysis of variance (ANOVA). RESULTS: Naloxone at the lower doses caused a significant (P<0.01) pain in the naloxone-treated animals. However, pre-administration (1-2 min) of L-arginine (0.04, 0.08, 0.15, 0.3, 1.0, and 3.0 µg/rat, intra-CA1) reversed the response to naloxone. But, the response to L-arginine was blocked by pre-microinjection (1-2 min) of L-NAME (0.15, 0.3, 1.0, and 3.0 µg/rat), whilst, L-arginine or L-NAME alone did not induce pain behavior. CONCLUSION: NO in the rat hippocampal CA1 area is involved in naloxone-induced nociception.

Nitric oxide-induced polycystic ovaries in the wistar rat.

BACKGROUND: Nitric oxide (NO) involves in polycystic ovary syndrome (PCOS), a cause of infertility in women during the reproductive age. The PCOS is now categorized as an inflammatory phenomenon. The aim of this study was to evaluate the role of NO, a proinflammatory agent, in this syndrome at histological and biochemical levels. MATERIALS AND METHODS: In this experimental study, animals were female Wistar rats (weighing 200-250 g) kept under standard conditions. L-Arginine (50-200 mg/kg), a precursor of NO, was injected intra-peritoneally (i.p.) through a period ranging from 9 to14 days/ once a day. The rats' estrous cycle was studied using Papanicolaou test; those showing phase of Diestrous were grouped into experimental and control groups. The control group solely received saline (1 ml/kg, i.p.) throughout all experiments. To evaluate the inflammatory effect of NO, the rats were treated an anti-inflammatory agent, naloxone hydrochloride (0.4 mg/kg, i.p.), prior to L-arginine. At the end of the treatment period all animals' ovaries were assessed for histopathological and histochemical investigations. Also, activation of NO synthase (NOS) in the experiments was studied using NADPH-diaphorase technique. RESULTS: The ovaries of rats treated with L-arginine showed polycystic characteristics in contrast to those collected from control or naloxone pretreated groups, based on image analysis. A difference in enzyme activation was also shown in the sections that belonged to the groups that received L-arginine when compared with the pre-naloxone and control groups. CONCLUSION: Based on these results, we believe that NO may play a major role in the pathophysiology of PCOS.

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.

Microinjection of l-arginine into corpus callosum cause reduction in myelin concentration and neuroinflammation.

Role of nitric oxide (NO) in inflammationary diseases such as multiple sclerosis (MS) has been proposed previously. We sought to examine if NO plays centrally a key role in MS related phenomena; demyelination or neuroinflammation. Female Wistar rats (weighing 200-250 g) were mounted in a stereotaxic apparatus and received injections of l-arginine aimed at corpus callosum (AP: 1.2, L: ±1.8, V: 3.2). The drug (50-200 µg/rat) was microinjected intra-corpus callosum repeatedly (3-5 times/each per day). Control groups solely received saline (1 µg/rat) into the corpus callosum. The animals were tested for the novelty seeking behavior using the conditioning task. Memory impairment was examined using the shuttle box and Y-maze. l-NAME was pre-injected to l-arginine to involve the NO. All animals' brains were also processed for histological evaluation. l-arginine produced significant changes in the novelty seeking behavior but not in the memory formation, evidenced by passive avoidance and alternation behaviors. Pre-injection of l-NAME reversed the response to l-arginine. Present study further revealed a prominent inflammation as well as myelin elimination in the l-arginine treated rats' brains. These data suggest that the NO infusion in the myelin rich areas such as corpus callosum may lead to MS signs centrally.

Place aversion by morphine in offspring born of female morphine administered wistar rats.

This research was designed to study sexual differences in place conditioning induced by morphine in offspring born of female Wistar rats mated with drug-naïve males. Mothers were exposed to morphine during the 14(th)-16(th) days of gestational. Control dams were simply saline-injected. Female and male virgin offspring born of morphine-treated or saline-treated mothers were separately housed until become fully matured. A 3-day schedule of an unbiased conditioning procedure was used to the induce conditioning to morphine (2.5-7.5 mg/Kg, SC) in the offspring. According to the results, female offspring born of saline-administered mothers were morphine place-conditioned at lower doses of opioid (2.5 mg/Kg) in comparison to the males. An increase in locomotor activity in the females at 7.5 mg/Kg of opioid was also revealed. In contrast, administration of morphine (2.5-7.5 mg/Kg, SC), induced a significant aversion in either sexes of offspring born of morphine-exposed mothers. Moreover, female offspring of this category acquired more pronounced aversion at higher doses of morphine than males. In addition, a significant morphine-dose effect (7.5 mg/Kg, SC) on locomotor activity of these females' offspring was observed. This study may highlight sex differences in conditioning effects induced by morphine between offspring derived of morphine-treated mothers and those of saline-treated.

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.

Verifying of participation of nitric oxide in morphine place conditioning in the rat medial septum using nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d).

BACKGROUND: Role of nitric oxide (NO) in morphine-induced conditioned place preference (CPP) has already been proposed in the rat medial septum (MS), but no molecular evidence has been provided to clear this fact. METHODS: Effects of intraseptal injections of L-arginine and/or NG-nitro-L-arginine methyl ester (L-NAME) on morphine place conditioning in Wistar rats were examined. Morphine (2.5-7.5 mg/kg) was injected s.c. using a three-day schedule of an unbiased place preference. All of the brain samples were examined histochemically by nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), the main marker for NO activation. RESULTS: Morphine induced a significant CPP in the rats. Single injections of L-arginine or L-NAME (0.3, 1.0 and 3.0 µg/rat) did not induce CPP. In addition, co-administration of morphine (5.0 mg/kg) with L-arginine or L-NAME (0.3, 1.0 and 3.0 µg/rat) did not affect morphine response. However, administration of L-arginine (0.3, 1.0 and 3.0 µg/rat) prior to morphine conditioning testing enhanced the expression of morphine response. Moreover, pre-injection of L-NAME (0.3, 1.0 and 3.0 µg/rat) to L-arginine (0.3 µg/rat) did not reverse the response to the agent. The expression of NADPH-d was observed in the rat brain samples treated by L-arginine. A decreased expression of NADPH-d was also observed in rats pre-injected by L-NAME. CONCLUSION: This finding strongly suggests that NO system in the rat MS has an impact on the expression of morphine rewarding, and that the NO participates in place conditioning induced of morphine.

Role of nitric oxide in the rat hippocampal CA1 in morphine antinociception.

In the present study, the effects of intra-hippocampal CA1 injections of l-arginine, a nitric oxide (NO) precursor and N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, on morphine-induced antinociception in rat formalin test were investigated. To induce inflammation pain, formalin (50 microl at 2.5%) was injected into the right hind-paw of male Wistar rats prior to testing. Morphine (3-9 mg/kg) was injected intraperitoneally (i.p.) 10 min before injection of formalin. The present study shows that administration of L-arginine (0.08, 0.15, 0.3, 1.0 and 3.0 microg/rat), but not L-NAME (0.15, 0.3 and 1.0 microg/rat), 5 min before formalin injection reversed morphine-induced antinociception at the early phase of formalin test. However, both drugs blocked morphine antinociception at the late phase of the test, but none of these drugs elicited any response by themselves at the tonic phase when injected alone. Moreover, the response to l-arginine was potentiated by L-NAME pre-treatment. It should be noted that a single injection of both L-arginine and L-NAME showed nociceptive effect at the early phase of the test. The present study reveals an expression of NADPH-diaphorase in the rat brain samples administered by L-arginine. Expression of NADPH-d is decreased in the samples which were pre-injected with L-NAME. This study suggests NO participation in the rat hippocampal CA1 area in morphine-induced antinociception.