The CB1 cannabinoid receptors involvement in anti-epileptic effect of safranal on penicillin-induced epileptiform activity in rats.

Neuroprotective effects for natural products are supported by several studies. In this regard, safranal, a constitute of saffron, has the potential to exert beneficial effects in neuro-logical disorders such as Parkinson's disease, epilepsy, stroke, multiple sclerosis and Alzheimer's disease. Here, we investigated the effect of safranal on penicillin-induced epileptiform activity. Also, the effects of intracerebroventricular (ICV) microinjection of AM251 as a CB1-cannabinoid receptors antagonist to clarify the possible mechanism of safranal were evaluated. Epileptiform activity was induced by intra-cortical administration of penicillin (300 IU, 1.50 µL) in urethane-anesthetized rats. Electrocorticographic recordings were used to analyze the frequency and amplitude of spike waves. Intraperitoneal injections of safranal at doses of 1.00 and 4.00 mg kg-1 significantly reduced both the number and amplitude of spike waves. The ICV microinjection of AM251 (0.50 µg 2.00 µL-1) significantly increased the frequency and amplitude of spike waves. In addition, the anti-epileptic effect induced by administration of safranal at a dose of 4.00 mg kg-1 was partially prevented by ICV microinjection of 0.50 µg 2.00 µL-1 of AM251. The results showed anti-epileptiform activities for safranal. Central CB1 cannabinergic receptors might be involved in the anti-epileptiform activity of safranal.

Design and application of histidine-functionalized ZnCr-LDH nanozyme for promoting bacteria-infected wound healing.

Excessive use of antibiotics can lead to an increase in antibiotic-resistant bacteria, which makes it a serious health threat. Therefore, developing new materials with antibacterial activity, such as nanozymes, has gained considerable attention. Reactive oxygen species (ROS) produced by nanozymes have rapid and effective antibacterial efficacy. Here, histidine (His) modified ZnCr layered double hydroxide (LDH) was synthesized inspired by the natural enzyme, and the enzyme-like activity of His/ZnCr-LDH was tested using a colorimetric method. Then, we developed an acid-enhanced antibacterial method based on the high peroxidase-like activity of His/ZnCr-LDH, and its ROS-generating capability in the presence of glucose oxidase (GOx) and glucose (Glu) as a source of hydrogen peroxide (H2O2). Gluconic acid (GA), the main product of the GOx reaction, provides an acidic environment and promotes ROS generation. The mentioned strategy shows high antibacterial activity at a low minimum inhibitory concentration (MIC) which represents the potential of His/ZnCr-LDH for effective bacterial elimination (3.5 µg mL-1 for S. aureus and 6 µg mL-1 for E. coli). In addition, animal experiments illustrated that the His/ZnCr-LDH can successfully boost the curing of infected wounds. The outcomes indicate that amino acid modified LDHs offer a new strategy for effective bacterial removal in different medical applications.

Exogenous histamine and H 2 receptor activation and H 3 receptor inhibition in nucleus accumbens modulate formalin-induced orofacial nociception through opioid receptors.

It has been demonstrated that the nucleus accumbens (NAc) plays an important role in modulation of nociception due to its extensive connections with different regions of the brain. In addition, this nucleus receives histaminergic projections from tuberomammillary nucleus. Considering the role of the central histaminergic system in nociception, the effect of histamine and its H 2 and H 3 receptors agonist and antagonist microinjections into the NAc on orofacial formalin nociception was investigated. In male Wistar rats, using stereotaxic surgery, two guide cannulas were bilaterally implanted into the right and left sides of the NAc. Diluted formalin solution (1.5%, 50 µl) injection into the vibrissa pad led to orofacial nociception. Immediately after injection, face rubbing was observed at 3-min blocks for 45 min. Orofacial formalin nociception was characterized by a biphasic nociceptive response (first phase: 0-3 min and second phase: 15-33 min). Microinjections of histamine (0.5 and 1 µg/site), dimaprit (1 µg/site, H 2 receptor agonist) and thioperamide (2 µg/site, H 3 receptor antagonist) attenuated both phases of formalin orofacial nociception. Prior microinjection of famotidine (2 µg/site) inhibited the antinociceptive effects of dimaprit (1 µg/site). Furthermore, comicroinjection of thioperamide (2 µg/site) and immepip (1 µg/site) prevented thioperamide (2 µg/site)-induced antinociception. Naloxone (2 µg/site) also prevented histamine, dimaprit- and thioperamide-induced antinociception. The results of this study demonstrate that at the level of the NAc, histamine and its H 2 and H 3 receptors are probably involved in the modulation of orofacial nociception with an opioid system-dependent mechanism.

Cerebellar fastigial nucleus histamine and its H2 but not H1 receptors might inhibit acetic acid-induced visceral nociception and improve motor coordination in rats: role of opioid system.

The cerebellum and its deep nuclei contribute to the regulation of important functions including motor coordination and pain. Histamine modulates some functions of the fastigial nucleus (FN) such as motor coordination. In this study, by application of histamine and activation of its H1 and H2 receptors, the FN processing of visceral pain, general locomotor activity and motor coordination were targeted. The possible mechanism of action was followed by the inhibition of opioid receptors. The right and left sides of the FN were surgically implanted with guide cannulas. Immediately after an intraperitoneal injection of acetic acid (1.00 mL, 1.00%), the first writhing onset latency and the writhing number over 60 min were recorded. Open-field and rotarod tests were applied for general locomotor and motor coordination assessment, respectively. Histamine and dimaprit (H2 receptor agonist) increased first writhing onset latency, decreased the writhing number and increased falling time from the rod. These effects were prevented by ranitidine (H2 receptor antagonist) pre-treatment. Significant alterations were not observed by histamine H1 receptor agonist (2-pyridylethylamine) and antagonist (mepyramine). Naloxone, with no effect on falling time from the rod, inhibited the antinociceptive effects of histamine and dimaprit. Beam break number was not affected by the above-mentioned treatments. Based on the results, it can be suggested that histamine H2, but not H1 receptors at the FN might have had an inhibitory role on acetic acid-induced visceral pain and improved motor coordination. The antinociception, but not motor coordination might be mediated by FN opioid receptors.

Histamine and its H 1 receptors in the ventral pallidum mediate formalin-induced pain-related behaviors through this region and spinal cord opioid receptors.

Many structures of the central nervous system recruit different neurotransmitters in pain processing. This study focused on the contribution of histamine and its H 1 receptors in the ventral pallidum (VP) in mediating pain-triggered behaviors. Intra-VP microinjection of histamine and 2-pyridylethylamine (2-PEA, a histamine H 1 receptor agonist) at the same doses of 0.5 and 1 µg/200 nl reduced both the first and second phases of licking/biting duration as well as flinching number induced by intra-plantar (ipl) injection of formalin (2.5%, 50 µl). Premicroinjection of mepyramine (a histamine H 1 antagonist, 2 µg/200 nl) into the VP antagonized the suppressive effects of 1 µg/200 nl histamine and 2-PEA on licking/biting and flinching behaviors. The possible mechanisms of the above-mentioned pain-reducing effects were followed by intra-VP and intrathecal administration of naloxone (an opioid receptor antagonist). Naloxone (2 µg/200 nl) preadministration into the VP inhibited attenuating effects of histamine and 2-PEA on both the licking/biting and flinching behaviors, whereas intrathecal injection of naloxone only inhibited their suppressing effects on flinching behavior. None of the treatments used in this study altered the animal's motor activity. The obtained results may reveal the role of histamine and its activated H 1 receptor in the VP in suppressing the pain behaviors caused by formalin. Opioid receptors in the VP and spinal cord may contribute to these functions.

Medial prefrontal cortex nitric oxide modulates neuropathic pain behavior through mu opioid receptors in rats.

Background: The neocortex, including the medial prefrontal cortex (mPFC), contains many neurons expressing nitric oxide synthase (NOS). In addition, increasing evidence shows that the nitric oxide (NO) and opioid systems interact in the brain. However, there have been no studies on the interaction of the opioid and NO systems in the mPFC. The objective of this study was to investigate the effects of administrating L-arginine (L-Arg, a precursor of NO) and N(gamma)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NOS) into the mPFC for neuropathic pain in rats. Also, we used selective opioid receptor antagonists to clarify the possible participation of the opioid mechanism. Methods: Complete transection of the peroneal and tibial branches of the sciatic nerve was applied to induce neuropathic pain, and seven days later, the mPFC was cannulated bilaterally. The paw withdrawal threshold fifty percent (50% PWT) was recorded on the 14th day. Results: Microinjection of L-Arg (2.87, 11.5 and 45.92 nmol per 0.25 µL) increased 50% PWT. L-NAME (17.15 nmol per 0.25 µL) and naloxonazine (an antagonist of mu opioid receptors, 1.54 nmol per 0.25 µL) inhibited anti-allodynia induced by L-Arg (45.92 nmol per 0.25 µL). Naltrindole (a delta opioid receptor antagonist, 2.45 nmol per 0.25 µL) and nor-binaltorphimine (a kappa opioid receptor antagonist, 1.36 nmol per 0.25 µL) were unable to prevent L-Arg (45.92 nmol per 0.25 µL)-induced antiallodynia. Conclusions: Our results indicate that the NO system in the mPFC regulates neuropathic pain. Mu opioid receptors of this area might participate in pain relief caused by L-Arg.

Behavioral and receptor expression studies on the primary somatosensory cortex and anterior cingulate cortex oxytocin involvement in modulation of sensory and affective dimensions of neuropathic pain induced by partial sciatic nerve ligation in rats.

BACKGROUND: Brain cortical areas are involved in processing of sensory, affective and cognitive aspects of pain. In the present study, microinjection effects of oxytocin and L-368,899 (an oxytocin receptor antagonist) into the primary somatosensory cortex (S1) and anterior cingulate cortex (ACC) were investigated on sensory and affective aspects of neuropathic pain. METHODS: Neuropathic pain was induced by partial sciatic nerve ligation (PSNL). Seven days later, right and left sides of S1 and ACC were surgically implanted with guide cannulas. Sensory (day 14) and affective (day 17) dimensions were recorded using von Frey filaments and place escape avoidance paradigm, respectively. The S1 and ACC oxytocin receptor protein expression were also determined. RESULTS: The S1 and ACC oxytocin suppressed PSNL-induced mechanical allodynia, whereas PSNL-induced aversion was attenuated by ACC oxytocin. In the S1, alone L-368,899 with no effect on aversion increased mechanical allodynia, whereas, in the ACC, this treatment increased both mechanical allodynia and aversion. Pre-treatment with L-368,899 prevented oxytocin-induced anti-allodynia and anti-aversion. Oxytocin and L-368,899 did not alter mechanical allodynia in intact and sham groups. All the above-mentioned treatments did not change crossing number. The density of oxytocin receptors in the S1 and ACC of PSNL group was increased 1.5-2 folds in comparison to intact and sham groups. CONCLUSIONS: The results of the present study explained that the ACC and S1 oxytocin ameliorated sensory component of neuropathic pain, whereas affective component was attenuated only by ACC oxytocin. These effects might be related to the PSNL-increased oxytocin receptor expression in the S1 and ACC.

Central H2 histaminergic and alpha-2 adrenergic receptors involvement in crocetin-induced antinociception in orofacial formalin pain in rats.

Previous findings have shown that saffron (Crocus sativus L.) extract and its active constituents produce antinociceptive effects in the rat models of orofacial pain. In the present study, the central H2 histaminergic and alpha-2 adrenergic receptors involvement in crocetin-induced antinociception in orofacial formalin pain in rats was evaluated. The guide cannula was implanted into the fourth ventricle in ketamine-xylazine anesthetized rats. Subcutaneous injection of a diluted formalin solution (1.50%; 50.00 µL) into a vibrissae pad was used as a model of orofacial pain. Face rubbing behavior durations were recorded at 3 min blocks for 45 min. Formalin produced a biphasic pain response (first phase: 0-3 min and second phase: 15-33 min). Intra-fourth ventricle injections of crocetin (5.00 and 10.00 µg µL-1) suppressed, whereas yohimbine (10.00 µg µL-1) and naloxone (10.00 µg µL-1) increased the intensity of both phases of pain. Crocetin-induced antinociception was not prevented by central pretreatment with naloxone. However, the antinociceptive effect of crocetin (5.00 µg µL-1) was inhibited by prior administration of famotidine (10.00 µg µL-1) and yohimbine (10.00 µg µL-1). Our study showed that injection of crocetin into the cerebral fourth ventricle attenuated formalin-induced orofacial pain in rats. Central H2 histaminergic and alpha-2 adrenergic receptors, but not opioid receptors, might be involved in crocetin-induced antinociception.

Medial prefrontal cortex diclofenac-induced antinociception is mediated through GPR55, cannabinoid CB1, and mu-opioid receptors of this area and periaqueductal gray.

Supraspinal mechanisms of non-steroidal anti-inflammatory drug (NSAID)-induced antinociception are not well understood. In the present study, the possible antinociceptive mechanisms induced by intra-medial prefrontal cortex (intra-mPFC) microinjection of diclofenac were investigated after blockade of GPR55, cannabinoid CB1, and mu-opioid receptors in this area and ventrolateral periaqueductal gray (vlPAG). For drug delivery, unilateral (left side) of mPFC and bilateral (right and left sides) of vlPAG were surgically cannulated. Formalin test was induced by subcutaneous injection of a diluted formalin solution into the right vibrissa pad. A typical biphasic (neurogenic and inflammatory phases) pain behavior was produced following formalin injection. Microinjection of diclofenac (2.5, 5, and 10 µg/0.25 µL) into the mPFC suppressed both phases of pain. Intra-mPFC microinjection of naloxonazine (a mu-opioid receptor antagonist, 1 µg/0.25 µL) and AM251 (a cannabinoid CB1 receptor antagonist, 1 µg/0.25 µL) increased both phases of pain intensity. In addition, intra-mPFC-microinjected diclofenac-induced antinociception was inhibited by prior intra-mPFC and intra-vlPAG administration of naloxonazine and AM251. On the other hand, intra-mPFC and intra-vlPAG microinjection of AM251 (0.25 µg/0.25 µL) decreased pain severity which was inhibited by prior administration of ML193. The above-mentioned drugs did not alter locomotor activity. In conclusion, diclofenac suppressed both the neurogenic and inflammatory phases of formalin-induced orofacial pain at the level of mPFC. GPR55, cannabinoid CB1, and mu-opioid receptors of the mPFC and vlPAG might be involved in the mPFC analgesic effects of diclofenac.

Medial prefrontal cortex oxytocin-opioid receptors interaction in spatial memory processing in rats.

Medial prefrontal cortex (mPFC), a forebrain structure, is involved in many brain functions such as learning and memory. In the present study, the effect of intra-mPFC microinjection of oxytocin, atosiban, morphine and naloxone was investigated on memory processing. Two guide cannulas were implanted into the right and left sides of the mPFC in ketamine and xylazine-anesthetized rats. To assess spatial memory function MWM test was performed by four training sessions of four trials. On day 5, a probe test was conducted after drugs microinjection. Significant differences were observed in learning activities during training days before microinjection of drugs. Intra-mPFC microinjections of oxytocin (5 and 10 ng/site) significantly increased memory related activities. This effect of oxytocin was inhibited by prior microinjection of atosiban (20 ng/site). On the other hand, morphine microinjection at doses of 5 and 10 µg/site into the mPFC significantly decreased memory related activities that were prevented by prior administration of naloxone (5 µg/site) and oxytocin (5 and 10 ng/site). In addition, intra-mPFC combined microinjections of low doses of oxytocin (2.5 ng/site) and naloxone (1 µg/site) improved memory function. By increasing the doses of oxytocin (5 ng/site) and naloxone (5 µg/site), a more documented improving effect was observed. These results showed that memory performance was impaired by activation of mPFC opioid receptors in rats. In addition, oxytocin in the mPFC improved memory function and prevented memory impairment-induced by morphine. Moreover, an interaction between oxytocin and opioid systems was also appeared in the present study.

Safranal, a constituent of saffron, exerts gastro-protective effects against indomethacin-induced gastric ulcer.

AIMS: Several natural products have been evaluated for management of gastric ulcer induced by non-steroidal anti-inflammatory drugs. Safranal, a plant-derived chemical, has a potent antioxidant and anti-inflammatory properties. The present study was aimed to evaluate possible gastro-protective effects of safranal against indomethacin-induced gastric ulcer in rats. Lansoprazole (a proton pump inhibitor) was used as a reference drug. MATERIALS AND METHODS: Thirty rats were divided into five groups. Groups 1 and 2 received vehicle. Groups 3, 4 and 5 treated with 0.063, 0.25 and 1 mg/kg safranal. Group 6 received 30 mg/kg lansoprazole. All groups except of group 1 received indomethacin (50 mg/kg) ingestion. Six hours later, animals were euthanized and their stomachs were removed. Gastric contents volume and pH were measured. Gastric ulcer area and protective index were evaluated using image J software. Histological changes were evaluated by light microscope. Malondialdehyde (MDA) level, superoxide dismutase (SOD) activity, total antioxidant capacity (TAC) content, tumor necrosis factor-alpha (TNF-α) and Caspase-3 levels were determined in the gastric tissue. KEY FINDINGS: Safranal and lansoprazole normalized gastric volume and pH, reduced gastric ulcer area and produced gastric protection. Indomethacin-induced histological changes and tissue biochemical alterations were ameliorated by the above-mentioned treatments. SIGNIFICANCE: The results of the present study suggest the involvement of anti-secretory, anti-oxidant, anti-inflammatory and anti-apoptotic mechanisms in gastro-protective effect of safranal. In addition, gastro-protective effect of safranal was comparable to lansoprazole.

Carnosine improves functional recovery and structural regeneration after sciatic nerve crush injury in rats.

AIMS: Peripheral nerve injury represents a substantial clinical problem with insufficient or unsatisfactory treatment options. Current researches have extensively focused on the new approaches for the treatment of peripheral nerve injuries. Carnosine is a naturally occurring pleotropic dipeptide and has many biological functions such as antioxidant property. In the present study, we examined the regenerative ability of carnosine after sciatic nerve crush injury using behavioral, biochemical, histological and ultrastructural evaluations. MATERIALS AND METHODS: Seventy-two rats were divided into six groups including control, sham, crush and carnosine (10, 20 and 40 mg/kg) groups. Crush injury in left sciatic nerve was induced by a small haemostatic forceps. Carnosine was administered for 15 consecutive days after induction of crush injury. Sciatic functional index (SFI) was recorded weekly. Histopathological and ultrastructural evaluations were made using light and electron microscopes, respectively. Sciatic nerve tissue malondialdehyde (MDA), superoxide dismutase (SOD) and tumor necrosis factor-alpha (TNF-α) levels were measured. Gastrocnemius muscle weight was determined. KEY FINDINGS: Carnosine at the doses of 20 and 40 mg/kg accelerated SFI recovery. Wallerian degeneration severity and myelinated fibers density, myelin sheath thickness and diameter as well as ultrastructural changes of myelinated axons were improved. It also recovered nerve tissue biochemical (MDA, SOD and TNF-α) changes induced by crush injury. Muscle weight ratio was reached to near normal values. Our results suggest a regenerative effect of carnosine. Inhibition of oxidative stress and inflammatory pathways, along with provocation of myelination and prevention of muscular atrophy might be involved in this effect of carnosine. SIGNIFICANCE: Carnosine treatment might be considered as a therapeutic agent for peripheral nerve regeneration and its functional recovery.

A behavioral evaluation of the effects of ingestion of Linguatula serrata nymphs in rats.

Nasopharyngeal linguatuliasis known as Halzoun or Marrara syndrome occurs following ingestion of raw or undercooked viscera, including lymph nodes, liver and lung of infected animals. The present study was aimed to investigate the behavioral changes induced by ingestion of Linguatula serrata nymphs in rats. For this purpose, 24 rats were divided into four groups and orally ingested with 0 (control), 15, 30 and 60 L. serrata nymphs, respectively. Sneezing, mouth and tongue movements and mouth opening numbers were counted and the duration of mouth and nose grooming was measured at 10-min blocks for 30 min. Ingestion of 0 (normal saline) number of nymph produced negligible behaviors, whereas 15, 30 and 60 numbers of nymphs increased the above-mentioned behaviors when compared to normal saline (0 nymph) group. In this context, 60 number of nymphs produced more behavioral changes than 15 nymphs. We concluded that ingestion of L. serrata nymphs can produce behavioral changes in orofacial area in rats.

Involvement of central opiate receptors in modulation of centrally administered oxytocin-induced antinociception.

OBJECTIVES: Oxytocin is involved in modulation of many brain-mediated functions. In the present study, we investigated the central effects of oxytocin and its receptor antagonist, atosiban on inflammatory pain. The contribution of opiate receptors was explored using non-selective and selective antagonists. MATERIALS AND METHODS: The fourth ventricle of the brain of anesthetized rats was implanted with a guide cannula. Inflammatory pain in the orofacial region was induced by subcutaneous (SC) injection of formalin into the vibrissa pad, and time duration of face rubbing behavior was measured for 45 min. RESULTS: A typical biphasic pain was observed after formalin injection. This biphasic pain behavior was attenuated by intra-fourth ventricle administration of oxytocin (12.5, 50, and 200 ng/rat). Central prior administration of 400 ng/rat atosiban (an oxytocin receptor antagonist), naloxone (a non-selective opiate receptor antagonist), naloxonazine (a selective µ-opiate receptor antagonist), and nor-binaltorphimine (a selective κ-opiate receptor antagonist), but not naltrindole (a δ-opiate receptor antagonist), prevented oxytocin-induced (200 ng/rat) antinociception. Except for naltrindole, other antagonists increased pain intensity when used alone. Above-mentioned drugs did not alter locomotor activity. CONCLUSION: Oxytocin, as a neuropeptide neurotransmitter, may be involved in the supraspinal modulation of inflammatory pain through µ- and κ-, but not δ-opiate receptors.

Role of ventrolateral orbital cortex muscarinic and nicotinic receptors in modulation of capsaicin-induced orofacial pain-related behaviors in rats.

Acetylcholine, as a major neurotransmitter, mediates many brain functions such as pain. This study was aimed to investigate the effects of microinjection of muscarinic and nicotinic acetylcholine receptor antagonists and agonists into the ventrolateral orbital cortex (VLOC) on capsaicin-induced orofacial nociception and subsequent hyperalgesia. The right side of VLOC was surgically implanted with a guide cannula in anaesthetized rats. Orofacial pain-related behaviors were induced by subcutaneous injection of a capsaicin solution (1.5µg/20µl) into the left vibrissa pad. The time spent face rubbing with ipsilateral forepaw and general behavior were recorded for 10min, and then mechanical hyperalgesia was determined using von Frey filaments at 15, 30, 45 and 60min post-capsaicin injection. Alone intra-VLOC microinjection of atropine (a muscarinic acetylcholine receptor antagonist) and mecamylamine (a nicotinic acetylcholine receptor antagonist) at a similar dose of 200ng/site did not alter nocifensive behavior and hyperalgesia. Microinjection of oxotremorine (a muscarinic acetylcholine receptor agonist) at doses of 50 and 100ng/site and epibatidine (a nicotinic acetylcholine receptor agonist) at doses of 12.5, 25, 50 and 100ng/site into the VLOC suppressed pain-related behaviors. Prior microinjections of 200ng/site atropine and mecamylamine (200ng/site) prevented oxotremorine (100ng/site)-, and epibatidine (100ng/site)-induced antinociception, respectively. None of the above-mentioned chemicals changed general behavior. These results showed that the VLOC muscarinic and nicotinic acetylcholine receptors might be involved in modulation of orofacial nociception and hypersensitivity.

Intra-hippocampal microinjection of oxytocin produced antiepileptic effect on the pentylenetetrazol-induced epilepsy in rats.

BACKGROUND: In addition to its role as a circulating hormone, oxytocin can also act as a neurotransmitter and a neuromodulator within the brain. In this study, we investigated the intra-hippocampal effect of oxytocin on an experimental seizure model induced by pentylenetetrazole (PTZ) in rats. We also used atosiban (oxytocin antagonist), diazepam and flumazenil (gamma-aminobutyric acid or GABA-benzodiazepine receptor agonist and antagonist, respectively) to clarify the involved mechanism. METHOD: In ketamine-xylazine anesthetized rats, the right and left sides of the dorsal hippocampus (CA1) were implanted with two guide cannulas. Epileptic behaviors were induced by intraperitoneal (ip) injection of PTZ (60mg/kg), and the latency time to onset of first myoclonic jerk, and the duration of epileptic seizures were determined for 30min. RESULTS: Intra-hippocampal microinjections of oxytocin at doses of 10 and 20ng/site, diazepam (100 and 200ng/site) and co-administration of their ineffective doses significantly (p<0.01) increased the onset of first myoclonic jerk and decreased duration of epileptic seizure. Antiepileptic effects of oxytocin (20ng/site) were inhibited by atosiban (20 and 40ng/site) and flumazenil (100 and 200ng/site) pretreatments. On the other hand, prior administration of flumazenil (100 and 200ng/site) and atosiban (20 and 40ng/site) prevented the antiepileptic effects induced by diazepam (100 and 200ng/site). CONCLUSIONS: The results of the present study showed that at the level of the hippocampus oxytocin suppressed the severity of epileptic behaviors. A hippocampal GABA-benzodiazepine receptor mechanism may be involved in antiepileptic effect of oxytocin.

Role of µ-opioid receptor in parafascicular nucleus of thalamus on morphine-induced antinociception in a rat model of acute trigeminal pain.

The parafascicular nucleus (PFN) of thalamus, as a supraspinal structure, has an important role in processing of nociceptive information. In addition, µ-opioid receptor contributes to supraspinal modulation of nociception. In the present study, the effects of microinjection of naloxone (a non-specific opioid-receptor antagonist) and naloxonazine (a specific µ-opioid receptor antagonist) were investigated on morphine-induced antinociception in a rat model of acute trigeminal pain. Right and left sides of PFN of thalamus were implanted with two guide cannulas. Acute trigeminal pain was induced by local corneal surface application of hypertonic saline and the number of eye wipes as a pain index was recorded for 30 sec. Microinjection of morphine at doses of 1, 2 and 4 µg per site significantly (p < 0.05) decreased the number of eye wipes. Alone microinjection of naloxone (4 µg per site) and naloxonazine (1 and 2 µg per site) significantly (p < 0.05) increased corneal pain severity. Prior microinjection of naloxone (2 and 4 µg per site) and naloxonazine (1 and 2 µg per site) significantly (p < 0.05) prevented the antinociceptive effect induced by morphine (4 µg per site). All the above-mentioned chemicals did not alter locomotor behavior in an open-field test. The results of the present study showed an antinociceptive effect of morphine at the PFN level of thalamus. Mu-opioid receptor of the PFN of thalamus may be involved in morphine-induced antinociception.

Effects of intra-hippocampal microinjection of vitamin B12 on the orofacial pain and memory impairments induced by scopolamine and orofacial pain in rats.

In the present study, we investigated the effects of microinjection of vitamin B12 into the hippocampus on the orofacial pain and memory impairments induced by scopolamine and orofacial pain. In ketamine-xylazine anesthetized rats, the right and left sides of the dorsal hippocampus (CA1) were implanted with two guide cannulas. Orofacial pain was induced by subcutaneous injection of formalin (1.5%, 50µl) into the right vibrissa pad, and the durations of face rubbing were recorded at 3-min blocks for 45min. Morris water maze (MWM) was used for evaluation of learning and memory. Finally, locomotor activity was assessed using an open-field test. Vitamin B12 attenuated both phases of formalin-induced orofacial pain. Prior administration of naloxone and naloxonazine, but not naltrindole and nor-binaltorphimine, prevented this effect. Vitamin B12 and physostigmine decreased latency time as well as traveled distance in Morris water maze. In addition, these chemicals improved scopolamine-induced memory impairment. The memory impairment induced by orofacial pain was improved by vitamin B12 and physostigmine used alone. Naloxone prevented, whereas physostigmine enhanced the memory improving effect of vitamin B12 in the pain-induced memory impairment. All the above-mentioned chemicals did not alter locomotor activity. The results of the present study showed that at the level of the dorsal hippocampus, vitamin B12 modulated orofacial pain through a mu-opioid receptor mechanism. In addition, vitamin B12 contributed to hippocampal cholinergic system in processing of memory. Moreover, cholinergic and opioid systems may be involved in improving effect of vitamin B12 on pain-induced memory impairment.

The role of histamine H1, H2 and H3 receptors of ventral posteromedial nucleus of thalamus in modulation of trigeminal pain.

Histamine receptors are involved in supraspinal modulation of pain. In the present study, we investigated the effects of microinjection of histamine H1, H2 and H3 receptor antagonists and agonists into the ventral posteromedial (VPM) nucleus of the thalamus on two models of trigeminal pain. Right and left sides of VPM were implanted with two guide cannulas. Corneal pain was induced by local corneal surface application of hypertonic saline and the number of eye wipes was recorded. The duration of face rubbing, as an orofacial pain measure, was recorded after subcutaneous (s.c.) injection of capsaicin into the vibrissa pad. 2-pyridylethylamine (2-PEA, a histamine H1 receptor agonist, 4µg/site) and dimaprit (a histamine H2 receptor agonist, 1 and 4µg/site) suppressed corneal and orofacial pains. Mepyramine (a histamine H1 receptor antagonist) and ranitidine (a histamine H2 receptor antagonist) at the similar doses of 0.5, 2 and 8µg/site alone had no effects on trigeminal pain. Prior microinjection of mepyramine and ranitidine at a similar dose of 8µg/site inhibited the antinociceptive effects of 2-PEA (4µg/site) and dimaprit (4µg/site), respectively. Immepip (a histamine H3 receptor agonist, 1 and 4µg/site) increased, and thioperamide (a histamine H3 receptor antagonist, 2 and 8µg/site) attenuated nociceptive responses. Prior microinjection of thioperamide (8µg/site) prevented immepip (4µg/site)-induced nociception. These chemicals did not change locomotor behavior. It is concluded that post-synaptic histamine H2, and to a lesser extent H1, receptors and pre-synaptic histamine H3 receptor may be involved in VPM modulation of trigeminal pain.

The effects of crocin and safranal on the yawning induced by intracerebroventricular injection of histamine in rats.

OBJECTIVE: Crocin and safranal, as the major constituents of saffron, have many biological activities. This study investigated the effects of crocin and safranal on yawning response induced by intracerebroventricular (i.c.v.) injection of histamine in rats. MATERIALS AND METHODS: In ketamine/xylazine-anesthetized rats, a guide cannula was implanted in the right ventricle of the brain and yawning induced by i.c.v. injection of histamine. Crocin and safranal were intraperitoneally (i.p.) injected alone and before i.c.v. injection of histamine. RESULTS: Histamine at the doses of 10 and 20 µg/rat produced yawning. Mepyramine (a histamine H1 receptor antagonist) 40 µg/rat significantly (p<0.05) prevented histamine (20 µg/rat)-induced yawning. Crocin (30 mg/kg) and safranal (1 mg/kg) significantly (p<0.05) increased histamine (10 µg/rat)-induced yawning. Crocin and safranal also induced yawning when injected before mepyramine plus histamine administration. CONCLUSION: The results of the present study showed a yawning-inducing effect for central histamine, which was inhibited by mepyramine. Crocin and safranal increased histamine-induced yawning, and also produced yawning when the histamine action is blocked.