Wet Dog Shakes Research Articles

Blockade of orexin type-1 receptors in locus coeruleus nucleus attenuates the development of morphine dependency in rats

The aim of this study was to evaluate the effects of orexin type-1 receptor (OX1R) antagonism in locus coeruleus (LC) nucleus on the development of morphine physical dependence in rats. Animals were rendered dependent on morphine by subcutaneous (s.c.) administration of morphine sulfate (6, 16, 26, 36, 46, 56 and 66mg/kg, 2ml/kg) at set intervals of 24h for 7 days. Immediately before each morphine administration, the animals received intra-LC administration of SB-334867 (3mM, 0.2μl), a selective orexin type-1 receptor antagonist. On day 8, naloxone (3mg/kg, i.p.) was injected and physical dependence was evaluated for 30min. Our results showed that administration of OX1R antagonist before each morphine injection significantly decreased somatic signs of naloxone-induced morphine withdrawal syndrome, including defecation, wet-dog shake, diarrhea, jumping, scratching, and teeth chattering. These results suggest that the activation of OX1R in LC nucleus might be involved in the development of morphine dependency.

Evaluation of the neuroprotective activity of stansin 6, a resin glycoside from Ipomoea stans

Stansin 6 a tetrasaccharide resin glycoside isolated from the root of Ipomoea stans was evaluated as anticonvulsant and neuroprotective in kainic acid-induced seizures of rats. Intraperitoneal injection of kainic acid (10mg/kg) induced typical behavioral seizures such as wet dog shakes and limbic seizures, and histopathological changes in the hippocampus (degeneration and loss of pyramidal cells in CA1 to CA4 areas). Stansin 6 (10–80mg/kg) had no effect on the behavior of rats and did not induce hippocampal damage. Pretreatment with stansin 6 inhibited convulsions in rats from kainic acid-induced seizures, reduced the degeneration pattern in the CA3 region, decreased astrocytic reactivity, and reduced the expression of IL-1β and TNF-α induced by kainic acid. These results suggest that stansin 6 possesses neuroprotective and anticonvulsant activities.

Neuropeptide trefoil factor 3 attenuates naloxone-precipitated withdrawal in morphine-dependent mice.

The persistence of physical dependence and craving in addicts is considered to contribute to relapse. Increasing evidence indicates that neuropeptide systems are associated with several phases of drug addiction, but little is known about whether the neuropeptide trefoil factor affects withdrawal symptoms. This study aims to investigate the potential effects of the neuropeptide trefoil factor 3 (TFF3) on naloxone-precipitated withdrawal symptoms in morphine-dependent mice. Mice received increasing doses of morphine over 3days. On day 4, the mice were injected with TFF3 (1.0mg/kg, i.p.) 30min after the last dose of morphine. Thirty minutes after TFF3 treatment, naloxone (1mg/kg, i.p.) was injected, and body weight, jumping behavior, wet-dog shakes, and locomotor activity were assessed 30min later. Naloxone caused significant weight loss and increased jumping behavior and wet-dog shakes in morphine-dependent mice. TFF3 (1.0mg/kg) reversed these behavioral symptoms caused by morphine withdrawal, suggesting that TFF3 might ameliorate physical dependence associated with opiate addiction. Furthermore, TFF3 pretreatment significantly reduced morphine withdrawal-induced increases in plasma corticosterone and adrenocorticotropic hormone levels. The glucocorticoid receptor agonist RU486 blocked the behavioral effects of TFF3 on morphine withdrawal symptoms. Finally, Fos expression in the medial prefrontal cortex which was decreased during morphine withdrawal was increased by TFF3 pretreatment. These findings indicate that TFF3 might be a potential therapeutic candidate for opiate addiction by regulating glucocorticoid secretion and neuronal activation in the prefrontal cortex.

Hyperbaric oxygen treatment suppresses withdrawal signs in opioid‐dependent mice (659.12)

HBO2 therapy has been approved by the Food and Drug Administration for limited clinical conditions (Gesell, The Hyperbaric Oxygen Therapy Committee Report: Indications and Results, 12th Ed, 2008). It has been reported that HBO2 treatments reduce opioid withdrawal in human subjects (Epifanova, Anesteziol Reanimatol, May‐June 1995 issue, 34‐39). However, no further research has been conducted to investigate the mechanism of HBO2 in reducing opioid withdrawal. The purpose of this research was to determine whether HBO2 treatment could suppress signs of withdrawal in opioid‐dependent mice. Male NIH Swiss mice received repeated s.c. injections of morphine sulfate or saline twice a day for 4 days. The daily dose of morphine sulfate was increased progressively from 50 mg/kg on day 1 to 125 mg/kg on day 4. On day 5, opioid withdrawal was precipitated by intraperitoneal injection of 5.0 mg/kg naloxone. Withdrawal signs in mice, including jumping, forepaw tremor and wet dog shakes, were recorded for 30 min and scored. Sixty min prior to the naloxone injection, different groups of mice received a 30‐min or 60‐min HBO2 treatment at 3.5 atmospheres absolute. The results show that HBO2 treatment caused a dose‐dependent reduction in withdrawal jumping, forepaw tremor and wet dog shakes in opioid‐dependent mice.Grant Funding Source: Supported by NIH Grant AT‐007222 and the Allen I. White Distinguished Professorship.

Optimization of Potency and Pharmacokinetic Properties of Tetrahydroisoquinoline Transient Receptor Potential Melastatin 8 (TRPM8) Antagonists

Transient receptor potential melastatin 8 (TRPM8) is a nonselective cation channel expressed in a subpopulation of sensory neurons in the peripheral nervous system. TRPM8 is the predominant mammalian cold temperature thermosensor and is activated by cold temperatures ranging from 8 to 25 °C and cooling compounds such as menthol or icilin. TRPM8 antagonists are being pursued as potential therapeutics for treatment of pain and bladder disorders. This manuscript outlines new developments in the SAR of a lead series of 1,2,3,4-tetrahydroisoquinoline derivatives with emphasis on strategies to improve pharmacokinetic properties and potency. Selected compounds were profiled in two TRPM8 target-specific in vivo coverage models in rats (the icilin-induced wet dog shake model and the cold pressor test). Compound 45 demonstrated robust efficacy in both pharmacodynamic models with ED90 values <3 mg/kg.

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), NG-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.

Spontaneous seizures in a rat models of multiple prenatal lesioning

Focal cortical dysplasia (FCD) is an important cause of intractable epilepsy. Previous rat studies have utilized freeze lesioning of neonatal animals to model FCD; however, such models are unable to demonstrate spontaneous seizures without seizure-provoking events. Therefore, we created an animal model with multiple FCD, produced during embryonic development, and observed whether spontaneous seizures occurred. Furthermore, we examined the relationship between FCD and epileptogenesis using immunohistochemistry. At 18 days postconception, a frozen metal probe was placed bilaterally on the scalps of Sprague-Dawley rat embryos through the uterus wall to produce multiple FCD. Eleven of 16 rats showed spontaneous seizures arising in the hippocampus from postnatal day47. Movement cessation followed by sniffing and mastication, culminating in wet-dog shaking, was seen during the hippocampal EEG discharges. Alterations in the levels of glutamatergic and GABA-ergic receptors were investigated during growth. We created an animal model showing spontaneous seizures without a provoking event except for the existence of cortical dysplasia, and without a genetic or general systematic cause like MAM injection or irradiation. The seizures resembled human temporal lobe epilepsy both clinically and on EEG. This model should enable better clarification of the mechanisms underlying the development of human epilepsy.

Duloxetine Attenuated Morphine Withdrawal Syndrome in the Rat

Long term exposure to morphine can induce dependence. The exact mechanisms of dependence are not yet fully understood. Many studies have been conducted to find new drugs that can prevent dependence. This study examined the effects of the chronic administration of duloxetine on the morphine withdrawal syndrome in rats. To this end, male Wistar rats (170-220 g) were randomly divided into 5 groups including one saline treated group (non-depend­ent group) and 4 morphine dependent groups. The experimental groups received additive doses of morphine for 9 days in order to induce dependence according to the following protocol: day 1:5 mg/kg/12 h, days 2 and 3: 10 mg/kg/12 h, days 4, 5:15 mg/kg/12 h, days 6 and 7: 20 mg/kg/12 h and days 8 and 9: 25 mg/kg/12 h. On the ninth day, the morning dose of morphine was only injected. It is worth noting that 30 min before the morning dose of morphine, duloxetine (10, 20, and 40 mg/kg) was injected intraperitoneally. In addition, 2 h after the last injection of morphine, the morphine withdrawal was precipitated by naloxone. The withdrawal signs were recorded for 30 min; these signs included jumping, rearing, genital grooming, abdominal writhing, wet dog shaking, and teeth grinding. The results of the study revealed that the chronic administration of duloxetine decreased all the withdrawal signs. Besides, it attenuated the total withdrawal scores significantly. Results indicate that the regulatory effects on serotonergic and noradrenergic parameters might be associated with the amelioration of the withdrawal symptoms.

Both prolactin (PRL) and a molecular mimic of phosphorylated PRL, S179D-PRL, protect the hippocampus of female rats against excitotoxicity

Prolactin (PRL) has many functions in the CNS, including neuroprotection. During lactation, the dorsal hippocampus is protected from excitotoxic kainic acid (KA)-induced cellular damage. We have previously reported that systemic pre-treatment with ovine PRL had similar protective effects in female rats. Here, we asked (1) whether intracerebral human PRL (hPRL) would have the same action, (2) because phosphorylated PRL is high in lactation, whether a mimic of phosphorylated hPRL, human prolactin in which the normally phosphorylated serine at position 179 is replaced with an aspartate (S179D-PRL), had similar activity, and (3) what signaling pathways mediated the protective effect. Female ovariectomized (OVX, 1month) rats were implanted with micro-osmotic pumps connected to unilateral icv cannulae directed at the right lateral ventricle. The pumps delivered 0.10ng/h of hPRL, S179D-PRL, a combination of hPRL+S179D-PRL, or saline vehicle for 7days prior to a systemic dose of 7.5mg/kg of KA. Rats were sacrificed 48h after KA injection. Immunostaining for neuronal nuclei (Neu-N) revealed a significant KA-induced decrease in cell number in the CA1, CA3, and CA4 hippocampal areas of rats (∼55% of control). Treatment with either hPRL or S179D-PRL or the combination prevented the damaging effect of KA in these hippocampal regions (∼95% of corresponding control), but was not completely effective at preventing early seizure-related behaviors such as staring and wet dog shakes. Analysis of signals generated by hPRL and S179D-PRL showed no activation of signal transducer and activation of transcription 5 (Stat5) or other signaling molecules in the hippocampus, but activation of extracellular-regulated kinase (ERK)1/2 in the amygdala. These results support a central protective effect of both PRL forms and suggest that PRL could be exerting its protective action by indirectly modulating input signals to the hippocampus and thus regulating excitability.

Effect of prenatal methamphetamine exposure and challenge dose of the same drug in adulthood on epileptiform activity induced by electrical stimulation in female rats

Our previous study demonstrated that chronic prenatal methamphetamine (MA) exposure and a single dose of MA in adulthood decrease focally induced epileptiform activity in adult male rats. As seizures are known to be dependent on sex and female estrous cycle, the goal of the present study was to examine the combined effect of prenatal MA exposure (5mg/kg) and the MA challenge dose (1mg/kg) in adulthood on electroencephalography (EEG) recordings and consequences of brain stimulation in freely moving adult female rats with respect to the estrous cycle. Overall, 12 groups of adult female rats were tested: prenatally MA-exposed, prenatally saline-exposed and rats without prenatal injections, each of these groups was either postnatally challenged with MA or with saline injection (MA–MA, MA–S; S–MA, S–S; C–MA, C–S) and further divided according to the stage of the estrous cycle to metestrus/diestrus (M/D) or proestrus/estrus (P/E). Seizures were induced by repetitive electrical stimulation (15s/8Hz) of sensorimotor cortex. Stimulation threshold, duration of afterdischarges (ADs), and presence and duration of spontaneous ADs (SADs) were evaluated. Additionally, behavior associated with stimulation and ADs, and occurrence of wet-dog-shakes (WDS) were analyzed. The present study demonstrates that the prenatal MA exposure decreased the seizure threshold in females in M/D, but not in females in P/E. In addition, prenatally MA-exposed M/D females injected with saline in adulthood had increased the duration of ADs as well as SADs. The challenge dose of MA also decreased the seizure threshold. Moreover, prenatal as well as adult MA administration decreased the number and occurrence of WDS, respectively. Thus, the present study demonstrates that the effect of prenatal MA exposure and challenge dose of the same drug on focally induced epileptiform activity in adult female rats depends on the estrous cycle.

Gap junction blockers: a potential approach to attenuate morphine withdrawal symptoms

BackgroundThe exact mechanisms of morphine-induced dependence and withdrawal symptoms remain unclear. In order to identify an agent that can prevent withdrawal syndrome, many studies have been performed. This study was aimed to evaluate the effect of gap junction blockers; carbenoxolone (CBX) or mefloquine (MFQ); on morphine withdrawal symptoms in male rat.Adult male Wistar rats (225 – 275 g) were selected randomly and divided into 10 groups. All groups underwent stereotaxic surgery and in order to induce dependency, morphine was administered subcutaneously) Sc) at an interval of 12 hours for nine continuous days. On the ninth day of the experiment, animals received vehicle or CBX (100, 400, 600 μg/10 μl/rat, icv) or MFQ (50, 100 and 200 μg/10 μl/rat, icv) after the last saline or morphine (Sc) injection. Morphine withdrawal symptoms were precipitated by naloxone hydrochloride 10 min after the treatments. The withdrawal signs including: jumping, rearing, genital grooming, abdomen writhing, wet dog shake and stool weight, were recorded for 60 minutes.ResultsResults showed that CBX and MFQ decreased all withdrawal signs; and the analysis indicated that they could attenuate the total withdrawal scores significantly.ConclusionTaking together it is concluded that gap junction blockers prevented naloxone-precipitated withdrawal symptoms.

Opiate exposure and withdrawal dynamically regulate mRNA expression in the serotonergic dorsal raphe nucleus

Previous results from our lab suggest that hypofunctioning of the serotonergic (5-HT) dorsal raphe nucleus (DRN) is involved in stress-induced opiate reinstatement. To further investigate the effects of morphine dependence and withdrawal on the 5-HT DRN system, we measured gene expression at the level of mRNA in the DRN during a model of morphine dependence, withdrawal and post withdrawal stress exposure in rats. Morphine pellets were implanted for 72h and then either removed or animals were injected with naloxone to produce spontaneous or precipitated withdrawal, respectively. Animals exposed to these conditions exhibited withdrawal symptoms including weight loss, wet dog shakes and jumping behavior. Gene expression for brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), corticotrophin releasing-factor (CRF)-R1, CRF-R2, alpha 1 subunit of the GABAA receptor (GABAA-α1), μ-opioid receptor (MOR), 5-HT1A receptor, tryptophan hydroxylase2 (TPH2) and the 5-HT transporter was then measured using quantitative real-time polymerase chain reaction at multiple time-points across the model of morphine exposure, withdrawal and post withdrawal stress. Expression levels of BDNF, TrkB and CRF-R1 mRNA were decreased during both morphine exposure and following 7days of withdrawal. CRF-R2 mRNA expression was elevated after 7days of withdrawal. 5-HT1A receptor mRNA expression was decreased following 3h of morphine exposure, while TPH2 mRNA expression was decreased after 7days of withdrawal with swim stress. There were no changes in the expression of GABAA-α1, MOR or 5-HT transporter mRNA. Collectively these results suggest that alterations in neurotrophin support, CRF-dependent stress signaling, 5-HT synthesis and release may underlie 5-HT DRN hypofunction that can potentially lead to stress-induced opiate relapse.

Effects of rutin on oxidative stress in mice with kainic acid-induced seizure

Flavonoids are present in foods such as fruits and vegetables. Several studies have demonstrated a relationship between the consumption of flavonoid-rich foods and prevention of human disease, including neurodegenerative disorders. We assessed the effect of rutin (quercetin-3-O-rutinoside) on oxidative stress in kainic acid (KA)-induced seizure. Thirty-six BALB/c mice were randomly divided into three groups. In the control group, saline (intra-peritoneal, i.p.) was administered for 7 d, and on the last day, KA (10 mg/kg, i.p.) was injected 30 min after administration of saline. In rutin groups, mice were pretreated with rutin (100 and 200 mg/kg, i.p.) for 7 d, and on the last day, KA (10 mg/kg, i.p.) was injected 30 min after administration of rutin. Subsequently, behavioural changes were observed in mice. Lipid peroxidation and oxidative stress were measured respectively in the early and late phases after KA-induced seizures. Seizure scores in the rutin groups were significantly lower than those in the control group (P < 0.01). Furthermore, rutin dose-dependently inhibited the number of wet-dog shakes (WDS) (P < 0.05). Malondialdehyde level in the hippocampus of the rutin groups was significantly lower than that in the hippocampus of the control group on days 1 and 21 after KA administration. In the rutin groups, the thiol levels observed on day 1 after KA administration were higher than that in the control group (P < 0.01). These results indicate that rutin has potential anticonvulsant and antioxidative activities against oxidative stress in KA-induced seizure in mice.

Spontaneous seizures in a rat model of multiple prenatal freeze lesioning

Focal cortical dysplasia (FCD) is an important cause of intractable epilepsy. Previous rat studies have utilized freeze lesioning of neonatal animals to model FCD; however, such models are unable to demonstrate spontaneous seizures without seizure-provoking events. Therefore, we created an animal model with multiple FCD, produced during embryonic development, and observed whether spontaneous seizures occurred. Furthermore, we examined the relationship between FCD and epileptogenesis using immunohistochemistry. At 18 days postconception, a frozen metal probe was placed bilaterally on the scalps of Sprague-Dawley rat embryos through the uterus wall to produce multiple FCD. Electroencephalogram (EEG) and video recording were performed from postnatal day (P) 35 to P77. Brain tissues were examined immunohistochemically at P28 and P78 using semiquantitative densitometry. Eleven of 16 rats (68.8%) showed spontaneous seizures arising in the hippocampus from P47. Movement cessation followed by sniffing and mastication, culminating in wet-dog shaking, was seen during the hippocampal EEG discharges. FCD was observed in the bilateral frontoparietal lobes. The expression levels of N-methyl-d-aspartate receptor (NMDAR) subunits 1, 2A, 2B, the glutamate/aspartate transporter and the glial glutamate transporter 1 (GLT1) at FCD sites were increased at P28 and P78. There were no major histological abnormalities in the hippocampi compared with those in the cortex. However, the expression levels of NMDAR 2A and 2B were increased at P28. Levels of NMDAR1, 2A and 2B, the glutamate/aspartate transporter and GLT1 were also increased at P78. We created an animal model showing spontaneous seizures without a provoking event except for the existence of cortical dysplasia, and without a genetic or general systematic cause like MAM injection or irradiation. The seizures resembled human temporal lobe epilepsy both clinically and on EEG. Alterations in the levels of glutamatergic and GABAergic receptors were investigated during growth. This model should enable better clarification of the mechanisms underlying the development of human epilepsy.

Mifepristone Pretreatment Reduces Ethanol Withdrawal Severity In Vivo

Prolonged ethanol (EtOH) intake may perturb function of the hypothalamic-pituitary-adrenal axis in a manner that promotes dependence and influences EtOH withdrawal severity. Prior in vivo and in vitro studies suggest that corticosteroids, in particular, may be elevated during EtOH intoxication and withdrawal, suggesting that intracellular glucocorticoid receptors (GRs) may promote the development of EtOH dependence. Adult male Sprague-Dawley rats were subjected to a 4-day binge-like EtOH administration regimen (3 to 5 g/kg/i.g. every 8 hours designed to produce peak blood EtOH levels (BELs) of <300 mg/dl). Subgroups of animals received s.c. injection of the GR antagonist mifepristone (20 or 40 mg/kg in peanut oil at 0800 hours on each of the 4 days prior to withdrawal). BELs were assessed at 0900 and 1500 hours on Days 2 (D2) and 4 (D4) of the regimen. BEL, blood corticosterone levels (BCLs), and EtOH withdrawal-associated behavioral abnormalities were assessed 10 to 12 hours after the final EtOH administration. Daily mean EtOH doses for D1 to D4 of the regimen were 14.4, 9.9, 7.1, and 8.6 g/kg, respectively. The EtOH gavage regimen produced mean BELs of 255 mg/dl at 0900 on D2 and 156.2 mg/dl at 0900 on D4 of the regimen. Withdrawal from the EtOH exposure regimen, beginning 10 hours after the last EtOH administration, produced significant elevations in BCL and behavioral abnormalities including tremors, stereotypy, and "wet dog shakes." Mifepristone administration did not alter food intake or weight during the 4-day regimen, nor were there drug-dependent differences in BEL or BCL on withdrawal day. Although mifepristone produced no significant changes in behavior of EtOH-naïve animals, pretreatment with mifepristone (40 mg/kg) significantly reduced the severity of EtOH withdrawal. Findings suggest that activation of GRs promotes neuroadaptation to binge-like EtOH exposure, contributing to the development of EtOH dependence. Further, GRs may represent therapeutic targets to be exploited in reducing the severity of EtOH withdrawal.

Systemic inflammation alters central 5-HT function as determined by pharmacological MRI

Considerable evidence indicates a link between systemic inflammation and central 5-HT function. This study used pharmacological magnetic resonance imaging (phMRI) to study the effects of systemic inflammatory events on central 5-HT function. Changes in blood oxygenation level dependent (BOLD) contrast were detected in selected brain regions of anaesthetised rats in response to intravenous administration of the 5-HT-releasing agent, fenfluramine (10 mg/kg). Further groups of rats were pre-treated with the bacterial lipopolysaccharide (LPS; 0.5 mg/kg), to induce systemic inflammation, or the selective 5-HT2A receptor antagonist MDL100907 prior to fenfluramine. The resultant phMRI data were investigated further through measurements of cortical 5-HT release (microdialysis), and vascular responsivity, as well as a more thorough investigation of the role of the 5-HT2A receptor in sickness behaviour. Fenfluramine evoked a positive BOLD response in the motor cortex (+ 15.9 ± 2%) and a negative BOLD response in the dorsal raphe nucleus (− 9.9 ± 4.2%) and nucleus accumbens (− 7.7 ± 5.3%). In all regions, BOLD responses to fenfluramine were significantly attenuated by pre-treatment with LPS (p < 0.0001), but neurovascular coupling remained intact, and fenfluramine-evoked 5-HT release was not affected. However, increased expression of the 5-HT2A receptor mRNA and decreased 5-HT2A-dependent behaviour (wet-dog shakes) was a feature of the LPS treatment and may underpin the altered phMRI signal. MDL100907 (0.5 mg/kg), 5-HT2A antagonist, significantly reduced the BOLD responses to fenfluramine in all three regions (p < 0.0001) in a similar manner to LPS. Together these results suggest that systemic inflammation decreases brain 5-HT activity as assessed by phMRI. However, these effects do not appear to be mediated by changes in 5-HT release, but are associated with changes in 5-HT2A-receptor-mediated downstream signalling pathways.

Suppressive effects of rosa damascena essential oil on naloxone- precipitated morphine withdrawal signs in male mice.

This research was done to test the effect of Rosa damascena essential oil on withdrawal signs of naloxone-precipitated morphine in male mice. Morphine dependence was induced by injection (IP) three times daily at doses of 50, 50 and 75 mg/kg, respectively, for 3 days. On day 4, after the last administration of morphine, Rosa damascena essential oil was administered at different concentrations (5, 2 and 40%, IP) 30 min before administration of naloxone (5 mg/kg, IP). The following actions were taken as signs of withdrawal and records taken for jumping as a number and scores of 0 to 3 were given for incidences of grooming, teeth chattering, rearing, writing, diarrhea, wet dog shakes and climbing during a 30 min period. Results showed that different concentrations of Rosa damascena essential oil significantly reduced signs of morphine withdrawal compared to the control group in terms of number of jumps (p < 0.05 and p < 0.01), grooming, teeth chattering, rearing, climbing, wet dog shakes and writhing, but not for diarrhea (p < 0.05). In conclusion it seems that GABAergic activity induced by flavonoids from Rosa damascena essential oil can alleviate signs of morphine withdrawal, but further studies need to be done to better understand this mechanism.

Effects of L-Arginine on Seizure Behavior and Expression of GFAP in Kainic Acid-Treated Rats

Rats i.p. injected once with 10 mg/kg kainic acid exhibited clear seizure behavior (“wet-dog shakes,” rearing on the hindlimbs, and bilateral clonus). Pretreatment with L-arginine (L-Arg twice a day for 5 days) significantly decreased these manifestations. The medium dose of L-Arg (40 mg/kg) was found to be close to optimum; 10 and 160 mg/kg L-Arg provided much smaller positive effects. In KA-treated rats, a much higher density of GFAP-positive astrocytes was found in the hilus of the dorsal hippocampus, while 40 mg/kg L-Arg+KA-treated rats demonstrated noticeably weaker GFAP overexpression. The results of Western blotting analysis were fully comparable with those obtained in the immunostaining experiments.

Brain kinin B1 receptor contributes to the onset of stereotypic nocifensive behavior in rat

While brain kinin B1 receptor (B1R) is virtually absent in control rats, it contributes to hypertension via a midbrain dopaminergic (DA) mechanism in spontaneously hypertensive rat (SHR) and Angiotensin II (Ang II)-induced hypertension. This study aims at determining whether B1R can also affect stereotypic nocifensive behavior through DA and/or other neuromediators in the same models. The selective B1R agonist Sar[D-Phe8][des-Arg9]BK was injected i.c.v. (1μg/site) to freely behaving SHR (16 weeks), Ang II-hypertensive rats (200ng/kg/min×2 weeks, s.c.) and control Wistar-Kyoto rats (WKY). Behavioral activity to the agonist was measured before and after treatment with receptor antagonists (10μg/site i.c.v. or otherwise stated) for B1 (SSR240612), tachykinin NK1 (RP67580), glutamate NMDA (DL-AP5), DA D1 (SCH23390, 0.2mg/kg s.c.) and D2 (Raclopride, 0.16mg/kg s.c.). Other studies included inhibitors (10μg/site) of NOS (l-NNA) and iNOS (1400W). The possible desensitisation of B1R upon repeated intracerebral stimulation was also excluded. B1R expression was measured by qRT-PCR in selected areas and by immunohistochemistry in the ventral tegmental area. Results showed that the B1R agonist had no effect in WKY, yet it induced nocifensive behavioral manifestations in both models of hypertension (face washing, sniffing, head scratching, rearing, teeth chattering, grooming, digging, licking, wet-dog shakes). These responses were prevented by all antagonists and inhibitors tested, but 1400W had a less inhibitory effect on most behaviors. Compared with WKY, B1R mRNA levels were markedly enhanced in hypothalamus, ventral tegmental area and nucleus accumbens of SHR and Ang II-treated rats. B1R was detected on DA neuron of the ventral tegmental area in SHR. Data suggest that kinin B1R is upregulated in midbrain DA system in hypertensive rats and its i.c.v. activation induced stereotypic nocifensive behavior that is mediated by several mediators, notably substance P, glutamate, DA and NO.

Temporal lobe epileptiform activity following systemic administration of 4‐aminopyridine in rats

The K(+) channel blocker 4-aminopyridine (4AP) induces epileptiform synchronization in brain slices maintained in vitro without interfering with γ-aminobutyric acid (GABA)A receptor-mediated inhibition and, actually, even enhancing it. The hypothesis that similar electrographic epileptiform patterns occur in vivo following systemic 4AP injection was tested here. Sprague-Dawley rats (n = 13) were implanted with bipolar electrodes aimed at the hippocampal CA3 region, entorhinal cortex, subiculum, dentate gyrus, and amygdala. They were then injected with a single dose of 4AP (4-5 mg/kg, i.p.), and video-monitoring/electroencephalography (EEG) recordings were performed. 4AP induced convulsive or nonconvulsive seizures in 12 of 13 rats, along with generalized fascicular twitching, wet-dog shakes, and myoclonic jerks. On EEG, we observed in 7 (58.3%) of 12 animals long-lasting interictal spikes from the subiculum before the occurrence of the first seizure. Once seizures had started, interictal spikes occurred in all areas with no fixed site of origin. Most seizures (41/60, 68.3%) were characterized by a low-voltage fast-activity onset pattern and were convulsive (48/60, 80%). 4AP also induced highly rhythmic theta (6-11 Hz) oscillations in CA3 and entorhinal cortex before seizure occurrence. Our study shows that systemic 4AP administration in vivo can enhance theta oscillations and induce slow interictal spikes and low-voltage fast-onset seizures similar to those reported in brain slices. We propose that these effects may reflect, at least in part, enhanced GABAA receptor-mediated inhibition as reported in in vitro studies.