The effect of L-arginine and L-NAME on pentylenetetrazole induced seizures in ovariectomized rats, an in vivo study

Arginine Reduces Glycation in γ2 Subunit of AMPK and Pathologies in Alzheimer's Disease Model Mice

The metabolism disorders are a common convergence of Alzheimer's disease (AD) and type 2 diabetes mellitus (T2DM). The characteristics of AD are senile plaques and neurofibrillary tangles (NFTs) composed by deposits of amyloid-β (Aβ) and phosphorylated tau, respectively. Advanced glycation end-products (AGEs) are a stable modification of proteins by non-enzymatic reactions, which could result in the protein dysfunction. AGEs are associated with some disease developments, such as diabetes mellitus and AD, but the effects of the glycated γ2 subunit of AMPK on its activity and the roles in AD onset are unknown.

METHODS

We studied the effect of glycated γ2 subunit of AMPK on its activity in N2a cells. In 3 × Tg mice, we administrated L-arginine once every two days for 45 days and evaluated the glycation level of γ2 subunit and function of AMPK and alternation of pathologies.

RESULTS

The glycation level of γ2 subunit was significantly elevated in 3 × Tg mice as compared with control mice, meanwhile, the level of pT172-AMPK was obviously lower in 3 × Tg mice than that in control mice. Moreover, we found that arginine protects the γ2 subunit of AMPK from glycation, preserves AMPK function, and improves pathologies and cognitive deficits in 3 × Tg mice.

CONCLUSIONS

Arginine treatment decreases glycated γ2 subunit of AMPK and increases p-AMPK levels in 3 × Tg mice, suggesting that reduced glycation of the γ2 subunit could ameliorate AMPK function and become a new target for AD therapy in the future.

Transcranial photobiomodulation add-on therapy to valproic acid for pentylenetetrazole-induced seizures in peripubertal rats

Background

Convulsive status epilepticus (CSE) prevention is critical for pediatric patients with epilepsy. Immediate intervention before CSE reduce severity. Despite its wide usage as an anticonvulsant, valproic acid (VPA) results in harmful side effects such as dose-dependent hepatotoxicity. Hence, reducing VPA dosage to minimize side effects while maintaining its efficacy is necessary, and transcranial photobiomodulation (tPBM) add-on therapy could facilitate this. We recently demonstrated for the first time that tPBM at a wavelength of 808 nm attenuated CSE in peripubertal rats. However, the effects of VPA with the add-on therapy of tPBM prior to seizures have not yet been explored. This study investigated whether adding tPBM to VPA exerts synergistic effect for CSE prevention in peripubertal rats.

Methods

A gallium-aluminum-arsenide laser (wavelength of 808 nm with an exposure duration of 100 s and irradiance of 1.333 W/cm² at the target) was applied transcranially 30 min after VPA injection in Sprague Dawley rats. All the rats received 90 mg/kg of pentylenetetrazole (PTZ). Except for the saline (n = 3), tPBM + saline (n = 3), and PTZ group (n = 6), all the rats received a PTZ injection 30 min after VPA injection. The rats received add-on tPBM with PTZ immediately after tPBM. In the VPA + PTZ group, the rats received low-dose (100 mg/kg, n = 6), medium-dose (200 mg/kg, n = 6), and high-dose (400 mg/kg, n = 7) VPA. In the VPA + tPBM + PTZ group, the rats received low (100 mg/kg, n = 5), medium (200 mg/kg, n = 6), and high (400 mg/kg, n = 3) doses of VPA. Seizures were evaluated according to the revised Racine’s scale in a non-blinded manner.

Results

Adding tPBM to low-dose VPA reduced the incidence of severe status epilepticus and significantly delayed the latency to stage 2 seizures. However, adding tPBM to high-dose VPA increased the maximum seizure stage, prolonged the duration of stage 4–7 seizures, and shortened the latency to stage 6 seizures.

Conclusions

Adding tPBM to low-dose VPA exerted a synergistic prevention effect on PTZ-induced seizures, whereas adding tPBM to high-dose VPA offset the attenuation effect.

Neuroprotective effects of Pinus eldarica in a mouse model of pentylenetetrazole-induced seizures

Objective:

Oxidative stress has pernicious effects on the brain. Pinus eldarica has antioxidant properties. We explored neuroprotective effect of P. eldarica against pentylenetetrazole (PTZ)-induced seizures.

Materials and Methods:

Male mice (BALB/c) were grouped as control, PTZ, Soxhlet (Sox) 100, Sox 200, Macerated (Mac) 100 and Mac 200 groups. Sox and Mac extracts (100 and 200 mg/kg) were injected during 7 days. Delay in onset of minimal clonic seizure (MCS) and generalized tonic- clonic seizure (GTCS) was measured. Number of dark neurons (DN) and levels of oxidative stress indicators in the hippocampus were evaluated.

Results:

Onset of MCS and GTCS was later in groups treated with the extracts than the PTZ group (p<0.01 and p<0.001). Number of DN in the hippocampus in the PTZ group was higher than the control group (p<0.001) while in the extract groups, was lower than the PTZ group (p<0.05, p<0.01 and p<0.001). MDA level was higher whereas total thiol level and activity of SOD and CAT were lower (p<0.001) in the PTZ group than the control group. MDA level in the Sox 100 (p<0.01), Sox 200 (p<0.001) and Mac 200 (p<0.01) groups was less than the PTZ group. Total thiol level in the Sox 200 (p<0.001), SOD in the Sox 100 (p<0.05), Sox 200, and Mac 200 and CAT in the Sox 200 (p<0.001) groups were higher than the PTZ group.

Conclusion:

P. eldarica prevented neuronal death and reduced seizures caused by PTZ via improving brain oxidative stress.

The effects of soy on scopolamine-induced spatial learning and memory impairments are comparable to the effects of estradiol

Background Modulatory effects of soy extract and estradiol on the central nervous system (CNS) have been reported. The effect of soy on scopolamine-induced spatial learning and memory in comparison to the effect of estradiol was investigated. Materials and methods Ovariectomized rats were divided into the following groups: (1) control, (2) scopolamine (Sco), (3) scopolamine-soy 20 (Sco-S 20), (4) scopolamine-soy 60 (Sco-S 60), (5) scopolamine-estradiol 20 (Sco-E 20) and (6) scopolamine-estradiol 60 (Sco-E 60). Soy extract, estradiol and vehicle were administered daily for 6 weeks before training in the Morris water maze (MWM) test. Scopolamine (2 mg/kg) was injected 30 min before training in the MWM test. Results In the MWM, the escape latency and traveled path to find the platform in the Sco group was prolonged compared to the control group (p < 0.001). Treatment by higher doses of soy improved performances of the rats in the MWM (p < 0.05 - p < 0.001). However, treatment with both doses of estradiol (20 and 60 μg/kg) resulted in a statistically significant improvement in the MWM (p < 0.01 - p < 0.001). Cortical, hippocampal and serum levels of malondialdehyde (MDA), as an index of lipid peroxidation, were increased which was prevented by soy extract and estradiol (p < 0.001). Cortical, hippocampal as well as serum levels of the total thiol, superoxide dismutase (SOD) and catalase (CAT) in Sco group were lower than the control group (p < 0.001) while they were enhanced when the animals were treated by soy extract and estradiol (p < 0.01 - p < 0.001). Conclusions It was observed that both soy extract and estradiol prevented learning and memory impairments induced by scopolamine in ovariectomized rats. These effects can be attributed to their protective effects on oxidative damage of the brain tissue.

Edaravone acts as a potential therapeutic drug against pentylenetetrazole-induced epilepsy in male albino rats by downregulating cyclooxygenase-II

INTRODUCTION

The effects of edaravone against pentylenetetrazole (PTZ)-induced epilepsy in male albino rats were investigated. Edaravone is a well-known commercial drug used in the treatment of strokes and amyotrophic lateral sclerosis (ALS). Antioxidant and free radical scavenging activities of edaravone have been reported in patients with ALS.

METHODS

In this study, the experimental groups were as follows: sham, control, 5 mg/kg edaravone, and 10 mg/kg edaravone. Behavioral assessment, determination of biochemical markers, apoptosis, nitric oxide (NO), and mRNA and protein expression of cyclooxygenase-II (COX-II) were carried out. Seizure incidence, including generalized tonic-clonic seizure (GTCS) and minimal clonic seizure (MCS), was directly associated with PTZ administration in rats.

RESULTS

Edaravone supplementation substantially increased MCS and GTCS latency in rats, and biochemical markers were significantly altered in the brain tissue of PTZ-treated rats. Edaravone treatment normalized altered biochemical markers compared with the untreated control. Apoptosis and NO levels were significantly reduced by more than 50% compared to their respective controls. COX-II mRNA was increased by 130% in PTZ-treated rats, while edaravone supplementation reduced mRNA and protein expression of COX-II by more than 20% and 40%, respectively. Immunohistochemistry indicated that COX-II protein expression was reduced by 13.2% and 33.7% following supplementation with 5 and 10 mg/kg edaravone, respectively.

CONCLUSION

Taken together, our results suggest that edaravone functions by downregulating the levels of COX-II and NO and is a potential candidate for the treatment of PTZ-induced epilepsy.

l-Homocarnosine, l-carnosine, and anserine attenuate brain oxidative damage in a pentylenetetrazole-induced epilepsy model of ovariectomized rats

In this study, we investigated the protective effect of l-homocarnosine, l-carnosine, and anserine (HCA) on seizure-induced brain injuries. We evaluated the protective effect of HCA on brain oxidative damage in a pentylenetetrazole (PTZ)-induced epilepsy model using ovariectomized (OVX) rats. The experimental groups were as follows: group I, sham; group II, sham + PTZ; group III, sham + HCA + PTZ; group IV, OVX; group V, OVZ + PTZ; and group VI, OVX + HCA + PTZ. We determined the levels of lipid peroxidation, glutathione peroxidase (Gpx), reduced glutathione (GSH), catalase, superoxide dismutase (SOD), and thiol in brain hippocampal and cortical tissue. The biochemical markers were significantly altered in the brain tissue of OVX rats. HCA supplementation significantly reduced lipid peroxidation and increased GSH, Gpx, SOD, catalase, and thiol levels in PTZ-treated OVX rats. Rats with an ovariectomy showed a significant protective effect against PTZ through elevation of the latency of generalized tonic-clonic seizures (GTCS). HCA substantially increased minimal clonic seizure and GTCS latency in the OVX-PTZ and sham-PTZ groups. In summary, our experimental data indicate that combined supplementation of HCA substantially increased anticonvulsant activity. Moreover, combined HCA supplementation reduced oxidative damage by decreasing lipid peroxidation and increasing antioxidant levels in the brain of a PTZ-induced seizure rodent model.

The effects of soy and tamoxifen on apoptosis in the hippocampus and dentate gyrus in a pentylenetetrazole-induced seizure model of ovariectomized rats

The effects of tamoxifen and soy on apoptosis of the hippocampus and dentate gyrus of ovariectomized rats after repeated seizures were investigated. Female rats were divided into: (1) Control, (2) Sham, (3) Sham-Tamoxifen (Sham-T), (4) Ovariectomized (OVX), (5) OVX-Tamoxifen (OVX-T), (6)OVX-Soy(OVX-S) and (7) OVX-S-T. The animals in the OVX-S, OVX-T and OVX-S-T groups received soy extract (60 mg/kg; i.p.), tamoxifen (10 mg/kg) or both for 2 weeks before induction of seizures. The animals in these groups additionally received the mentioned treatments before each injection of pentylenetetrazole (PTZ; 40 mg/kg) for 6 days. The animals in the Sham and OVX groups received a vehicle of tamoxifen and soy. A significant decrease in the seizure score and TUNEL-positive neurons was seen in the OVX group compared to the Sham (P < 0.001). The animals in both the OVX-T and OVX-S groups had a significantly higher seizure score as well as number of TUNEL-positive neurons compared to the OVX group (P < 0.01-P < 0.001). Co-treatment of the OVX rats by the extract and tamoxifen decreased the seizure score and number of TUNEL-positive neurons compared to OVX-S (P < 0.001). Treatment of the OVX rats by either soy or tamoxifen increased the seizure score as well as the number of TUNEL-positive neurons in the hippocampal formation. Co-administration of tamoxifen and soy extract inhibited the effects of the soy extract and tamoxifen when they were administered alone. It might be suggested that both soy and tamoxifen have agonistic effects on estrogen receptors by changing the seizure severity.

Effects of genistein on pentylenetetrazole-induced behavioral and neurochemical deficits in ovariectomized rats

Estrogenic compounds have been documented in literature to exert neuroprotective effects. This study investigated the potential neuroprotective effect of genistein; a phytoestrogen at doses of 5, 10, 20, and 40 mg/kg p.o. in ovariectomized rats challenged with pentylenetetrazole (PTZ) 90 mg/kg i.p. Systemic acute administration of PTZ induced seizures, increased oxidative stress, and caused apoptosis and histological abnormalities. Pretreatment with genistein delayed seizure onset, reduced the seizure duration, improved oxidative stress profile, decreased estrogen receptor expression, reduced apoptosis, and improved the histopathological pattern. Overall, the genistein doses (10 and 20 mg/kg) showed the strongest protective effects. In conclusion, the current study suggests that genistein exhibits neuroprotective effects against PTZ-induced seizures. Such effects might be attributed to its estrogenic, antioxidant, and/or anti-apoptotic properties.

Protection against brain tissues oxidative damage as a possible mechanism for improving effects of low doses of estradiol on scopolamine-induced learning and memory impairments in ovariectomized rats

Background:

Regarding the anti-oxidative effects on the central nervous system, the possible protection against brain tissues oxidative damage as a possible mechanism for improving effects of low doses of estradiol on scopolamine-induced learning and memory impairments was investigated in ovariectomized (OVX) rats.

Materials and Methods:

The OVX rats treated by (1) vehicle, (2) scopolamine, and (3–4) scopolamine plus estradiol (20 or 20 or 60 μg/kg). Estradiol was administered (20 or 60 μg/kg, intraperitoneally) daily for 6 weeks after ovariectomy. The rats were examined for learning and memory using passive avoidance test. Scopolamine (2 mg/kg) was injected 30 min after training in the test. The brains were then removed to determine malondialdehyde (MDA) and thiol contents.

Results:

Scopolamine shortened the time latency to enter the dark compartment in (P < 0.01). Compared to scopolamine, pretreatment by both doses of estradiol prolonged the latency to enter the dark compartment (P < 0.01). The brain tissues MDA concentration as an index of lipid peroxidation was decreased (P < 0.05). Pretreatment by estradiol lowered the concentration of MDA, while it increased thiol content compared to scopolamine (P < 0.05 and P < 0.01).

Conclusions:

These results allow us to suggest a protection against brain tissues oxidative damage as a possible mechanism for improving effects of low doses of estradiol on scopolamine-induced learning and memory impairments in OVX rats.

The effects of tamoxifen on spatial and nonspatial learning and memory impairments induced by scopolamine and the brain tissues oxidative damage in ovariectomized rats

Background:

Modulatory effects of tamoxifen (TAM) on the central nervous system have been reported. The effects of TAM on spatial and nonspatial learning and memory impairments induced by scopolamine and the brain tissues oxidative damage was investigated.

Materials and Methods:

The ovariectomized (OVX) rats were divided and treated: (1) Control (saline), (2) scopolamine (Sco; 2 mg/kg, 30 min before behavioral tests), (3–5) Sco-TAM 1, Sco-TAM 3 and Sco-TAM 10. TAM (1, 3 or 10 mg/kg; i.p.) was daily administered for 6 weeks.

Results:

In Morris water maze (MWM), both the latency and traveled distance in the Sco-group were higher than control (P < 0.001) while, in the Sco-TAM 10 group it was lower than Sco-group (P < 0.05). In passive avoidance test, the latency to enter the dark compartment was higher than control (P < 0.05 – P < 0.01). Pretreatment by all three doses of TAM prolonged the latency to enter the dark compartment compared to Sco-group (P < 0.05 – P < 0.001). The brain tissues malondialdehyde (MDA) concentration was increased while, superoxide dismutase activity (SOD) decreased in the Sco-group compared to control (P < 0.05 – P < 0.01). Pretreatment by TAM lowered the concentration of MDA while, increased SOD compared to Sco-group (P < 0.05 – P < 0.001).

Conclusions:

It is suggested that TAM prevents spatial and nonspatial learning and memory impairments induced by scopolamine in OVX rats. The possible mechanism(s) might at least in part be due to protection against the brain tissues oxidative damage.

The effects of tamoxifen on learning, memory and brain tissues oxidative damage in ovariectomized and naïve female rats

Background:

Regarding the modulatory effects of tamoxifen (TAM) on the actions of estrogen in the present study, the effects of TAM on learning, memory and brain tissues oxidative damage in ovariectomized (OVX) and naοve female rats was investigated.

Materials and Methods:

The animals were divided into: (1) Sham, (2) OVX, (3) Sham-tamoxifen (Sham-TAM) and (4) ovariectomized-tamoxifen (OVX-TAM). The animals of the Sham-TAM and OVX-TAM groups were treated by TAM (1 mg/kg; 4 weeks).

Results:

In Morris water maze, the escape latency in the OVX group was higher than in the Sham group (P < 0.01). The time latency in the animals of OVX-TAM group was lower than that of OVX group (P < 0.01); however, there were no significant differences between the Sham-TAM and Sham groups. In the probe trial, the time spent in target quadrant (Q₁) by the animals of OVX group was lower than that of Sham group (P < 0.01). Interestingly, the animals of OVX-TAM group spent more times in target quadrant (Q₁) compared with OVX group (P < 0.01). In passive avoidance test, the animals of OVX group had lower latencies to enter the dark compartment compared with the Sham group (P < 0.05). The time latency to enter the dark compartment by animals of OVX-TAM group was higher than in OVX group (P < 0.01). In OVX-TAM group, the total thiol concentration was significantly higher (P < 0.05) and malondialdehyde concentration was lower (P < 0.01) than OVX group.

Conclusions:

These results allow us to propose that TAM enhances learning and memory of OVX rats. The possible mechanism may be due to the protective effects against brain tissues oxidative damage.

Protective role of endogenous ovarian hormones against learning and memory impairments and brain tissues oxidative damage induced by lipopolysaccharide

BACKGROUND

The contribution of neuroinflammation in Alzheimer's disease (AD) has been widely reported. The effects of female gonadal hormones in both neuroinflammation and brain cognitive functions have also been well considered.

OBJECTIVES

In the present study, the possible protective role for endogenous ovarian hormones against learning and memory impairment as well as brain tissues oxidative damage induced by lipopolysachride (LPS) was investigated in rats.

MATERIALS AND METHODS

THE RATS WERE DIVIDED INTO FOUR GROUPS: Sham-LPS, Ovariectomized (OVX)-LPS, Sham, and OVX. The animals of sham group were in proestrous phase in which the serum concentration of estradiol is high. The Sham-LPS and OVX-LPS groups were treated with LPS (250 µg/kg) before acquisition. The animals were examined using passive avoidance (PA) test. The brains were then removed and malondialdehyde (MDA) and total thiol groups concentrations were measured.

RESULTS

The time latency to enter the dark compartment by OVX-LPS group was shorter than that of OVX at both first and 24th hours after the shock (P < 0.05 - P < 0.001). In Sham-LPS and OVX-LPS groups, total thiol concentration in hippocampal and cortical tissues were significantly lower while MDA concentrations were higher than that of Sham and OVX groups (P < 0.05 - P < 0.001). ). The hippocampal MDA concentration in OVX-LPS group was higher than Sham- LPS group (P < 0.01).

CONCLUSIONS

Brain tissue oxidative damage contributed in deleterious effects of LPS on learning and memory. Some protective effects for the endogenous ovarian hormones against damaging effects of LPS on learning and memory function, as well as brain tissues oxidative damage could be postulated; however, it needs more investigation.

Contribution of estradiol in sex-dependent differences of pentylenetetrazole-induced seizures in rats

In the present study the contribution of estradiol in sex-dependent differences of pentylenetetrazole (PTZ)-induced seizures was investigated in rats. The rats were divided into four groups: 1) sham, 2) ovariectomized (OVX), 3) ovariectomized-estradiol (OVX-Est) and 4) male. The OVX-Est group received estradiol valerate (2 mg/kg; i.m/4 weeks) while, male, sham and OVX groups received vehicle. The animals were injected by PTZ (90 mg/kg). The latencies to minimal clonic seizures (MCS) and generalized tonic-clonic seizures (GTCS), were recorded. Serum 17β-estradiol and testosterone levels were also determined using an Elisa kit. GTCS latency in OVX rats was higher than in sham-operated animals (P < 0.05). MCS and GTCS latency in the male group was significantly higher than in the sham, OVX and OVX-Est groups (P < 0.001 and P < 0.01). There was no significant difference in MCS or GTCS latencies among OVX-Est, sham and OVX groups. Serum 17β-estradiol level in the OVX group was significantly lower than in the sham (P < 0.01) and in the OVX-Est group it was higher than in the sham, OVX and male groups (P < 0.01 and P < 0.001). Serum testosterone level in the male group was significantly higher than in all the other three groups (P < 0.001). It seems that testosterone probably has a more efficient role than estradiol in the gender dependent difference in seizure caused by PTZ in rats.

Anticonvulsant effects of Fuzi total alkaloid on pentylenetetrazole-induced seizure in mice

We investigated the anticonvulsant effect of acute Fuzi total alkaloid (FTA) in seizure induced by the GABAA-receptor antagonist pentylenetetrazole (PTZ). FTA significantly increased the seizure latency and decreased the mortality in PTZ-treated mice. Administration of PTZ increased c-Fos expression in the hippocampus, medial prefrontal cortex, and piriform cortex; and this PTZ-induced effect was inhibited by FTA in a dose-dependent manner. Furthermore, the effects of FTA on PTZ-induced seizure and c-Fos expression were reversed by the GABAA/benzodiazepine receptor-selective antagonist flumazenil. These findings suggest that the anticonvulsant effects of FTA may be related to modulation of GABAA-benzodiazepine receptor complex.

Tamoxifen mimics the effects of endogenous ovarian hormones on repeated seizures induced by pentylenetetrazole in rats

In the present study, the effects of tamoxifen on pentylenetetrazole (PTZ)-induced repeated seizures and hippocampal neuronal damage in ovariectomized rats were investigated. Thirty seven virgin female Wistar rats were divided to: (1) control, (2) sham-PTZ, (3) sham-PTZ-tamoxifen (sham-PTZ-T), (4) Ovariectomized -PTZ (OVX-PTZ) and (5) OVX-PTZ-tamoxifen (OVX-PTZ-T) groups. The animals of groups 3 and 5 were injected by tamoxifen (10 mg/kg) on 7 consecutive days. After 7 days of tamoxifen injection, they also were then injected by tamoxifen 30 min prior each PTZ injection. PTZ (40 mg/kg) was injected on 6 consecutive days and the animal behaviors were observed for 60 min. The histological methods were then used to determine dark neurons in hippocampus. A significant decrease in the seizure score was seen in OVX-PTZ group compared to Sham-PTZ. The animals of OVX-PTZ-T group had a significant higher seizure score compared to OVX-PTZ group. The dark neurons in DG of OVX group were lower than sham group (p<0.01). The numbers of dark neurons in CA1 area of OVX-PTZ-T group was higher than OVX-PTZ group (p<0.05) compared to control, the numbers of dark neurons in CA3 area showed a significant increase in Sham-PTZ and OVX-PTZ group (p<0.05 and p<0.01 respectively). Dark neurons in OVX-PTZ-T group were higher than OVX-PTZ group (p<0.05). It is concluded that pretreatment of the ovariectomized rats by tamoxifen increased PTZ-induced seizure score and dark neurons. It might be suggested that tamoxifen has agonistic effects for estrogen receptors to change the seizure severity.

Effects of different extracts of Eugenia caryophyllata on pentylenetetrazole-induced seizures in mice

OBJECTIVE

To investigate the possible anticonvulsant effect of different extracts of Eugenia caryophyllata (clove) on pentylenetetrazole (PTZ)-induced seizures in mice.

METHODS

The animals were divided into saline, 50, 100, 250 and 500 mg/kg of aqueous extract, 50, 100, 250 and 500 mg/kg of ethanolic extract, and 50, 100, 250 and 500 mg/kg of chloroformic extract of clove groups. The extracts or saline were injected 60 min before each PTZ injection. Latency to the first minimal clonic seizure (MCS) and generalized tonic-clonic seizure (GTCS) and the percent of mortality were recorded.

RESULTS

Aqueous extract of clove at doses of 50, 100, 250 and 500 mg/kg significantly extended the MCS and GTCS latency (P<0.05). The MCS latency in mice treated with 50, 100 and 250 mg/kg of the ethanolic extract was significantly increased (P<0.05). The GTCS latency in mice treated with 50, 100, 250 and 500 mg/kg of ethanolic extract was significantly higher than that of the saline-treated group (P<0.05). There were no significant differences in MCS and GTCS latency between mice treated with different chloroformic extract of clove or saline.

CONCLUSION

The aqueous and ethanolic extracts of clove could inhibit the PTZ-induced convulsion, and this plant has the potential to be used as a new therapeutic agent for control of seizures. The exact mechanisms and the active compounds that are responsible for the anticonvulsive effect need to be clarified in future studies.

Estrogen-dependent effect of soy extract on pentylenetetrazole-induced seizures in rats

OBJECTIVE

To study the different effects of soy extract on pentylenetetrazole (PTZ)-induced seizures in the presence and absence of ovarian hormones in rats, and the gender-dependent differences in the effects of phytoestrogens on behavior.

METHODS

Male and female Wistar rats were randomly divided into nine groups with eight in each, namely, male-saline (M-saline), male-low-dose soy (M-LDS), male-high-dose soy (M-HDS), sham-saline (Sh-saline), sham-low-dose soy (Sh-LDS), sham-high-dose soy (Sh-HDS), ovariectomized-saline (OVX-saline), ovariectomized-low-dose soy (OVX-LDS) and ovariectomized-high-dose soy (OVX-HDS). The rats of groups 7 to 9 were ovariectomized under ketamine anesthesia. The rats of groups 2, 5 and 8 were treated by 20 mg/kg of soy extract while the animals of groups 3, 6 and 9 received 60 mg/kg of soy extract for two weeks. In groups 1, 4 and 7, saline was injected instead of soy extract. The animals were then injected by a single dose of PTZ (90 mg/kg body weight, intraperitoneally) and placed in a plexiglas cage and the latency to minimal clonic seizure (MCS) and generalized tonic-clonic seizure (GTCS) was recorded.

RESULTS

Both MCS and GTCS latency in M-LDS and M-HDS groups was significantly lower than that in M-saline group (P<0.05 or P<0.01). Treatment for female sham rats by soy extract did not affect MCS and GTCS latency. The animals of OVX-LDS and OVX-HDS groups had lower MCS and GTCS latency in comparison with OVX-saline group (P<0.05 or P<0.01).

CONCLUSION

It is concluded that the phytoestrogens of soy affect seizure severity induced by PTZ, but their effects are different in the presence or absence of ovarian hormones. However, further studies are necessary to be done.

Decreased nitric oxide levels in the hippocampus may play a role in learning and memory deficits in ovariectomized rats treated by a high dose of estradiol

The effects of a high estradiol dose on memory and on nitric oxide metabolites in hippocampal tissues were investigated. Sham-Est and OVX-Est Groups were treated with 4 mg/kg of estradiol valerate for 12 weeks. Time latency and path length were significantly higher in the Sham-Est and OVX-Est Groups than in the Sham and OVX Groups, respectively (p<0.001). The animals in the Sham-Est and OVX-Est Groups spent lower time in the target quadrant (Q1) than those of the Sham and OVX Groups during the probe trial test (p<0.05 and <0.001, respectively). Significantly lower nitric oxide metabolite levels in the hippocampi of the Sham-Est and OVX-Est Groups were observed than in the Sham and OVX ones (p<0.001). These results suggest that decreased nitric oxide levels in the hippocampus may play a role in the learning and memory deficits observed after treatment with a high dose of estradiol, although the precise underlying mechanisms remain to be elucidated.

Different effects of scopolamine on learning, memory, and nitric oxide metabolite levels in hippocampal tissues of ovariectomized and Sham-operated rats

Different effects of scopolamine on learning, memory, and nitric oxide (NO) metabolites in hippocampal tissues of ovariectomized (OVX) and sham-operated rats were investigated. The animals in the Sham-Scopolamine (Sham-Sco) and OVX-Scopolamine (OVX-Sco) Groups were treated with 2 mg/kg scopolamine before undergoing the Morris water maze, while the animals in the Sham and OVX Groups received saline. The time latency and path length were significantly higher in both the Sham-Sco and the OVX-Sco Groups, in comparison with the Sham and OVX Groups, respectively (p<0.001). Significantly lower NO metabolite levels in the hippocampi of the Sham-Sco Group were observed, compared with the Sham Group (p<0.001), while there was no significant difference between the OVX-Sco and OVX Groups. The decreased NO level in the hippocampus may play a role in the learning and memory deficits induced by scopolamine. However, it seems that the effect of scopolamine on hippocampal NO differs between situations of presence and absence of ovarian hormones.

Different effects of L-arginine on morphine tolerance in sham and ovariectomized female mice

OBJECTIVE

The roles of gonadal hormones and nitric oxide (NO) on the analgesic effects of morphine, tolerance to morphine, and their interactions have been widely investigated. In the present study, the effect of L-arginine (an NO precursor) on morphine tolerance in sham and ovariectomized (OVX) female mice was investigated.

METHODS

Forty mice were divided into sham and OVX groups. On the first day, a hot plate test ((55±0.2) °C; cut-off 30 s) was carried out as a base record 15 min before injection of morphine (10 mg/kg, subcutaneously (s.c.)) and was repeated every 15 min after injection. The sham group was then divided into two subgroups: sham-tolerance-L-arginine (Sham-Tol-LA) and sham-tolerance-saline (Sham-Tol-Sal) which received either L-arginine 50 mg/kg (intraperitoneally (i.p.)) or saline 10 ml/kg (i.p.), respectively, three times in a day for three consecutive days. Morphine tolerance was induced in animals by injecting 30 mg/kg morphine (s.c.) three times/day for three days. This treatment was also used for OVX subgroups. On the fifth day, the hot plate test was repeated. The analgesic effect of morphine was calculated as the maximal percent effect (MPE). The results were compared using repeated measure analysis of variance (ANOVA).

RESULTS

There was no significant difference in MPE between the OVX and sham groups. The MPEs in both the Sham-Tol-Sal and OVX-Tol-Sal groups were lower than those in both the sham and OVX groups (P<0.01). The MPE in the OVX-Tol-Sal group was greater than that in the Sham-Tol-Sal group (P<0.01). The MPE in the Sham-Tol-LA group was higher than that in the Sham-Tol-Sal group (P<0.01). However, there was no significant difference between the Sham-Tol-LA and sham groups or between the OVX-Tol-LA and OVX-Tol-Sal groups.

CONCLUSIONS

The results of the present study showed that repeated administration of morphine causes tolerance to the analgesic effect of morphine. L-arginine could prevent tolerance to morphine but its effect was different in the presence of ovarian hormones.

Repeated PTZ treatment at 25-day intervals leads to a highly efficient accumulation of doublecortin in the dorsal hippocampus of rats

BACKGROUND

Neurogenesis persists throughout life in the adult mammalian brain. Because neurogenesis can only be assessed in postmortem tissue, its functional significance remains undetermined, and identifying an in vivo correlate of neurogenesis has become an important goal. By studying pentylenetetrazole-induced brain stimulation in a rat model of kindling we accidentally discovered that 25±1 days periodic stimulation of Sprague-Dawley rats led to a highly efficient increase in seizure susceptibility.

METHODOLOGY/PRINCIPAL FINDINGS

By EEG, RT-PCR, western blotting and immunohistochemistry, we show that repeated convulsive seizures with a periodicity of 25±1 days led to an enrichment of newly generated neurons, that were BrdU-positive in the dentate gyrus at day 25±1 post-seizure. At the same time, there was a massive increase in the number of neurons expressing the migratory marker, doublecortin, at the boundary between the granule cell layer and the polymorphic layer in the dorsal hippocampus. Some of these migrating neurons were also positive for NeuN, a marker for adult neurons.

CONCLUSION/SIGNIFICANCE

Our results suggest that the increased susceptibility to seizure at day 25±1 post-treatment is coincident with a critical time required for newborn neurons to differentiate and integrate into the existing hippocampal network, and outlines the importance of the dorsal hippocampus for seizure-related neurogenesis. This model can be used as an in vivo correlate of neurogenesis to study basic questions related to neurogenesis and to the neurogenic mechanisms that contribute to the development of epilepsy.

The effect of chronic administration of L-arginine and L-NAME on morphine-induced antinociception in ovariectomized rats

OBJECTIVE

The role of ovarian hormones and nitric oxide on morphine-induced antinociception and their interaction have been widely investigated. The results of previous study showed that nitric oxide synthase inhibition differently affects morphine-induced antinociception in male and female rats. The present study was carried out to evaluate the different effects of chronic administration of L-arginine (LA) and L-NAME (LN) on morphine-induced antinociception in ovariectomized (OVX) and naive female rats.

MATERIALS AND METHODS

Sixty female rats were randomly divided into six groups (n = 10) as follows: (1) sham, (2) OVX, (3) sham-LA (4) sham-LN (5) OVX-LA, and (6) OVX-LN. The animals of sham-LA and OVX-LA groups received daily injection of 200 mg/kg LA (i.p.) during 6 weeks, while in sham-LN and OVX-LN groups, the animals were treated with 10 mg/kg LN (i.p.). The animals of sham and OVX groups received 2 ml/kg saline (i.p.) instead of LA and LN. Finally, all the animals were tested on the hot plate test (52 ± 0.2°C; cut-off time 80 seconds) for evaluating the antinociceptive effects of morphine. The hot plate test was performed as three base records with a 15-min interval before the injection of morphine (10 mg/kg; s.c.) following which it was repeated every 15 min after injection. Analgesic effect of morphine was quantified as maximal percent effect (MPE). Base reaction latency times (seconds) before the injection of morphine and MPE after the injection of morphine were compared using repeated-measure analysis of variance (ANOVA) followed by post-hoc Tukey's test. Differences were considered statistically significant when P < 0.05.

RESULTS

Before injection of morphine, there was no significant difference observed between sham and OVX groups in three recorded base reaction latency times. The base reaction latency times in sham-LA group were significantly higher than those of sham group (P < 0.001). In sham-LN group, the base reaction latency times were nonsignificantly lower than those of sham group (P = 0.095). There was no significant difference between OVX-LA group and OVX group. In OVX-LN group, three base reaction latency times were nonsignificantly lower than those of OVX group (P = 0.077). MPE in sham-LN group was higher than that of sham group (P < 0.05); however, there was no significant difference between sham-LA and sham groups.

CONCLUSION

It is concluded that NO has a role in pain perception and the analgesic effect of morphine. The effect of NO might be differing in the presence or absence of ovarian hormones, but further investigations need to be done.

Chronic treatment with the nitric oxide synthase inhibitor, L-NAME, attenuates estradiol-mediated improvement of learning and memory in ovariectomized rats

INTRODUCTION

The role of ovarian hormones and nitric oxide in learning and memory has been widely investigated.

OBJECTIVE

The present study was carried out to evaluate the effect of the nitric oxide synthase (NOS) inhibitor, N (G)-nitro-L-arginine methyl ester (L-NAME), on the ability of estradiol to improve learning in OVX rats using the Morris water maze.

METHODS

Forty rats were divided into five groups: (1) ovariectomized (OVX), (2) ovariectomized-estradiol (OVX-Est), (3) ovariectomized-L-NAME 10 (OVX-LN 10), (4) ovariectomized-L-NAME 50 (OVX-LN 50) and (5) ovariectomized-estradiol-L-NAME 50 (OVX-Est-LN 50). The animals in the OVX-Est group were treated with a weekly injection of estradiol valerate (2 mg/kg; i.m.). The OVX-LN 10 and OVX-LN 50 groups were treated with daily injections of 10 and 50 mg/kg L-NAME (i.p.), respectively. The animals in the OVX-Est-LN 50 group received a weekly injection of estradiol valerate and a daily injection of 50 mg/kg L-NAME. After 8 weeks, all animals were tested in the Morris water maze.

RESULTS

The animals in the OVX-Est group had a significantly lower latency in the maze than the OVX group (p<0.001). There was no significant difference in latency between the OVX-LN 10 and OVX-LN 50 groups in comparison with the OVX group. The latency in the OVX-Est-LN 50 group was significantly higher than that in the OVX-Est group (p<0.001).

CONCLUSION

These results show that L-NAME treatment attenuated estradiol-mediated enhancement of spatial learning and memory in OVX rats, but it had no significant effect in OVX rats without estrogen, suggesting an interaction of nitric oxide and estradiol in these specific brain functions.