Investigation of the effects of Satureja edmondi on memory impairment caused by chemical kindling in adult male rats

Gelavij Mahmoodi; Somayeh Bohlouli

doi:10.4103/jrptps.JRPTPS_89_20

ORIGINAL ARTICLE

Year : 2021 | Volume : 10 | Issue : 2 | Page : 194-197

Investigation of the effects of Satureja edmondi on memory impairment caused by chemical kindling in adult male rats

Gelavij Mahmoodi¹, Somayeh Bohlouli²
¹ Department of Biology, College of Basic Science, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
² Department of Veterinary, College of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran

Date of Submission	25-Jul-2020
Date of Acceptance	04-May-2021
Date of Web Publication	17-Dec-2021

Correspondence Address:
Dr. Somayeh Bohlouli
Department of Veterinary, College of Agriculture, Kermanshah Branch, Islamic Azad University, Kermanshah.
Iran

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jrptps.JRPTPS_89_20

Abstract

Introduction: Epilepsy causes neuronal damage that disturbs normal brain functioning, especially in the hippocampal formation. In addition, it has been shown that cognitive inconsistencies, changes in emotional behavior, and neuronal loss in the hippocampus occur during pentylenetetrazole (PTZ)-induced kindling. So, the purpose of the present research was to investigate whether administration of Satureja edmoni is able to prevent memory impairment, caused by PTZ-induced kindling in adult male rats. Materials and Methods: In this study, male rats were kindled by repeated (two or three) injection of PTZ intraperitoneally (i.p.) (25 mg/kg); then all animals in the extract groups were treated with 100, 200, or 400 mg/kg of S. edmondi. For behavior assessment, an inhibitory passive avoidance task was used. Results: Our results showed that animals in the kindled group took less time to enter dim hutch than control rats. There was a significant difference in step-through latency (STL) recorded from group of rats with PTZ-induced kindling treated with S. edmondi at concentrations 100 and 200 mg/kg and control rats, but differences between STL of PTZ-induced kindling animals treated with S. edmondi 400 mg/kg vs. control rats were not significant. Conclusion: In this study, we observed that PTZ induced impairing effects on passive avoidance memory; in contrast, administration of S. edmondi could abolish the impairment effect of epilepsy on memory.

Keywords: Kindling, memory, rat, Satureja edmondi

How to cite this article:
Mahmoodi G, Bohlouli S. Investigation of the effects of Satureja edmondi on memory impairment caused by chemical kindling in adult male rats. J Rep Pharma Sci 2021;10:194-7

How to cite this URL:
Mahmoodi G, Bohlouli S. Investigation of the effects of Satureja edmondi on memory impairment caused by chemical kindling in adult male rats. J Rep Pharma Sci [serial online] 2021 [cited 2023 Sep 26];10:194-7. Available from: https://www.jrpsjournal.com/text.asp?2021/10/2/194/332787

Introduction

Epilepsy is one of the most common and chronic brain disorders that affect about 1% of the general population.^[1] Epilepsy causes neuronal damage that disturbs normal brain functioning, especially in the hippocampal formation.^[2]

Pentylenetetrazol (PTZ), as a non-competitive chloride ionophore complex of the gamma-amino-butyric-acid (GABA) antagonist, is used as seizure chemical stimulus in the experimental study in animals.^[3] A periodic systemic injection of PTZ induces an acute, severe seizure in animals.^[4]

During PTZ-induced kindling, behavioral, neurophysiological, and neurochemical symptoms are changeable from person to person.^[5]

PTZ has the inhibitory effect on some neurotransmitters such as the GABAergic and glutamatergic systems.^[6] Control of neuronal excitability and epileptogenesis are also affected by PTZ.

Research findings indicate that kindling-induced seizures caused cognitive inconsistencies, changes in emotional behavior, and neuronal loss in the hippocampus^[7],[8] that cause impairment in cognitive process in the hippocampus.^[9] According to Lamberty and Klitgaard,^[10] PTZ-induced kindling interferes in spatial memory.

Twelve 12 species of the genus Satureja are known; some of them are endemic to Iran, which includes S. edmondi, S. intermedia, S. sahendica, S. isophylla, S. kallarica, S. atropatana, S.bachtiarica, and S. khuzistanica. This plant is a perennial and bushy aromatic herb that grows 50 cm high with yellow-colored flowers, dense white villous hairs, and a dense covering of punctuate glands on both leaf surfaces. Flowering occurs in autumn at late September and October.^[11]S. edmondi is grown in the west of Iran, Kermanshah and usually grows on rock. S. edmondi is often used to treat digestive and respiratory disorders such as state of enteritis, chronic ulcer, and asthma.^[12]

According to the study carried out by Ghorbanpour et al.,^[13] essential oils of Satureja species such as S. edmondi include predominant compounds such as p-cymene, carvacrol, p-cymene, thymol, and their precursors and γ-terpinene.

Various activities of carvacrol are known, which include antimicrobial, antioxidant, anticandidal, and anti-inflammatory properties.^[14],[15] The hydrophobic terpenoid carvacrol suppresses L-type Ca2+in a concentration-dependent way.^[16]

The aim of the present study was to determine whether administration of S. edmondi is able to prevent memory impairment, caused by PTZ-induced kindling in adult male rats.

Materials and Methods

Animals and treatment

For this experimental study, adult Wistar male rats (250–300 g) (Razi Institute, Tehran, Iran) were housed in a Plexiglass hutch. They had degage disposal to food and water and kept at the standard animal room. The animals were kindled by transfusion of 25 mg/kg (i.p.) PTZ (Sigma, St. Louis, MO, USA), 1 mL/kg for every 15 min until seizures happened (two or three transfusion). After injection, seizure activity was seen for 45 min and recorded; briefly, stage 0, no response; stage 1, ear and facial twitching; stage 2, myoclonic jerks, without rearing; stage 3, myoclonic jerks, rearing; stage 4, turn over into side position, clonic-tonic seizures; stage 5, turn over into back position, generalized tonic-clonic seizures. The rats that reached stage 4/5 according to the scale change by Becker et al.^[17],[18] were considered as kindled animals. In the extract groups, all animals received Satureja hydroalcoholic extract three times (first time: 1 h after kindling, second time: 24 h after kindling, and third time: 1 h before training session). Control animals received saline instead.

Preparation of plant extract

S. edmondi was obtained from Dallaho Mountains in the west of Kermanshah, Iran. The plant was identified and authenticated by Dr Sharifi, Assistant Professor, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran. S. edmondi leaves were dried and powdered. About 200 g of powdered plant was added to 400 cc 70% ethanol and were left to macerate at room temperature for 4 h. Then, the soaked plant was extracted by the percolation method; it was removed from the percolator, filtered by a Whatman filter paper (No. 4), and then dried under reduced pressure at 37°C with a rotator evaporator.

Behavioral experiment

The passive avoidance memory was assessed in the shuttle box that includes one light and one dim hutch of the same size portioned by a moveable tumbrel door. In the dim hutch, the floor had stainless-steel rods with 0.5 cm diameter, parted with 1 cm space. Using an isolated stimulator, the alternative electric shocks (50 Hz, 3 s, 0.7 mA) intensity acrimony was transferred to the floor of the dim hutch.

Training

The training protocol was the same as our previous research.^[19] The animals were permitted to become habituated to the lab milieu at least 30 min before the training phase. Then, each animal was gently placed in the light hutch; 10 s later, by opening the tumbrel door, animal was allowed to go to the dim hutch. Each rat which waited more than 100 s in the light hutch was removed. For the animal that passed with all four paws to another compartment, the door was closed and a foot shock (50 Hz, 0.7 s, 1 mA) was immediately delivered to the grid floor of the dim hutch. Formerly, the rat was removed from the apparatus and the process was repeated after 2 min. When the rat stayed in the light hutch for 120 s, the training was finished; after the training session, rats were placed temporarily into its home cage. The maximum trials of training session for each rat were three times.

Retention test

Twenty-four hours after final training, retention testing was implemented. Each rat was quietly positioned in the light hutch and after 10 s the door was opened. The latency time of animal to enter the dim hutch step-through latency (STL) was recorded, and the takeoff point was 600 s. No electric shock was applied in the testing day.

Statistical analysis

The results were statistically estimated by one-way analysis of variance (ANOVA) and were presented as means ± SEM. Using post hoc Tukey’s test, additional analysis for multiple comparisons was carried out. In all evaluations, P < 0.05 was considered the level of statistical significance.

Results

Effect of PTZ-induced kindling on passive avoidance memory

As shown in [Figure 1A], the result of our experiment indicated that the kindled group required less time to enter the dark chamber than those in the control group (t₁₄ = 3.1, P = 0.00) [Figure 1A]. [Figure 1B] shows that time spent in the dark chamber in the kindled group was higher than that spent in the control group (t₁₄ = 6.7, P = 0.00).

Figure 1: (A) The effect of PTZ-induced kindling on STL. The retention latencies of kindled rats were significantly reduced compared with control rats. Each bar represents mean± SEM, eight rats were in each group.***P<0.001. (B) The effect of PTZ kindling on time spent in the dark chamber. Time spent in the dark chamber in the kindled group was significantly increased compared with the control group. All rats were tested 24 h after the training session. Each bar represents mean± SEM, n=8 in each group, ***P<0.001

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Administration of S. edmondi eliminates the impairment effect of PTZ-induced kindling on passive avoidance memory

One-way ANOVA showed that there was a significant difference in STL recorded from group of rats with PTZ-induced kindling treated with S. edmondi at concentrations 100 and 200 mg/kg and control rats, but it did not show significant differences. There were no significant differences between STL recorded from PTZ-induced kindling treated with S. edmondi 400 mg/kg vs. control rats (F_{4, 39} = 7.88; P = 0.00; [Figure 2A]). Similar results were observed for spending time in the dark chamber (F_{4, 39} = 13.83; P = 0.00; [Figure 2B]). The results show that S. edmondi could abolish the impairment effects of PTZ-induced kindling on passive avoidance learning.

Figure 2: (A) The effect of i.p. administration of S. edmondi on inhibitory avoidance response in control and kindled rats that received different doses (0,100, 200, or 400 mg/kg) of Satureja extract. Three groups of rats (n=8 each) received Satureja extract (100, 200, or 400 mg/kg) for three times (after 1 and 24 h after kindling and also 1 h before training). All animals were tested 24 h after the training session. Each bar represents mean± SEM. *P<0.05, ***P<0.001. (B) The effect of i.p. administration of S. edmondi on the time spent in the dark chamber. Three groups of rats received Satureja extract (100, 200, or 400 mg/kg) for three times (after 1 and 24 h after kindling and also 1 h before training). All rats were tested 24 h after the training session. Each bar represents mean± SEM, n=8 in each group. *P<0.05 and ***P<0.001

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Discussion

In this present study, it was observed that administration of S. edmondi accomplishment could prevent/restrain the impairment effect of epilepsy on memory. This result is consistent with another study reporting that S. hortensis has anticonvulsant activity in the PTZ model in mice.^[20]

Another study reported that PTZ through altering in some neurotransmitter systems such as the GABAergic, glutamatergic, and glycine is able to induce epilepsy.^[21],[22] Kindling causes a decrease in the release of GABA in the hippocampus and a decrease in GABA receptor sensitivity.^[23] It is reported that an enhancement in glutamate neurotransmitter at the hippocampal region occurs during PTZ kindling.^[24] PTZ increases the density of glutamate receptor and activates N-methyl-D-aspartate (NMDA) receptors.^[25] It is suggested that PTZ induced seizures by glutamate receptor activation and inhibition of GABA neurotransmitters.^[23],[26]

Carvacrol is abundantly found in the essential oils of the Lamiaceae family. In addition, it was reported that carvacrol effectively suppresses Ca2+ current in neuronal membranes.^[27],[28] The blocking effect of the carvacrol on Ca2+ current resembles that of many conservative Ca2+-entry blocker agents, like verapamil or nifedipine.^[16] So it may be concluded that the protective effect of S. edmondi on PTZ-induced seizures is at least relatively due to the presence of carvacrol.

Quintans-Júnior et al.^[29] reported that carvacrol may reduce PTZ-induced seizures via inhibition of GABAergic transmission.

PTZ may activate NMDA receptor, leading to increased intracellular Ca²⁺. Ca²⁺ activates calcium-dependent proteins such as calcineurin, which ultimately impair learning and memory.^[30]

Therefore, with regard to the above, probably S. edmondi treatment by blocking Ca2+ current of calcium channels prevents the impairment effect of PTZ-induced kindling on passive avoidance memory.

Conclusion

Taken together, in this study, we demonstrated that S. edmondi could abolish the negative effect of epilepsy on memory. However, the exact mechanisms involved in the learning and memory prevention due to S. edmondi are not well known and may need further investigations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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