The effect of GABAergic system activity on hyperthermia-induced seizures in rats

A review for the pharmacological effects of paeoniflorin in the nervous system

Paeoniflorin, a terpenoid glycoside compound extracted from Paeonia lactiflora Pall, shows preventive and therapeutic effects in various types of nervous system disorders. However, to date, no comprehensive knowledge on the pharmacological effects of paeoniflorin on the nervous system is available online. Clarification of this issue may be useful for the development of paeoniflorin as a new drug for the treatment of nervous system disorders. To this end, the authors summarize the pharmacological aspects of paeoniflorin and its possible mechanisms, such as restoration of mitochondrial function; inhibition of neuroinflammation, oxidative stress, and cellular apoptosis; activation of adenosine A1 receptor, cAMP response element-binding protein (CREB) and extracellular signal-regulated kinase 1/2 (ERK1/2); or enhancement of brain-derived neurotrophic factor and serotonin function, in the prevention of disorders such as cerebral ischemia, subarachnoid hemorrhage, vascular dementia, Alzheimer's disease, Parkinson's disease, depression, post-traumatic syndrome disorder, and epilepsy, by reviewing the previously published literature.

The influence of temperature on adult zebrafish sensitivity to pentylenetetrazole

Pentylenetetrazole (PTZ) is one of the most valuable drugs used to induce seizure-like state in zebrafish especially considering the pharmacological screening for anticonvulsants and the study of basic mechanisms of epilepsy. Here, the effect of gender, weight and changes in temperature on latency to adult zebrafish reach classical seizure states induced by PTZ (10mM) was evaluated. Gender and weight (200-250mg versus 400-500mg) did not affect the profile of response to PTZ. When water temperature was changed from 22 to 30°C the lower temperature increased the latency time to reach seizure states and the higher temperature significantly decreased it, in comparison to the control group maintained at 26°C. The blockage of kainate receptors by DNQX (10μM) were unable to prevent the increased susceptibility of adult zebrafish exposed to hyperthermia and PTZ-induced seizures. The NMDA block by MK-801 (2.5μM) prevented the additive effect of hyperthermia on PTZ effects in adult zebrafish. This report emphasize that PTZ model in adult zebrafish exhibits no confounder factors from gender and weight, but water temperature is able to directly affect the response to PTZ, especially through a mechanism related to NMDA receptors.

Anticonvulsive effect of paeoniflorin on experimental febrile seizures in immature rats: possible application for febrile seizures in children

Febrile seizures (FS) is the most common convulsive disorder in children, but there have been no clinical and experimental studies of the possible treatment of FS with herbal medicines, which are widely used in Asian countries. Paeoniflorin (PF) is a major bioactive component of Radix Paeoniae alba, and PF-containing herbal medicines have been used for neuromuscular, neuropsychiatric, and neurodegenerative disorders. In this study, we analyzed the anticonvulsive effect of PF and Keishikashakuyaku-to (KS; a PF-containing herbal medicine) for hyperthermia-induced seizures in immature rats as a model of human FS. When immature (P5) male rats were administered PF or KS for 10 days, hyperthermia-induced seizures were significantly suppressed compared to control rats. In cultured hippocampal neurons, PF suppressed glutamate-induced elevation of intracellular Ca²⁺ ([Ca²⁺]_i), glutamate receptor-mediated membrane depolarization, and glutamate-induced neuronal death. In addition, PF partially suppressed the elevation in [Ca²⁺]_i induced by activation of the metabotropic glutamate receptor 5 (mGluR5), but not that mediated by α-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid (AMPA) or N-methyl-D-aspartate (NMDA) receptors. However, PF did not affect production or release of γ-aminobutyric acid (GABA) in hippocampal neurons. These results suggest that PF or PF-containing herbal medicines exert anticonvulsive effects at least in part by preventing mGluR5-dependent [Ca²⁺]_i elevations. Thus, it could be a possible candidate for the treatment of FS in children.

Administration of neurotoxic doses of MDMA reduces sensitivity to ethanol and increases GAT-1 immunoreactivity in mice striatum

RATIONALE

Mice with reduced dopamine activity following neurotoxic doses of 3,4-methylenedioxymethamphetamine (MDMA, 'ecstasy') consume more ethanol (EtOH) and show greater preference for EtOH. In keeping with human studies and other animal models where alcohol consumption and preference are also high, MDMA treatment will reduce sensitivity to certain physiological effects of EtOH.

OBJECTIVE

We have examined the sensitivity to the acute effects of EtOH in MDMA-lesioned mice and the effects of EtOH on striatal gamma-aminobutyric acid (GABA) accumulation and expression of GABA subtype-1 transporter (GAT-1).

METHODS

C57BL/6J mice were injected with neurotoxic MDMA (30 mg/kg, three times, every 3 h, i.p.). Seven days later, mice were given EtOH (3 g/kg, i.p.) to determine the loss of righting response and the development of rapid tolerance to the hypothermic effect of EtOH. The effect of EtOH on the striatal accumulation of GABA after inhibiting GABA transaminase and on GAT-1 immunoreactivity was also determined.

RESULTS

Mice pre-treated with a neurotoxic dose of MDMA were less sensitive to the sedative-hypnotic effect of acute EtOH and exhibited alterations in the development of rapid tolerance to the hypothermic effect of EtOH. These animals showed an increase in striatal GAT-1 immunoreactivity. EtOH reduced GABA concentration in the striatum of non-lesioned mice, an effect not observed in MDMA-lesioned mice.

CONCLUSION

These findings indicate that mice with a MDMA-induced dopaminergic lesion show increased expression of striatal GAT-1 that may contribute to the lower sensitivity to EtOH-induced sedative effects and the resistance to the development of rapid tolerance to hypothermia produced by EtOH.

Interleukin-10 is associated with resistance to febrile seizures: genetic association and experimental animal studies

PURPOSE

Febrile seizures (FS) are the most common form of childhood convulsions. Many reports have shown that a proinflammatory cytokine, interleukin-1 (IL-1) beta, may have a facilitatory effect on the development of FS. We have previously shown that the IL1B -511C/T single nucleotide polymorphism (SNP) is associated with simple FS of sporadic occurrence. The balance between pro- and antiinflammatory cytokines influences the regulation of infections and could, therefore, play a role in the pathogenesis of FS. Here, to determine whether pro- and antiinflammatory cytokine genes are responsible for the susceptibility to FS, we have performed an association study on functional SNPs of cytokine genes in FS patients and controls.

METHODS

The promoter SNPs of four inflammatory cytokine genes (IL6 -572C/G, IL8 -251A/T, IL10 -592A/C and TNFA -1037C/T) were examined in 249 patients with FS (186 simple and 63 complex FS) and 225 controls. Because the IL10 -592 SNP showed a positive association with FS, two additional SNPs (IL10 -1082A/G and -819T/C) were subjected to haplotype analysis. Furthermore, we examined the in vivo role of IL-10 in hyperthermia-induced seizures using immature animal models.

RESULTS

The frequencies of the IL10 -592C allele and -1082A/-819C/-592C haplotype were significantly decreased in FS as compared with in controls (p = 0.014 and 0.013, respectively). The seizure threshold temperature in the IL-10-administered rats was significantly higher than that in the saline-treated control ones (p = 0.027).

CONCLUSIONS

The present study suggests that IL-10 is genetically associated with FS and, contrary to IL-1beta, confers resistance to FS.

MDMA (Ecstasy) controls in concert a group of genes involved in GABA neurotransmission

In several countries, 3,4-methylenedioxymethamphetamine (MDMA) is currently the most abundant psychoactive recreational drug. MDMA induces numerous neuropsychiatric behaviors, serotonergic neuron degeneration, programmed death of cultured cells, hyperthermia and occasional fatality. Using gene expression analysis in MDMA-treated mice, we identified changes in gamma-amino butyric acid (GABA) transporters and synaptotagmins I and IV. Additional experiments showed decreases in mRNAs encoding septin and dystrophin. Although belonging to different gene families, it is striking that these four protein groups are implicated in neurotransmission of GABA, a major inhibitory neurotransmitter involved in thermoregulation. MDMA may control these genes in a combined fashion, assigning GABA a pivotal role in MDMA activities.

The genetics of febrile seizures and related epilepsy syndromes

Febrile seizures (FS) may represent the most common seizure disorder in childhood and are known to be associated with putative genetic predispositions. Nevertheless, molecular genetic approaches toward understanding FS have been just initiated this decade. Recently, several genetic loci for FS have been mapped thereby assuring the genetic heterogeneity of FS. However, the exact molecular mechanisms of FS are yet to be elucidated. Genetic defects have been recently identified in autosomal dominant epilepsy with FS plus or generalized epilepsy with FS plus. The underlying mutations were found in genes encoding several Na+ channel subunits and the gamma2 subunit of gamma amino-butyric acid (GABA)A receptors in the brain. Furthermore, both channels are also associated with severe myoclonic epilepsy in infancy, where the seizure attacks often begin with prolonged FS and are precipitated by fever even afterwards. Na+ channels are associated with other temperature-sensitive disorders, and GABA(A) receptors are known to play an important role in the pathogenesis of FS. These lines of evidence suggest the involvement of various Na+ channels, GABA(A) receptors and additional auxiliary proteins in the pathogenesis of frequent FS and even in simple FS. This hypothesis may facilitate our understanding of the genetic background of FS.

Genetic abnormalities underlying familial epilepsy syndromes

Genetic defects have been recently identified in certain inherited epilepsy syndromes in which the phenotypes are similar to common idiopathic epilepsies. Mutations in the neuronal nicotinic acetylcholine receptor 4 and 2 subunit genes have been detected in families with autosomal dominant nocturnal frontal lobe epilepsy. Both receptors are components of neuronal acetylcholine receptor, a ligand-gated ion channel in the brain. Furthermore, mutations of two K+-channel genes were also identified as the underlying genetic abnormalities of benign familial neonatal convulsions. Mutations in the voltage-gated Na+-channel 1, 2 and 1 and the gamma aminobutyric acid (GABAA) receptor 2 subunit genes were found as a cause of generalized epilepsy with febrile seizures plus, a clinical subset of febrile convulsions. Na+-channels, GABAA receptor and their auxiliaries may be involved in the pathogenesis of this subtype and even in simple febrile convulsions. Mutation of a voltage-gated K+-channel gene can cause partial seizures associated with periodic ataxia type 1 and some forms of juvenile myoclonic epilepsy and idiopathic generalized epilepsy can result from mutations of a Ca2+-channel. This line of evidence suggests the involvement of channels expressed in the brain in the pathogenesis of certain types of epilepsy. Our working hypothesis is to view certain idiopathic epilepsies as disorders of ion channels, i.e. 'channelopathies'. Such hypothesis should provide a new insight to our understanding of the genetic background of epilepsy.