The Effects of Amiloride on Seizure Activity, Cognitive Deficits and Seizure-Induced Neurogenesis in a Novel Rat Model of Febrile Seizures.

Accumulating data suggest that sodium-hydrogen exchangers (NHEs) play a key role in modulating seizure activity by regulating neuronal pH in the brain. Amiloride, an inhibitor of NHEs, has been demonstrated to be effective in many seizure models, although its efficacy for prolonged febrile seizures (FS) remains unclear. In this study, we investigated whether amiloride could produce neuroprotective effects in a prolonged FS model in which FS were induced in rat pups at postnatal day 10 using a heated air approach. Amiloride was administered by intraperitoneal injection at three different doses (0.65, 1.3 and 2.6 mg/kg). Pretreatment with amiloride significantly delayed the onset of the first episode of limbic seizures, whereas posttreatment with amiloride decreased escape latency in the Morris water maze test compared to post-FS treatment with saline. Amiloride also inhibited seizure-induced aberrant neurogenesis. In conclusion, this study demonstrated the antiseizure activity of amiloride. In particular, posttreatment with amiloride resulted in cognitive improvement; this finding provides crucial evidence of the neuroprotective function of amiloride and of the therapeutic potential of amiloride in FS.

Astrocytic expression of cannabinoid type 1 receptor in rat and human sclerotic hippocampi.

Cannabinoid type 1 receptor (CB1R), which is traditionally located on axon terminals, plays an important role in the pathology of epilepsy and neurodegenerative diseases by modulating synaptic transmission. Using the pilocarpine model of chronic spontaneous recurrent seizures, which mimics the main features of mesial temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS) in humans, we examined the expression of CB1R in hippocampal astrocytes of epileptic rats. Furthermore, we also examined the expression of astrocytic CB1R in the resected hippocampi from patients with medically refractory mesial TLE. Using immunofluorescent double labeling, we found increased expression of astrocytic CB1R in hippocampi of epileptic rats, whereas expression of astrocytic CB1R was not detectable in hippocampi of saline treated animals. Furthermore, CB1R was also found in some astrocytes in sclerotic hippocampi in a subset of patients with intractable mesial TLE. Detection with immune electron microscopy showed that the expression of CB1R was increased in astrocytes of epileptic rats and modest levels of CB1R were also found on the astrocytic membrane of sclerotic hippocampi. These results suggest that increased expression of astrocytic CB1R in sclerotic hippocampi might be involved in the cellular basis of the effects of cannabinoids on epilepsy.

Interleukin-1 beta guides the migration of cortical neurons.

BACKGROUND: Proinflammatory cytokine interleukin-1beta (IL-1ß) is expressed at high levels in the developing brain and declines to low constitutive levels in the adult. However, the pathophysiological function of IL-1ß during brain development remains elusive. In this study, we investigated the role of IL-1ß in neuronal migration. METHODS: The Boyden transwell assay was used to examine the effects of IL-1ß on the migration of dissociated primary cortical neurons. To determine the role of IL-1ß in neuron leading process pathfinding, we employed a growth cone turning assay. In utero electroporation combined with RNAi technology was used to examine the neuronal migration in vivo during brain development in Sprague-Dawley rats. RESULTS: IL-1ß at concentrations ranging from 0.1 to 10 ng/mL in the lower chamber of a transwell induced a significant increase in the number of migrating neurons in a dose-dependent manner. When IL-1ß was simultaneously put in both the upper and lower chambers to eliminate the gradient, no significant differences in cell migration were observed. IL-1 receptor antagonist IL-1RA dose-dependently blocked the attractive effect of IL-1ß on neuronal migration. Microscopic gradients of IL-1ß were created near the growth cones of isolated neurons by repetitive pulsatile application of picoliters of a IL-1ß-containing solution with a micropipette. We found that growth cones exhibited a clear bias toward the source of IL-1ß at the end of a one hour period in the IL-1ß gradient. No significant difference was observed in the rate of neurite extension between IL-1ß and controls. We electroporated specific siRNA constructs against IL-1R1 mRNA into cortical progenitors at embryonic day 16 and examined the position and distribution of transfected cells in the somatosensory cortex at postnatal day 5. We found that neurons transfected with IL-1R1-siRNA displayed a severe retardation in radial migration, with about 83% of total cells unable to arrive at the upper cortical layers. CONCLUSIONS: Our study suggests an essential contribution of IL-1ß to neuronal migration during brain development, which provides a basis to understand the physiological roles of IL-1ß in the developing brain and could have significant implications for the prevention of some neurodevelopment disorders due to abnormal neuronal migration.