Post-ictal locomotor activity in three different rat models of epilepsy

Maturation-dependent behavioral deficits and cell injury in developing animals during the subacute postictal period

Prolonged early-life seizures are associated with disruptions of affective and cognitive function. Postictal disturbances, temporary functional deficits that persist for hours to days after seizures, have not yet been thoroughly characterized. Here, we used kainic acid (KA) to induce status epilepticus (SE) in immature rats at three developmental stages (postnatal day (P) 15, 21, or 30) and subsequently assessed spatial learning and memory in a Barnes maze, exploratory behavior in an open field, and the spatiotemporal distribution of cell injury during the first 7-10 days of the postictal period. At 1 day post-SE, P15-SE rats showed no deficit in the Barnes maze but were hyperexploratory in an open field compared with their littermate controls. In contrast, P21- and P30-SE rats exhibited markedly impaired performance in the Barnes maze and exhibited significantly reduced open field exploration suggestive of anxiety-like behavior. These behavioral changes were transient in P15 rats but more persistent in P21 and enduring in P30 rats after KA-SE. The time course of behavioral deficits in P21 and P30 rats was temporally correlated with the presence of neuronal injury in the lateral septal nuclei, amygdala, and ventral subiculum/CA1, regions involved in modulation of the hypothalamic-pituitary-adrenal stress response.

Dual protective effect of Passiflora incarnata in epilepsy and associated post-ictal depression

ETHNOPHARMACOLOGICAL RELEVANCE

Passiflora incarnata L. (Passifloraceae) has been used for the treatment of epilepsy in several traditional systems of medicine.

AIM OF THE STUDY

The aerial parts of Passiflora incarnata contain multiple bioactive metabolites such as, flavonoids (like, chrysin that show CNS depressant activity by agonizing GABA-benzodiazepine receptor), amino acids (like, GABA), harmala alkaloids (reversible monoamine oxidase-A inhibitor), etc. In view of this, the present study was designed to investigate dual protective effect of the hydroethanolic extract of Passiflora incarnata in pentylenetetrazol (PTZ)-induced seizure and associated post-ictal depression.

MATERIALS AND METHODS

Different groups of mice were administered with repeated subconvulsive doses of PTZ (50mg/kg; i.p.) at an interval of 5 days for 15 days. From 5th to 15th day the animals in different groups were administered daily with varying doses of hydroethanolic extract of Passiflora incarnata (150, 300, and 600mg/kg; i.p.), diazepam (2mg/kg; i.p.) and vehicle. On every 5th day, after PTZ treatment, seizure severity (score) was noted. Following convulsive episodes the locomotor activity (using actophotometer) and immobility period (using forced swim test) were also determined. On 15th day after behavioral assessment, the brain serotonin and noradrenaline levels were determined using spectrofluorometric methods.

RESULTS

Treatment with the extract significantly (p<0.05) reduced the seizure severity and immobility period as compared to vehicle control, in a dose and time-dependent manner. Moreover, the extract treatment retained the serotonin and noradrenaline levels of the brain.

CONCLUSIONS

The results of present study concluded that the hydroethanolic extract of Passiflora incarnata suppress PTZ-induced seizures, and ameliorates its associated post-ictal depression, which has been found to be get worsened with the standard antiepileptic drug, diazepam.

Postictal behavior after two types of cortical epileptic afterdischarges in rats

OBJECTIVE

The aim of this study was to determine if behavioral patterns during the postictal state depend on the type of seizure.

METHODS

Rhythmic electrical stimulation of sensorimotor cortex can elicit two types of epileptic afterdischarges (ADs) in adult rats: the spike-and-wave type accompanied by clonic convulsions, and a transition to a nonconvulsive type characterized by behavioral automatisms (mixed type). Rats in which stimulation did not induce ADs constituted the control group. The behavior of the animals was recorded for 20 minutes after the end of ADs or stimulation.

RESULTS

Stimulation elicited only shortlasting minimal changes in control rats. Spike-and-wave ADs led to alternation of normal and unsteady walking, a decrease in normal sitting and lying (rigid lying appeared instead), and wet dog shakes (WDS). Mixed-type ADs abolished normal walking and sitting and induced unsteady walking, rigid lying, and a substantial number of WDS.

CONCLUSIONS

Abnormal phenomena induced by the two types of ADs differ mostly quantitatively, but also qualitatively.

Brain vasopressin and sodium appetite

Intraventricular injections of vasopressin (VP) and antagonists with varying degrees of specificity for the VP receptors were used to identify the action of endogenous brain VP on 0.3 M NaCl intake by sodium-deficient rats. Lateral ventricular injections of 100 ng and 1 microg VP caused barrel rotations and a dramatic decrease in NaCl intake by sodium-deficient rats and suppressed sucrose intake. Intraventricular injection of the V(1)/V(2) receptor antagonist [d(CH(2))(5)(1),O-Et-Tyr(2),Val(4), Arg(8)]VP and the V(1) receptor antagonist [d(CH(2))(5)(1),O-Me-Tyr(2),Arg(8)]VP (MeT-AVP) significantly suppressed NaCl intake by sodium-deficient rats without causing motor disturbances. MeT-AVP had no effect on sucrose intake (0.1 M). In contrast, the selective V(2) receptor antagonist had no significant effect on NaCl intake. Last, injections of 100 ng MeT-AVP decreased mean arterial blood pressure (MAP), whereas 100 ng VP elevated MAP and pretreatment with MeT-AVP blocked the pressor effect of VP. These results indicate that the effects produced by 100 ng MeT-AVP represent receptor antagonistic activity. These findings suggest that the effect of exogenous VP on salt intake is secondary to motor disruptions and that endogenous brain VP neurotransmission acting at V(1) receptors plays a role in the arousal of salt appetite.

Long-term effects of repeated electroconvulsive shock on exploratory behaviour and seizure susceptibility to lidocaine in rats

Electroconvulsive shock (ECS) has anticonvulsant properties while a proconvulsant effect has not, so far, been documented. In the present experiments, we determine whether repeated ECSs lead to an increased seizure susceptibility to lidocaine (lignocaine) in rats. Furthermore, we investigated whether ECS will cause prolonged changes in the locomotion and exploratory activity of the animals. Two groups of rats received 18 ECSs: the first group (ECS-WEEKLY) was given ECS once a week, the second (ECS-DAILY) once a day. A third group (ECS-SHAM) received only sham ECS. Five, as well as 10 weeks after the last ECS, the ECS-WEEKLY group made significantly fewer "hole visits" in an eight hole box than did the ECS-SHAM group. The ECS-DAILY group also made fewer hole visits than the ECS-SHAM group, but the difference was only significant ten weeks after the last ECS. No significant difference in locomotor activity was found. Twelve weeks after the last ECS, all rats received an injection of a high dose of lidocaine (65 mg/kg i.p.). ECS was observed to have a significant effect on the number of animals convulsing in response to the lidocaine challenge. Sixty percent (6/10) of the animals in the ECS-WEEKLY group and 20% (2/10) of those in the ECS-DAILY group convulsed, whereas none of the animals (0/12) in the ECS-SHAM group had convulsions. Thus, the present study shows that ECS may induce prolonged changes in the exploratory behaviour of rats and in their sensitivity to the convulsant effects of lidocaine.

Lesion of dopaminergic terminals in the amygdala produces enhanced locomotor response to D-amphetamine and opposite changes in dopaminergic activity in prefrontal cortex and nucleus accumbens

In a previous study using differential pulse voltammetry we demonstrated an interaction between dopaminergic activity in the amygdala and the nucleus accumbens. In the present study, by post-mortem biochemical measurements, we showed that bilateral 6-OHDA lesions of DA innervation of the amygdala leads to an increase in DA activity in the nucleus accumbens (DOPAC/DA ratio +24%) and a reduction (DOPAC/DA ratio -40%) in the prefrontal cortex. In addition, after these lesions in the amygdala, there was an increased behavioral sensitivity to D-amphetamine, demonstrated by enhanced locomotor activity. Increased understanding of the interregulations between dopaminergic activity in forebrain structures may help explain forebrain functions and/or dysfunctions.

Locomotor behavior following kindling in three different brain sites

Spontaneous and drug-induced interictal and post-ictal locomotor behavior of rats was investigated following electrical 'kindling' of different limbic structures at 3 brain sites which differ in the relative amount of innervation from dopamine cells of the ventral tegmentum: nucleus accumbens (N.Acc.), amygdala (AMYG), and dorsal hippocampus (DHPC). Kindling produced decreases in spontaneous post-ictal locomotion that did not appear to depend on the site of stimulation, but produced region specific attenuations in spontaneous interictal behavior as well as amphetamine-induced interictal and post-ictal responses. The most dramatic decreases were seen in N.Acc. kindled animals and the least dramatic were seen in rats kindled via DHPC. These data suggest that the mesolimbic dopamine system may participate in the changes in locomotion seen following kindled seizures, and may also provide a model for the study of human post-ictal and interictal behavior.