Ventricular dilation over several weeks following induction of excitotoxic (systemic lithium/pilocarpine) lesions: potential role of damage to the substantia nigra reticulata

Are morphologic and functional consequences of status epilepticus in infant rats progressive?

The present study examined whether status epilepticus (SE) induced by LiCl-pilocarpine in immature rats (postnatal day [P]12) interferes with normal development; leads to progressive epileptogenesis, or cognitive decline and to pathology similar to that seen in human temporal lobe epilepsy. We correlated the extent of pathologic changes with the severity of functional alterations or epilepsy. SE-induced changes were compared with those of rats with SE induced at P25. Animals of both ages were exposed to a battery of behavioral tests for up to 3months after SE. Rats with SE at P12 showed mild retardation of psychomotor development and delayed habituation, whereas rats with SE at P25 showed no habituation. Assessment in adulthood using the Morris water maze test revealed that SE at both P12 and P25 led to cognitive impairment and that the severity of the impairment increased with age. A handling test revealed increased aggression in rats with SE at P25, but not in rats with SE at P12. Epilepsy was diagnosed with continuous video-electroencephalographic (EEG) monitoring for up to 7d. P25 rats were monitored at 5months after SE and seizures were detected in 83.3% of animals. P12 animals were divided into two groups and monitored at 5 or 7months after SE. Both the severity and incidence of spontaneous recurrent seizures tended to progress with time, and their incidence increased from 50% to 87.5% at 5 and 7months, respectively. Morphometric analysis and stereologic assessment of hilar neurons performed after video-EEG monitoring revealed atrophy of temporal brain structures, enlargement of lateral ventricles, and loss of hilar neurons in both age groups. In P12 rats, morphologic damage also tended to progress over time. Performance of animals in the Morris water maze correlated with the severity of damage, but not with seizure parameters.

A systematic review of existing data on long-term lithium therapy: neuroprotective or neurotoxic?

Lithium is an efficacious agent for the treatment of bipolar disorder, but it is unclear to what extent its long-term use may result in neuroprotective or toxic consequences. Medline was searched with the combination of the word 'Lithium' plus key words that referred to every possible effect on the central nervous system. The papers were further classified into those supporting a neuroprotective effect, those in favour of a neurotoxic effect and those that were neutral. The papers were classified into research in humans, animal and in-vitro research, case reports, and review/opinion articles. Finally, the Natural Standard evidence-based validated grading rationale was used to validate the data. The Medline search returned 970 papers up to February 2006. Inspection of the abstracts supplied 214 papers for further reviewing. Eighty-nine papers supported the neuroprotective effect (6 human research, 58 animal/in vitro, 0 case reports, 25 review/opinion articles). A total of 116 papers supported the neurotoxic effect (17 human research, 23 animal/in vitro, 60 case reports, 16 review/opinion articles). Nine papers supported no hypothesis (5 human research, 3 animal/in vitro, 0 case reports, 1 review/opinion articles). Overall, the grading suggests that the data concerning the effect of lithium therapy is that of level C, that is 'unclear or conflicting scientific evidence' since there is conflicting evidence from uncontrolled non-randomized studies accompanied by conflicting evidence from animal and basic science studies. Although more papers are in favour of the toxic effect, the great difference in the type of papers that support either hypothesis, along with publication bias and methodological issues make conclusions difficult. Lithium remains the 'gold standard' for the prophylaxis of bipolar illness, however, our review suggests that there is a rare possibility of a neurotoxic effect in real-life clinical practice even in closely monitored patients with 'therapeutic' lithium plasma levels. It is desirable to keep lithium blood levels as low as feasible with prophylaxis.

The brain matrix and multifocal brain damage following a single injection of ketamine in young adult rats: conspicuous changes in old age

Male rats were seized with lithium and pilocarpine and then injected within 30 min. with either acepromazine or ketamine. These rats as well as age-matched normal rats were observed daily for one year. The rats which had received the ketamine after the seizures were significantly heavier than either the normal rats or the other group of seized rats. The bulk of this increased weight was due to the marked increase in white, extremely dense adipose tissue. Compared to the acepromazine-treated rats, the ketamine-treated rats did not exhibit spontaneous seizures and exhibited cerebral widths comparable to normal rats. These results suggest that the multifocal, graded neuronal loss associated with this seizure model may allow other "configurations" to emerge that can support normal behaviors as well as new characteristics.

Normal spatial memory following postseizure treatment with ketamine: selective damage attenuates memory deficits in brain-damaged rodents

Within 30 min after the initiation of status epilepticus (SE) by lithium and pilocarpine, rats were injected with either acepromazine or ketamine. Compared to the rats that had received the acepromazine, the group that had received the ketamine displayed more accurate spatial memory. Their scores did not differ significantly from normal (non-seized) controls. Although the ketamine treatment did not significantly change the amount of neuronal loss within about 100 Paxinos and Watson structures, it was neuroprotective for several structures within the thalamus and portions of the temporal and parietal cortices. Ketamine-treated rats, however, displayed markedly more damage within the entorhinal cortices and amygdalohippocampal area.

Temporal changes in neuronal dropout following inductions of lithium/pilocarpine seizures in the rat

Estimates of neuronal dropout for approximately 100 structures as defined by Paxinos-Watson were completed for brains of male Wistar albino rats between 1 and 50 days after status epilepticus was evoked by a single systemic injection of lithium and pilocarpine. Sample estimates of neuronal loss were strongly correlated with direct measures of cell density. The most extensive immediate damage occurred within the substantia nigra reticulata, CA1 field of the hippocampus, the piriform cortex and the reuniens and paratenial nuclei of the thalamus. Neuronal dropout continued in many other structures over a 50-day period. Structures that showed the greatest 2-deoxyglucose (2-DG) uptake during discrete seizures and waxing and waning seizures within the early stages of status epilepticus but the least 2-DG uptake at the time of late continuous spiking and fast spiking with pauses [Neuroscience 64 (1995) 1057, 1075] exhibited the most neuronal dropout. Relationships between the delay of injection of acepromazine (which facilitated survival) and the amount of damage suggested that the source of the process that results in permanent brain damage may originate within the region of the piriform cortices and its subcortices.