Amygdaloid lesion increases the toxicity of intrahippocampal kainic acid injection and reduces the late occurrence of spontaneous recurrent seizures in rats

Spontaneous recurrent seizures (SRS) following intrahippocampal kainic acid (KA) injection have been described in a previous paper from our laboratory. The SRSs are clinically similar to the seizures induced by kindling the amygdala and we suggested that the amygdala plays a role in initiating the SRSs. Accordingly, the present paper examines the effect of amygdaloid lesions on intrahippocampal KA-treated rats. There were short- and long-term effects. (1) Short-term: the toxicity of KA was increased in lesioned animals. Status epilepticus followed by death of the animals was evoked with half of the dose required to cause the same effect in intact rats. Moreover, a gross haematuria was encountered 6-12 h after KA injection. This was not observed in non-lesioned rats even following the highest KA doses. (2) Long-term: amygdaloid lesions delayed the occurrence of the SRSs, reduced their incidence and modified their expression. In lesioned animals seizures began with a period of tonic immobility with no sign of the masticatory movements seen in intact animals. Histological examination of the KA-induced lesions did not show any major differences between lesioned and intact animals. It is suggested that the short-term effects are due to an unspecific effect on homeostatic mechanisms, whereas the long-term ones reflect a specific involvement of the amygdala in the late appearing seizures.     

Altered GABAergic effects on kainic acid-induced seizures in the presence of hippocampal sclerosis in rats

Although deficient inhibitory action of GABAergic neurons is frequently implicated in the pathogenesis of epileptic seizures, their exact contribution to the epileptogenicity is still controversial. In the present study, we investigated the effects of GABAergic action on kainic acid (KA)-induced hippocampal seizure in rats with or without hippocampal sclerosis (HS). HS was produced by pretreatment of KA (12 mg/kg i.p.) 3 weeks prior to induction of acute KA seizure (8 mg/kg i.p.). After development of epileptiform activity in the hippocampus, either muscimol (50 ng/microliters, 1.0 microliter) or vehicle (phosphate buffer solution, 1.0 microliter) was applied locally in the left dorsal hippocampus through a cannula and electrobehavioral observation was performed continuously for 6 h. The seizures were divided into four stages according to their severity. 7 days after the induction of acute seizure, the rats were sacrificed and subjected to histological examinations. In the rats without HS, muscimol reduced the seizure severity as well as neuronal damage, whereas muscimol facilitated the severity of both indicators in the presence of HS. Muscimol accelerated the propagation of epileptiform activity and the onset of more advanced seizure stages regardless of presence or absence of HS. Our study suggest that the GABAa function has dual effects on the final severity of KA-induced seizure depending on the presence or absence of HS and that it accelerates the rate of seizure development in either condition. The altered GABAa function in the presence of HS would probably modify seizure activity.     

Multiple kainic acid seizures in the immature and adult brain: ictal manifestations and long-term effects on learning and memory

PURPOSE: While there is increasing evidence that the adverse effects of prolonged seizures are less pronounced in the immature than in the mature brain, there have been few investigations of the long-term effects of recurrent seizures during development. This study examined the effects of multiple administrations of the convulsant kainic acid (KA) on seizure characteristics and spatial learning as a function of brain development. METHODS: To determine the long-term effects of serial KA seizures during ontogeny, saline or convulsant doses of KA were given intraperitoneally 4 times, at 2-day intervals. Immature rats were given KA on P20, P22, P24 and P26; adult rats got KA on P60, P62, P64 and P66. Ictal characteristics and EEGs were recorded. To examine the effects of multiple KA seizures on the retention of spatial learning, water maze testing was performed before (immature group: from P16-19, adult group: from P56-P59) and after (immature: from P60-P63, adult: from P100-P103) KA injections. Finally, histology was performed to compare KA-induced damage at each age. RESULTS: In immature animals, serial KA administration resulted in seizures with a progressively longer onset latency and decreased severity. In contrast, KA serially administered to adult rats caused severe seizures after each of the 4 injections. In immature rats, epileptiform EEG changes were most prominent after the first KA injection, whereas in adults, prolonged paroxysmal EEG patterns were seen after all 4 KA injections. Before KA, both rat pups and adults acquired place learning in the water maze. One month after the final KA injection, there was no deficit in spatial learning retention in the immature group, whereas the adult group had profound impairment compared to age-matched, saline-injected controls. Histology revealed no lesions in immature rats treated multiple times with KA but profound cell loss in hippocampal fields CA4, CA3 and CA1 in rats treated serially with KA as adults. CONCLUSIONS: Previous studies have shown that a single KA injection causes prolonged status epilepticus (which persists for several hours), leading to severe histologic and behavioral sequelae in adult rats but not in pups. Our study extends those findings, demonstrating that immature rats are spared the cognitive and pathological sequelae of multiple injections of convulsant doses of KA as well.     

Vulnerability and plasticity of the GABA system in the pilocarpine model of spontaneous recurrent seizures

Several similarities exist between the alterations observed in the chronic pilocarpine model of recurrent seizures in the rat and those found in human temporal lobe epilepsy. The present studies are focused on changes in the GABA system in this model. Following the initial pilocarpine-induced seizures, a substantial loss of glutamic acid decarboxylase (GAD) mRNA-containing neurons has been found in the hilus of the dentate gyrus (Obenaus et al., J. Neurosci., 13 (1993) 4470-4485), and, recently, a loss of GAD mRNA-labeled neurons has also been found in stratum oriens of CA1. Yet numerous other GABA neurons remain within the hippocampal formation, and there appear to be multiple compensatory changes in these neurons. Labeling for GAD65 mRNA and associated protein is substantially increased in the remaining GABA neurons at 2-4 months after the initial seizure episode. Such increased labeling suggests that the remaining GABA neurons are part of a functional circuit and may be responding to the need for increased activity. Alterations also occur in at least one subunit of the GABA-A receptor. Labeling for the alpha(5) subunit mRNA is substantially decreased in CA1 and CA2 of pilocarpine-treated rats during the chronic, seizure-prone period. These findings emphasize the complexity of changes in the GABA system and indicate a need for evaluating the functional consequences of each of the changes. The initial loss of specific groups of GABA neurons could be a critical first step in the gradual development of epileptiform activity. While many of the subsequent changes in the GABA system may be considered to be compensatory, significant deficits of GABAergic function could remain.     

Cyclic withdrawal from endogenous and exogenous progesterone increases kainic acid and perforant pathway induced seizures

Antiseizure effects of progesterone (P) and its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha, 5alpha-THP) were investigated following continuous vs. discontinuous P exposure. In Experiments 1, 32 cycling Long-Evans rats were administered kainic acid (32 mg/kg SC), ictal behavior was examined, and plasma 3alpha,5alpha-THP levels were measured by radioimmunoassay. Proestrus/estrus rats showed less ictal activity and had elevated 3alpha,5alpha-THP levels prior to kainic acid compared to diestrus/metestrus subjects. In Experiment 2, 49 ovariectomized (ovx) rats were SC injected with estradiol benzoate (EB; 10 microg) and P (500 microg), to mimic estrus, or sesame oil vehicle (0.2 cc); all subjects were administered kainic acid. Rats tested with EB+P showed a reduced mean duration of full seizures and increased 3alpha,5alpha-THP, whereas those tested 24 h following EB+P had more tonic clonic seizures and lower 3alpha,5alpha-THP concentrations, comparable to ovx control animals. In Experiment 3, 49 ovx rats were stereotaxically implanted with bipolar electrodes into the perforant pathway. Prior to perforant pathway stimulation, rats received cholesterol or EB+P capsules for 1 month, continuously or intermittently. Irrespective of continuous or intermittent EB+P, the presence of progestins at the time of perforant pathway stimulation reduced partial seizure activity. Continuous EB+P capsules resulted in increased 3alpha,5alpha-THP levels compared to all other conditions, and less damage in the hilus of the hippocampus, compared to intermittent EB+P. These data confirm that P and 3alpha,5alpha-THP have antiseizure effects, and further suggest that repeated cycles of endogenous or exogenous P and/or 3alpha,5alpha-THP withdrawal influences seizure threshold and/or hippocampal integrity.     

Electrocortical desynchronization after microinfusion of kainic acid into the locus coeruleus in rats

CD-1, a genetically-engineered CHO cell line, was cultivated with a Biosilon microcarrier culture system. We successfully cultivated CD-1 cells to a very high density (over 1 x 10(7) cells/ml). Prourokinase was stably secreted at about 180 IU/10(6) cells/24 h. Experiments showed that CD-1 cells growing on Biosilon microcarriers were able to spontaneously release from the microcarriers, then reattach and proliferate on fresh microcarriers. This makes it very easy to scale up production. The microcarriers could be reused several times without affecting adhesion, proliferation and prourokinase secretion. With CM-PECC membrane radial flow chromatography and MPG chromatography, the prourokinase in conditioned medium could be purified to a specific activity of 1 x 10(5) IU/mg of protein. The purification factor was about 600 fold, and approximately 90% of the biological activity was recovered.     

Prolonged expression of zinc finger immediate-early gene mRNAs and decreased protein synthesis following kainic acid induced seizures

STUDY DESIGN: A high-resolution strain measurement technique was applied to axially loaded parasagittal sections from thoracic spinal segments. OBJECTIVES: To establish a new experimental technique, develop data analysis procedures, characterize intrasample shear strain distributions, and measure intersample variability within a group of morphologically diverse samples. SUMMARY OF BACKGROUND DATA: Compression of intact vertebral bodies yields structural stiffness and strength, but not strain patterns within the trabecular bone. Finite element models yield trabecular strains but require uncertain boundary conditions and material properties. METHODS: Six spinal segments (T8-T10) were sliced in parasagittal sections 6-mm thick. Axial compression was applied in 25-N increments up to sample failure, then the load was removed. Contact radiographs of the samples were made at each loading level. Strain distributions within the central vertebral body were measured from the contact radiographs by an image correlation procedure. RESULTS: Intrasample shear strain probability distributions were log-normal at all load levels. Shear strains were concentrated directly inferior to the superior end-plate and adjacent to the anterior cortex, in regions where fractures are commonly seen clinically. Load removal restored overall sample shape, but measurable residual strains remained. CONCLUSIONS: This experimental model is a suitable means of studying low-energy vertebral fractures. The methods of data interpretation are consistent and reliable, and strain patterns correlate with clinical fracture patterns. Quantification of intersample variability provides guidelines for the design of future experiments, and the strain patterns form a basis for validation of finite element models. The results imply that strain uniformity is an important criterion in assessing risk of vertebral failure.     

Anticonvulsant effects of dipotassium clorazepate on hippocampal kindled seizures in rats

OBJECTIVE: To determine the reliability of some commonly used outcome measures in patients with rheumatoid arthritis. METHODS: We studied 22 consecutive patients with rheumatoid arthritis enrolled in a clinical trial in a tertiary care center. The study design consisted of a test-retest, in which the same rheumatologist evaluated all of the patients twice, with an interval between evaluations of 90 to 120 minutes. Statistical analysis of the data consisted of calculation of the weighted Kappa (kw) and the intraclass correlation coefficient (ICC). RESULTS: For the Ritchie articular index, kappa w = 0.83, ICC = 0.49, p < 0.0001; tender joint count, kappa w = 0.82, ICC = 0.49, p < 0.0001; physician's global assessment, kappa w = 0.79, ICC = 0.48, p < 0.0001; disease activity score, kappa w = 0.79, ICC = 0.49, p < 0.0001; utilities, kappa w = 0.71, ICC = 0.48, p < 0.0001; swollen joint count, kappa w = 0.7, ICC = 0.47, p < 0.0001; patient's global assessment, kappa w = 0.58, ICC = 0.44, p < 0.0001; pain kappa w = 0.45, ICC = 0.41, p < 0.0001. CONCLUSIONS: The reliability of most of the outcome measures was good. It was higher for those measurements evaluated by a rheumatologist and for the composite indexes. Those requiring patient participation need to be improved.     

Endocrine factors associated with recurrent spontaneous abortion

The role of endocrine factors as a cause of recurrent spontaneous abortion is controversial. Diabetes mellitus and thyroid disease do not represent a significant risk factor for recurrent pregnancy loss. Luteal-phase defect has been questioned because there are no accurate methods for diagnosis and no convincing evidence of correction with treatment exists. The corpus luteum is an unusual endocrine gland, highly diverse in function and important for successful reproduction in all mammalian species. Much controversy exists about the luteal function in humans and how defects in luteal function affects reproduction. Disagreement has been due to lack of accurate diagnosis and controlled studies to determine whether correction of the luteal-phase defect is worthwhile when treating female reproductive problems. The donor egg recipient model from assisted reproductive technology programs has shown that corpus luteum function can be replaced by estrogen and progesterone administration. The mechanism by which these steroids stimulate a uterus to be receptive to implantation of the embryo is not known. Several proteins produced by the endometrium are candidate markers for uterine receptivity. Further work needs to be done to correlate these markers with subsequent pregnancy outcome. A noninvasive marker for uterine receptivity is ultrasonographic evaluation of the endometrium. Although the sensitivity of this test is high (100%), its specificity is low (only 20% to 60%).     

Progressive neurodegeneration after intracerebroventricular kainic acid administration in rats: implications for schizophrenia?

BACKGROUND: Intracerebroventricular (ICV) administration of kainic acid to rats produces limbic-cortical neuronal damage that has been compared to the neuropathology of schizophrenia. METHODS: Groups of adult rats were administered ICV kainic acid and then assessed for neuronal loss and the expression of proteins relevant to mechanisms of neuronal damage after one and fourteen days. Neuronal loss was assessed by two-dimensional cell counting and protein expression was assessed by immunohistochemistry. RESULTS: ICV kainic acid administration was associated with both immediate (day 1) and delayed (day 14) neuronal loss in the dorsal hippocampus. The immediate injury was largely limited to the CA3 hippocampal subfield, while the delayed injury included the CA1 subfield. Multiple mechanisms of cell death appeared to be involved in the delayed neuronal loss, as evidenced by changes in the expression of glutamate receptor subunits, heat shock protein and jun protein. CONCLUSIONS: ICV kainic acid administration to adult rats produces progressive damage to limbic-cortical neurons, involving both fast and slow mechanisms of cell death. Given the evidence for clinical deterioration, cognitive deficits and hippocampal neuropathy in some cases of schizophrenia, this animal model may be relevant for hypotheses regarding mechanisms of neurodegeneration in that disorder.     

Influence of ZnCl2 pretreatment on behavioral and histological responses to kainic acid in rats

Kainic acid evokes behavioral convulsions and causes lesions in hippocampal pyramidal cell layers in rats. The effects of ZnCl2 pretreatments on these events were examined. Rats were given ZnCl2 (35 mg/kg, subcutaneously (s.c.)) 15 min prior to kainic acid administration (12 mg/kg, intraperitoneally (i.p.)). Another group of animals was given an additional dose of ZnCl2 (35 mg/kg, i.p.) 24 h prior to the s.c. ZnCl2 and i.p. kainic acid. All rats that received kainic acid, whether saline controls or ZnCl2 pretreated, experienced wet dog shakes (WDS) and convulsions. No significant differences were seen between groups in number or latency of WDS or convulsions. Two days after behavioral data were collected, the brains were perfused and the extent of lesioning among hippocampal CA1 and CA3 pyramidal cells was quantified. A single dose of ZnCl2 had either no effect or a slight protective effect on cell lesioning induced by kainic acid. However, lesioning was more pronounced in animals treated twice with zinc. It is concluded that zinc, co-administered with kainic acid, augments kainate cytotoxicity when the dose and timing of zinc exposure are within a critical period.     

Development of a novel rat mutant with spontaneous limbic-like seizures

A new epileptic rat mutant with spontaneous seizures was developed by successive mating and selection from an inherited cataract rat. The procedures for developing the mutant and the symptomatology, electroencephalographic correlates, and neuropathology of the mutant are reported. It is possible that this rat stain will provide a useful animal model for human temporal lobe epilepsy. The seizures of the rat usually begin with face and head myoclonus, followed by rearing, and generalized clonic and tonic convulsions, all of which are symptomatologically the same as limbic seizures. Electrographic recording during generalized convulsive seizures demonstrated that sustained spike discharges emerged at the hippocampus and then propagated to the neocortex. Seizures occurred spontaneously without any artificial stimuli. Furthermore, external stimuli such as auditory, flashing light, or vestibular stimulations could not elicit epileptic attacks. Almost all of the male animals had generalized convulsions, mostly from 5 months after birth, and the frequency of the seizures increased with aging. Generalized convulsions developed in approximately 20% of the female rats. Microdysgenesis, such as abnormal neuronal clustering, neuronal disarrangement, or interruption of pyramidal neurons in the hippocampal formation, was found in the young rats that had not yet had generalized seizures. This microdysgenesis, which is though to be genetically programmed, was very interesting from the aspect of the relationship between structural abnormalities and epileptogenesis in this mutant. In addition to microdysgenesis, there was sprouting of mossy fibers into the inner molecular layer of the dentate gyrus in those adult rats that had repeated generalized convulsions. An increase of glial-fibrillary-acidic-protein-positive astrocytes with thickened and numerous processes, ie, astrogliosis, was also found in the cerebral cortex, amygdala region, and hippocampus of these adult animals. Judging from the characteristics of the symptomatology, electroencephalographic correlates, and neuropathology, this epileptic mutant can be expected to be a useful animal model for studying human temporal lobe epilepsy.     

Effects of a subconvulsant dose of kainic acid on afterdischarges elicited by cortical stimulation in rats

Trends in medical education include those occurring in medical practice, related with its contents, and in the educational sciences, related with methods and technics that could be employed. Trends in medical practice are related to epidemiologic, demographic and economic transitions, with the overwhelming influence of medical technology, specially molecular biology, the increasing social regulation, evidence based medicine and transdisciplinary contributions. In the field of pedagogy, trends include the acceptance of the strategic value of medical education, the importance of quality-and not only of covering, the attention to educational necessities, the recognition of the adulthood of most of the learners, the importance of its individual differences and the application of new educational technics.     

The spontaneous otitis media in rickety rats

This paper is aimed to study the incidence and hearing impairment of spontaneous otitis media in rickety rats during a longterm vitamin D deficient breeding. Thirty Sprague-Dawley rats ranged from 20 to 25-day-old were used, and vitamin D deficient rickets models were established. Another thirty rats were used as the normal control. It was found that both normal and rickety rats had the possibilities of suffering from otitis media (mainly exudative) during the two-month-breeding. The incidence of otitis media in normal rats was 5% (3 from 60 ears), while that in the rickety ones was 16.67% (10 from 60 ears). It is believed that a rickety sufferer may be in higher danger of having otitis media than the normal one.     

Polarization anatomy of a kainic acid seizure

A CD8+ cytotoxic T-cell clone that recognized HIV p24gag was isolated from an infected individual. The minimal epitope was localized to amino acids 308-316 (QASQEVKNW). Using allogeneic target cells, we found that lysis was restricted by the HLA-Cw0401 molecule. We observed that C1R cells, that express the HLA-Cw0401 allele are able to present the peptide to the cytotoxic clone, but with reduced efficiency. Other B-cell lines, that have been genotyped as HLA-Cw0401+ were unable to present the peptide to the clone, suggesting the existence of other variants of HLA-Cw0401 or a loss of cell surface expression of this molecule.     

Uteroplacental vascular involvement in recurrent spontaneous abortion

In the present study, we assessed the ability of increasing doses of intranasal calcitonin to suppress urinary deoxypyridinoline cross-link (DPD), a specific biochemical marker of bone resorption, in early postmenopausal women. Subjects consisted of 30 healthy Thai women within 5 years of postmenopause, randomly assigned to 50, 100, or 200 IU of intranasal calcitonin 5 days/week for 3 months. Calcium supplementation by calcium carbonate capsules at 750 mg of elemental calcium per day was given to all subjects. Twenty four-hour urine for DPD and creatinine assays was collected at baseline, 1 month, and 3 months after treatment. All DPD values were corrected with urinary creatinine before analyses. Data were expressed as mean +/- SEM. DPD decreased significantly 1 month after intranasal calcitonin treatment (P < 0.01). However, at 3 months, DPD increased when compared with the values at 1 month (P < 0.01), suggesting that there may be a reduction in the suppression of bone resorption after prolonged calcitonin therapy. Using a stepwise multiple regression model to address whether dosage and DPD at baseline influence the response to intranasal calcitonin, it was found that DPD suppression after intranasal calcitonin was not related to dosage but was strongly associated with baseline DPD (P < 0.0001). Suppression of bone resorption in early postmenopausal women by intranasal calcitonin is determined more by the state of bone turnover at baseline than the dosage of calcitonin.