Pharmacological studies with a GABA uptake inhibitor in rats with kindled seizures in the amygdala

The anticonvulsant effects of the inhibitor of the uptake of GABA, SKF 89976-A (N-[4,4-diphenyl-3-butenyl]-nipecotic acid), were investigated using the amygdala kindling seizure model in rats. The time course of activity of the racemic mixture, given orally, and the relative potencies of its d- and l-isomers, when given intraperitoneally, were tested. The drug SKF 89976-A was active, when given orally with anticonvulsant effects lasting 2-4 hr when given at 15 mg/kg, and 4-6 hr when given at 30 mg/kg. Peak inhibition of severity of seizures occurred at 1 hr after administration with an ED50 of 17.8 mg/kg. The d-isomer of SKF 89976-A was significantly more potent than the l-isomer and inhibited various parameters of kindled seizure activity in a dose-dependent manner. The l-isomer had significant effects on kindled seizures only at the largest dose (20 mg/kg). The ED50 of the d-isomer for inhibition of severity of seizures measured 0.5 hr after intraperitoneal injection, was 11.2 mg/kg and the antiseizure effects of the d-isomer lasted for 2-3 hr. Side effects of SKF 89976-A, such as sedation, abdominal muscle relaxation, rear limb splaying and ataxia, were seen at 30 mg/kg; there was a marked suppression of seizure activity with no side effects at smaller doses. The characterization of a biphasic kindled seizure allows for speculation regarding the role of GABAergic mechanisms in its pathogenesis and of the mechanism of action of SKF 89976-A.     

Subarachnoid hemorrhage due to Borrelia burgdorferi-associated vasculitis

We report the case history of a patient who suffered a subarachnoid hemorrhage (SAH) in association with early Lyme neuroborreliosis. After a tick bite, this patient developed erythema chronicum migrans and complained of stinging radicular pain in both legs. A computed tomography (CT) scan was performed because of acute headache and nuchal rigidity, which revealed an occipital SAH. Cerebrospinal fluid analysis provided further evidence of acute neuroborreliosis. Digital substraction angiography showed irregularities in the right posterior cerebral artery, which might be due to vasculitis, but no aneurysms.     

Lifetime lead intoxication: influence on the amygdaloid kindling model of epileptogenesis

The nature of amygdaloid kindled seizures was studied in adult rats which were intoxicated with lead starting in neonatal life. Lactating females were exposed to lead via the drinking water (0.25% lead acetate) and the litters were continued on this level of lead after weaning at 27 days of age. When compared to controls, levels of lead in the blood and brain were significantly higher in lead-exposed rats, both at the time of weaning as well as postkindling, beyond 150 days of age. Parameters relating to amygdaloid kindled seizures, including the rate of kindling, seizure latency and seizure threshold were not significantly different in lead-treated rats than in controls. However, duration of behavioral seizures and afterdischarges was significantly longer in rats exposed to lead. Our data suggest that, although lead intoxication starting in neonatal life does not appear to affect the susceptibility to development of amygdaloid kindled seizures, it may enhance seizure severity in this model of epileptogenesis.     

Aspects of the pentylenetetrazol kindling model of epileptogenesis in the rat

The kindling model of epileptogenesis is characterized by the induction of a persistent reduction of seizure threshold after repeated exposures of the brain to stimuli which were initially subconvulsive. We studied the ability of repeated injections of pentylenetetrazol (PTZ) to induce kindling. Subconvulsive doses of PTZ (20–25 mg/kg, i.p.) were administered to rats every 4 days for a total of 21 treatments. The convulsive response score of PTZ-treated rats remained elevated upon challenge with 22.5 mg/kg PTZ after a 3-week PTZ-free period. Studies on the mechanisms involved in PTZ-induced kindling revealed that hepatic microsomal P-450 concentrations were unchanged after chronic PTZ treatment. No significant changes in brain amino acids, including GABA and taurine, two neuroinhibitory amino acids which have been implicated in the regulation of seizure phenomena, were found in PTZ-kindled animals.     

Effects of fluoroquinolone antimicrobials alone and in conjunction with theophylline on seizures in amygdaloid kindled rats. Mechanistic and pharmacokinetic study.

The influence of three fluoroquinolone (FQ) antimicrobial drugs (ciprofloxacin (CP), norfloxacin (NF), enrofloxacin (EF)) on seizure parameters in amygdaloid kindled rats was investigated. CP and NF (100 mg/kg i.p.) did not modify seizure parameters while EF induced a decrease in seizure activity. Since clinical data indicate a seizure enhancing interaction between FQ and theophylline (THEO) we studied the influence of concurrent FQ-THEO administration in kindled rats. CP and NF, but not EF given concurrently with a non-seizure modulating dose of THEO (10 mg/kg i.p.) caused increases in seizure activity and aggressiveness in the animals. The CP-THEO induced seizure enhancement was antagonized by 2-chloroadenosine and diazepam. Pharmacokinetic studies demonstrated that THEO serum levels and elimination were not altered by concurrent CP administration. We conclude that coadministration of FQ-THEO can aggravate amygdala kindled seizures and that this aggravation may involve centrally mediated mechanisms.     

Reliable genetic identification of burnt human remains

The identification of severely burnt human remains by genetic fingerprinting is a common task in forensic routine work. In cases of extreme fire impact, only hard tissues (bones, teeth) may be left for DNA analysis. DNA extracted from burnt bone fragments may be highly degraded, making an amplification of genetic markers difficult or even impossible. Furthermore, heavily burnt bones are very prone to contamination with external DNA.We investigated whether authentic DNA profiles can be generated from human bones showing different stages of fire induced destruction (well preserved, semi-burnt, black burnt, blue–grey burnt, blue–grey–white burnt). DNA was extracted from 71 bone fragments derived from 13 individuals. Obtained genetic patterns (STRs and mtDNA sequences) were compared to the genetic pattern of the respective bodies.Our results show that the identification via DNA analysis is reliably and reproducibly possible from well preserved and semi-burnt bones. In black burnt bones the DNA was highly degraded and in some cases no nuclear DNA was left, leaving mitochondrial DNA analysis as an option. Blue–grey burnt bones lead only sporadically to authentic profiles. The investigation of blue–grey–white burnt bones barely led to reliable results.     

Molekulargenetische Identifikation von <Emphasis Type="Italic">Canidae</Emphasis> in der forensischen Praxis

The number of offences with animals as a “weapon” or as victims is steadily increasing; therefore, the establishment of molecular genetic animal-specific assays is recommended and one goal was to develop a simple genetic testing system for species determination. In addition to forensic genetic tests, biostatistical methods must be developed and validated. This article presents a case where a dog was beaten to death. Employing preliminary tests for blood determination, a self-designed restriction fragment length polymorphism (RFLP) analysis, short tandem repeat (STR) typing and subsequent biostatistical calculations using a self-developed software program, the identity of the dead dog could be proven and the animal could be linked to the potential weapon leading to the conviction of the offender.     

Selective inhibition of the Na+/H+ exchanger type 3 activates CO2/H+-sensitive medullary neurones

Hypercapnia as well as lowered intracellular pH (pH_i) increase the bioelectric activity of CO₂/H⁺-sensitive neurones (VLNcs) of the ventrolateral medulla oblongata. Here we describe that immunoreactive Na⁺/H⁺ exchanger (NHE3) is present in ventrolateral neurones from medullary organotypic cultures (obex level). To test whether VLNcs can be acidified and thereby activated by inhibition of NHE3, we used the novel high-affinity NHE3-inhibitors S1611 and S3226. Both drugs raised the firing rates of VLNcs to at least 150% of the control values, and depolarized membrane potential by up to 15 mV at concentrations (0.5–1 μmol/l) suitable for selective inhibition of NHE3. The changes in bioelectric activity strongly resembled the responses to hypercapnia (PCO₂: 60–100 mmHg). In BCECF-AM-loaded cultures a subfraction of ventrolateral VLNcs was found to be intracellularly acidified by 0.05–0.1 pH units following treatment with S1611; the time course of this acidification was similar to that evoked by hypercapnia. All drug effects were sustained and readily reversible upon washing. Non-CO₂/H⁺-responsive medullary neurones as well as hippocampal CA3 neurones were unaffected by up to 20 μmol/l S1611. It is concluded that the selective inhibition of NHE3 acidifies and activates CO₂/H⁺-sensitive neurones within the ventrolateral medulla oblongata. Received: 12 February 1999 / Received after revision and accepted: 15 April 1999     

Regulation of activin A synthesis in microglial cells: Pathophysiological implications for bacterial meningitis

Previous studies have shown that activin A, a neuroprotective cytokine and dimeric polypeptide composed of two βA subunits, is elevated in the cerebrospinal fluid of patients suffering from bacterial meningitis. In this study, to elucidate further the functional significance and pathophysiological implications of these findings, we demonstrated that microglial cells are not only the source but also the target cells of activin A in the central nervous system: immunohistochemistry and RT‐PCR revealed expression of activin subunit βA mRNA as well as activin receptor type I and type II mRNA in rat microglia in vitro. Further studies showed that activin enhances microglial proliferation and decreases the γ‐interferon‐induced synthesis of nitric oxide, one of several microglial mediators involved in the inflammatory response in microglia activation. Furthermore, quantitative RT‐PCR, Western blotting, and ELISA showed an inhibitory effect of activin on inducible nitric oxide synthase, tumor necrosis factor‐α, interleukin‐6, and interleukin‐1β gene and protein levels after lipopolysaccharide treatment. We suggest that the increased synthesis of activin A is directly involved, via influence on microglia cell functions, in the modulation of the inflammatory response in bacterial meningitis. © 2009 Wiley‐Liss, Inc.