Effect of heat exposure on aminophylline-induced convulsions in mice

Identifying and Understanding Seizure Liability in Drug Development

Seizures are complex electrophysiological disturbances affecting one or more populations of brain neurons. Seizures following test article (TA) exposure pose significant challenges in drug development. This paper considers the diverse neurological manifestations, mechanisms, and functional and structural assessments needed to investigate TA-related seizure liabilities, with a particular focus on nonclinical species. Accurate discrimination of seizures from convulsions (irregular involuntary body and/or limb movements) and the nuanced presentation of different seizure types (partial vs. general) and phases (prodromal, ictal, and postictal) are essential for discerning their clinical implications. In nonclinical safety testing, the most direct evaluation method to confirm existence of seizures is electroencephalography (EEG) while clinical endpoints (e.g., functional observational batteries [FOB], comprehensive neurological examinations) and neuropathological findings (e.g., neuronal necrosis in tissue sections, raised biomarker levels in cerebrospinal fluid or serum) can indicate a seizure liability and provide additional guidance to identify the origin, frequency, and severity of seizures needed to align nonclinical effects with clinical relevance. In general, the regulatory perspective is that seizures identified in nonclinical species as well as potential risk management strategies (e.g., safety margin considerations, dosing paradigms, and clinical monitoring) translate effectively for purposes of clinical risk assessment.

Zebrafish on a chip: a novel platform for real-time monitoring of drug-induced developmental toxicity

Pharmaceutical safety testing requires a cheap, fast and highly efficient platform for real-time evaluation of drug toxicity and secondary effects. In this study, we have developed a microfluidic system for phenotype-based evaluation of toxic and teratogenic effects of drugs using zebrafish (Danio rerio) embryos and larvae as the model organism. The microfluidic chip is composed of two independent functional units, enabling the assessment of zebrafish embryos and larvae. Each unit consists of a fluidic concentration gradient generator and a row of seven culture chambers to accommodate zebrafish. To test the accuracy of this new chip platform, we examined the toxicity and teratogenicity of an anti-asthmatic agent-aminophylline (Apl) on 210 embryos and 210 larvae (10 individuals per chamber). The effect of Apl on zebrafish embryonic development was quantitatively assessed by recording a series of physiological indicators such as heart rate, survival rate, body length and hatch rate. Most importantly, a new index called clonic convulsion rate, combined with mortality was used to evaluate the toxicities of Apl on zebrafish larvae. We found that Apl can induce deformity and cardiovascular toxicity in both zebrafish embryos and larvae. This microdevice is a multiplexed testing apparatus that allows for the examination of indexes beyond toxicity and teratogenicity at the sub-organ and cellular levels and provides a potentially cost-effective and rapid pharmaceutical safety assessment tool.

Effect of Extremely Low Frequency Electromagnetic Field and GABAA Receptors on Serum Testosterone Level of Male Rats

BACKGROUND

GABA can influence the steroidogenesis in peripheral and central nervoussystems.

OBJECTIVES

The present study investigates the interactive effect of GABAA receptors and extremely low frequency electromagnetic field on serum testosterone level of male rats.

PATIENTS AND METHODS

Fifty adult male rats were randomly assigned into 10 groups. Groups 2, 4, 6, 8, and 10 were exposed to ELF-EMF for 30 days 8hrs per day; while, the remaining groups (1, 3, 5, 7, and 9) were sham exposed animals. At the end of the experiment, animals in groups 1 and 2 received normal saline; while, animals in groups 3 and 4 were treated with 1 mg/kg of bicuculline methiodide, and for animals of groups 5 and 6,3 mg/kg of bicuculline was injected. Animals of groups 7 and 8 were treated with 0.5 mg/kg of muscimol hydrobromide and rats in groups 9 and 10 received 2 mg/kg muscimol hydrobromide. About forty minutes after the injection, blood samples were collected and serum testosterone level was assayed using RIA.

RESULTS

Administration of muscimol hydrobromide at both doses to sham exposed rats significantly decreased serum testosterone level as compared to sham exposed animals which received saline. Administration of bicuculline methiodide without exposure to ELF-EMF, had no significant effect on testosterone level as compared to group 1. Serum testosterone levels of rats in different groups, exposed to ELF-EMF were statistically the same. Moreover, serum testosterone of exposed and sham exposed rats in each treatment showed no significant difference.

CONCLUSIONS

No interactivity is present in modulatory effects of GABAA receptors and ELF-EMFs on serum testosterone of male rats.