Elsevier

Neuroscience

Volume 131, Issue 3, 2005, Pages 759-768
Neuroscience

Pentylenetetrazole induced changes in zebrafish behavior, neural activity and c-fos expression

https://doi.org/10.1016/j.neuroscience.2004.11.031Get rights and content

Abstract

Rodent seizure models have significantly contributed to our basic understanding of epilepsy. However, medically intractable forms of epilepsy persist and the fundamental mechanisms underlying this disease remain unclear. Here we show that seizures can be elicited in a simple vertebrate system e.g. zebrafish larvae (Danio rerio). Exposure to a common convulsant agent (pentylenetetrazole, PTZ) induced a stereotyped and concentration-dependent sequence of behavioral changes culminating in clonus-like convulsions. Extracellular recordings from fish optic tectum revealed ictal and interictal-like electrographic discharges after application of PTZ, which could be blocked by tetrodotoxin or glutamate receptor antagonists. Epileptiform discharges were suppressed by commonly used antiepileptic drugs, valproate and diazepam, in a concentration-dependent manner. Up-regulation of c-fos expression was also observed in CNS structures of zebrafish exposed to PTZ. Taken together, these results demonstrate that chemically-induced seizures in zebrafish exhibit behavioral, electrographic, and molecular changes that would be expected from a rodent seizure model. Therefore, zebrafish larvae represent a powerful new system to study the underlying basis of seizure generation, epilepsy and epileptogenesis.

Section snippets

Animals and maintenance

Zebrafish of the TL strain were maintained according to standard procedures (Westerfield, 1995). All experiments conformed to UCSF and AAALAC guidelines on the ethical use of animals. All animal care procedures were reviewed and approved by the UCSF Institutional Animal Care and Use Committee and were designed to minimize the number of animals used and their suffering. For all experiments zebrafish larvae were maintained in a “normal bathing medium” consisting of 0.03% Instant Ocean (Aquarium

Behavioral seizure activity in larval zebrafish

It is well established that seizures induced in rodents are associated with distinct motor behaviors (Racine, 1972). If zebrafish are to be used for epilepsy research, it is first necessary to establish and define a sequence of seizure-like behaviors. To induce seizures, PTZ (2.5–15 mM) a common convulsant agent, was added to normal bathing medium. Control experiments demonstrated that zebrafish larvae aged 7 dpf swim, infrequently, in small dart-like steps when placed in normal bathing medium.

Discussion

The key finding of this study is that PTZ, a common convulsant, reliably elicited seizures in zebrafish larvae. Previous studies demonstrated the usefulness of rodent PTZ models for AED discovery (Ferrendelli et al., 1989; Shank et al., 1994; Loscher, 2002) and analysis of seizure-generating mechanisms (Mirski and Ferrendelli, 1986; Barkai et al., 1994; Psarropoulou et al., 1994). Our observations indicate that in a simple genetically tractable vertebrate PTZ-induced seizures result in

Conclusions

Genetically tractable model systems such as the bang-sensitive Drosophila mutants have been used to study genes that modify seizure susceptibility (Pavlidis and Tanouye, 1995; Kuebler and Tanouye, 2000; Kuebler et al., 2001). These studies utilize a stimulation-induced afterdischarge model and highlight roles for membrane-bound ion channels in seizure genesis. However, the limitation of this approach is that freely behaving seizure-like activity combined with evidence of abnormal electrical

Acknowledgments

The authors thank N. M. Barbaro, D. H. Lowenstein and S. J. Pleasure for their comments on an earlier version of the manuscript. This work was supported by funds from the UCSF Basic Innovations in Science Fund, Epilepsy Foundation of American Holden Targeted Investigations Program and National Institutes of Health (joint grants to S.C.B. and H.B.).

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