Distinct models of induced hyperactivity in zebrafish larvae.

The analysis of behavioural hyperactivity can provide insights into how perturbations in normal activity may be linked to the altered function of the nervous system and possibly the symptoms of disease. As a small vertebrate zebrafish have numerous experimental advantages that are making them a powerful model for these types of studies. While the majority of behavioural studies have focused on adult zebrafish, it has become apparent that larvae can also display complex stereotypical patterns of behaviour. Here we have used three compounds (pentylenetetrazole (PTZ), aconitine and 4-aminopyridine) that have different neuronal targets (GABA, sodium and potassium channels), to induce distinct patterns of hyperactivity in larvae. Our studies have revealed that each compound produces a number of distinct concentration-dependent activity patterns. This work has shown for the first time that at sub-convulsive concentrations, PTZ can reverse the normal behavioural response to alternating periods of light and dark in zebrafish larvae. It also appears that both PTZ and 4-aminopyridine produce distinct changes in the normal startle response patterns immediately following light/dark transitions that may be the result of an elevation in stress/anxiety. Aconitine produces a general elevation in activity that eliminates the normal response to light and dark. In addition to differences in the patterns of behaviour each compound also produces a unique pattern of c-fos (an immediate early gene) expression in the brain. While more work is required to make direct links between region specific neuronal activity and individual behaviours, these models provide a framework with which to study and compare mechanistically different types of inducible behaviours.