In behavioural research, internal states are measured through novelty responses. The way an animal responds to novel stimuli in the environment depends on its internal state (e.g., motivational drives), as determined by interacting neural and neurotransmitter systems (Horstick, Mueller, and Burgess, 2018). Animals that have recently had a stressful experience, for example, are more likely to be wary of novel stimuli.
Larval zebrafish (Danio rerio) are highly sensitive to light (Burgess and Granato, 2007). They display regular rates of discontinuous motion while swimming under even illumination, and can react to a sudden change in light with stereotyped locomotion alterations. This makes them ideal for studies of internal states (De Marco et al., 2016) and behavioural screens. The Zantiks MWP_vb unit allows measuring the activity of multiple larvae and control light of varying power and wavelength.
Experimental set up
Larval zebrafish are placed individually in each well of a 6, 12, 24 48 or 96 well plate.
The multiwell plate with larvae is inserted into the chamber of the Zantiks MWP_vb unit. The script can be written to control single or multiple square pulses of light, of varying length and known power and wavelength, as well as control the temperature of the medium inside the wells. Locomotor activity of each larva (measured in arbitrary units or as swum distance) is measured and written to a data file at the frequency required by the observer.
Exemplary video (speed, 8x) of zebrafish larvae in a 24-well plate during two consecutive 120 s square pulses of light (intertrial interval, 120 s).
De Marco, R.J., Thiemann, T., Groneberg, A.H., Herget, U., and Ryu, S (2016). Optogenetically enhanced activity of pituitary corticotroph cells post stress onset causes rapid organizing effects on behaviour. Nat. Commun. 7, 12620 DOI: 10.1038/ncomms12620