Locomotor activity Drosophila

Although circadian oscillators are found in many tissues, only two rhythmic outputs have been identified in Drosophila adults. The most extensively studied rhythmic output is locomotor activity. A group of 4—5 sLN s in each hemisphere of the brain is both necessary and sufficient to drive robust activity rhythms (Frisch et al 1994, Renn et al 1999). The other rhythmic output is in olfactory responses, which are measured using an assay of odour-induced... 

Connolly (1966) has selectively bred Drosophila for level of spontaneous locomotor activity. The directional selection imposed resulted in an extremely inactive line and a highly active one. It has been established by Connolly (1967) that the principal phenotypic difference between the strains was spontaneous activity and not reactivity to environmental stimuli. The genetic system involved in the expression of phenotype is polygenic and the character has a heritability of 0.51 + 0.10. The concentrations of biogenic amines were assayed in the two selected strains and in an unselected, control strain (Tunnicliff et al., 1969). Dopamine concentrations were maximal in the inactive line and lowest in the active, the control strain having an intermediate dopamine... 

Fig. 3. Effects on increasing the concentration of y-hydroxybutyric acid in the nutrient medium on the spontaneous locomotor activity of Drosophila melanogaster. The active strain (A—A) exhibited spontaneous activity which decreased in inverse proportion to the amount of drug in the medium. The unselected control strain ( — ) was not so affected over the dose range used. Each point is the mean activity of 20 flies at each drug condition, s.e.m. s are indicated by bars.

Connolly, K. (1966) Locomotor activity in Drosophila. II. Selection for active and inactive strains. Anim. Behav., 14,444-449. 

Connolly, K., Tunnicliff, G. and Rick, J. T. (1971) The effects of gamma-hydroxybutyric acid on spontaneous locomotor activity and dopamine level in a selected strain of Drosophila melanogaster. Comp. Biochem. Physiol., 408, 321-326. 

Fig. 11.3. Circadian rhythm of locomotor activity in the fly Drosophila (Konopka Benzer, 1971). Shown, from top to bottom, are the rhythms for the normal fly, the arrhythmic mutant, and the pet and per mutants. The rhythms are monitored in constant infrared light by an event recorder. Records read from left to right each successive interval is replotted to the right of the preceding one.

Fig. 11.4. Temperature dependence of the rhythm of locomotor activity in Drosophila (Konopka et ai, 1989). Shown are the temperature-compensated curve for the wild type, and the noncompensated variation for the per and per mutants.

Another important study (Zeng et al., 1994) demonstrated that the overexpression of PER in the Drosophila eyes represses per transcription and suppresses circadian rhythmicity in these cells, without affecting circadian PER oscillations in other per-expressing cells in the brain, or the circadian rhythm in locomotor activity. This work also shows that the action of PER on transcription is intracellular, and suggests that each per-expressing cell contains an autonomous oscillator of which the per feedback loop is a component (Zeng et al., 1994). 

To confirm t ie hits from the primary screen, it is critical to develop secondary or validation assays. The assay that we used for this protocol is behavior-based circadian assay that measures the locomotor activity of Drosophila. Locomotor movement of Drosophila can be measured with special apparatuses. These devices are housed in environmentally controlled incubators located in a darkroom and use a beam of infrared light to record the locomotor activity of individual flies contained inside small mbes. When measured over a week, Drosophila exhibit daily cycles of activity and inactivity, a behavioral rhythm that is governed by the animal s endogenous circadian system. 

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