Conditioning to ethanol in the fruit fly-a study using an inhibitor of ADH.

To identify processes involved in the choice of ethanol by adult Drosophila, flies homozygous Adh(F), reared in the absence of alcohol were placed in contact with: a) an ethanol-free medium, b) a medium containing ethanol, c) a medium supplemented with 4-methylpyrazole (4-MP, an inhibitor of the ADH pathway), d) a medium containing ethanol and 4-MP. The choice of ethanol over a medium without ethanol was evaluated by measuring the duration of extension of the proboscis of the flies in each of the media. A slight preference for the ethanol-supplemented medium was observed in the naive flies, which was enhanced by previous exposure to ethanol. Exposure to ethanol and 4-MP, however, led to an avoidance of ethanol. There was a reduction in ADH activity on treatment of the flies with 4-MP, and signs of malaise (reduced locomotor activity, loss of balance) were observed in the flies who ingested both ethanol and inhibitor. We concluded that the preference for ethanol stems from an associative learning related to ethanol utilization. Inhibition of enzymes of ADH pathway led to a conditioned aversion due to disturbance of ethanol metabolism giving rise to malaise.

Is food recognition in an unfamiliar environment a long-term effect of stimulus or local enhancement? A study in the juvenile canary.

The processes involved in the social transmission of recognition and consumption of hemp seeds were investigated in juvenile canaries (Serinus canarius). The combined influences of observation of a parent feeding, presence of parent and accessibility of seeds on future seed consumption were investigated in six experimental conditions (each employing 15 individuals). We found that: (i) local enhancement and social facilitation were not required for social transmission, (ii) transmission took place if the juvenile observed seeds in the vicinity of the parent, whether the seeds were accessible or not (mere presence effect). Accessibility, however, did favour transmission; (iii) observation of a parent feeding was sufficient for social transmission of information even if the seeds were not available during interactions with the adult. The juvenile thus appeared to recognise seeds by stimulus enhancement, and this recognition was maintained in both space and time. The various interactions with adults enabled the juveniles to identify edible objects even in an unfamiliar environment.