Un-filtered recordings from insect taste sensilla

140

143

SUMMARY The hormonal regulation of feeding behaviour is well known in vertebrates,whereas it remains poorly understood in insects. Here, we report that the takeout gene is an essential component of nutritional homeostasis in Drosophila. takeout encodes a putative juvenile hormone (JH)binding protein and has been described as a link between circadian rhythm and feeding behaviour. However, the physiological role of takeout and its putative link to JH remain unknown. In this study, we show that takeout (to1) flies failed to adapt their food intake according to food availability and that most defects could be genetically rescued. When food is abundant, to1 are hyperphagic, yielding to hypertrophy of the fat body. When food reappears after a starvation period, to1 flies do not increase their food intake as much as wild-type flies. This defect in food intake regulation is partly based on the action of Takeout on taste neurons, because the sensitivity of to1 gustatory neurons to sugars does not increase after starvation, as in wild-type neurons. This lack of regulation is also evident at the locomotor activity, which normally increases during starvation, a behaviour related to food foraging. In addition, to1 flies lack sexual dimorphism of locomotor activity,which has previously been linked to the JH circulating level. Moreover,application of the JH analog methoprene rescues the phenotype. These results suggest that takeout plays a central role as a feeding regulator and may act by modulating the circulating JH level.

Section: Electrophysiological Recording Of the Taste Neuronsmentioning

confidence: 99%

Regulation of feeding behaviour and locomotor activity bytakeoutinDrosophila

Meunier

Belgacem

Martin

2007

140

143

“…We recorded extracellular alternating current signals with the Tasteprobe amplifier system (Syntech, Hilversum, The Netherlands) (Marion-Poll and Van der Pers, 1996). We preamplified each recording 10ϫ, ran it through a band-pass filter set at 100-1200·Hz, fed it into a computer through a 16-bit analog-to-digital converter board, and then analyzed it offline with Autospike software (Syntech).…”

Section: Electrophysiological Recordingsmentioning

confidence: 99%

The hungry caterpillar: an analysis of how carbohydrates stimulate feeding inManduca sexta

Glendinning

Jerud

Reinherz

2007

SUMMARY In most insects, the taste of carbohydrates stimulates an immediate appetitive response. The caterpillar of Manduca sexta is an exception to this general pattern. Despite eliciting a strong peripheral gustatory response, high concentrations of carbohydrates (e.g. glucose or inositol)stimulate the same intensity of biting as water during 2-min tests. We suspected that the lack of feeding stimulation reflected the fact that prior studies used single carbohydrates (e.g. sucrose), which M. sextawould rarely encounter in its host plants. We hypothesized that the feeding control system of M. sexta responds selectively to carbohydrate mixtures. To test this hypothesis, we ran three experiments. First, we stimulated the two taste sensilla that respond to carbohydrates (the lateral and medial styloconic) with a battery of carbohydrates. These sensilla responded exclusively to sucrose, glucose and inositol. Second, we determined the response properties of the carbohydrate-sensitive taste cells within both sensilla. We found that one class of carbohydrate-sensitive taste cell responded to sucrose, and two other classes each responded to glucose and inositol. Third, we examined the initial biting responses of caterpillars to disks treated with solutions containing single carbohydrates (sucrose, glucose or inositol) or binary mixtures of these carbohydrates. The only solutions that stimulated sustained biting were those that activated all three classes of taste cell (i.e. sucrose+inositol or sucrose+glucose). We propose that the brain of M. sexta monitors input from the different classes of carbohydrate-sensitive taste cell, and generates protracted feeding responses only when all three classes are activated.

“…Taste sensilla from all parts of the flagellum were included in the experiments. The recording glass electrode was connected to a TastePROBE amplifier (10ϫ; Syntech, Hilversum, The Netherlands) (Marion-Poll and Van der Peers, 1996) and the signals filtered (low pass 50·Hz and high pass 3000·Hz) using the CyberAmp 320 from Axon Instruments (Burlingame, CA, USA). The reference electrode was a 1·mm AgCl-coated silver wire placed in the moth abdomen.…”

Section: Experiments 2 Antennal Gustatory Neuron Responses To Quinine mentioning

confidence: 99%

Effects of two bitter substances on olfactory conditioning in the moth Heliothis virescens

Jørgensen

Stranden

Sandoz

et al. 2007

-1 sucrose concentration gave similar acquisition, retention and extinction performances. Experiments involving preexposure or facilitated extinction with an odour paired with quinine, sinigrin or no tastant showed a latent inhibitory effect, as well as an aversive effect of quinine and, to a lesser extent, of sinigrin. The results suggested that the two tastants may act as negative reinforcers in H. virescens.