Figure 3.

MVP2 Modulates MP1 Oscillations after Paired Training

(A) After paired training, flies were stored either at 33°C for 1 hr to block MVP2 neurons or at 25°C for permissive controls; flies were thus imaged 1.5 hr after training. When MVP2 activity was blocked for 1 hr after paired training (30E11-LexA;R83A12-Gal4 > AOP-GCaMP3;UAS-Shi^ts flies at 33°C), the frequency of MP1 oscillations was significantly higher than in the permissive-temperature condition (paired 25°C, 30E11-LexA;R83A12-Gal4 > AOP-GCaMP3;UAS-Shi^ts flies) and genotype-control condition (paired 33°C, 30E11-LexA;+ > AOP-GCaMP3;UAS-Shi^ts flies) (n = 9), F(3, 32) = 4.83, p < 0.05. Similarly to the oscillations frequency, the quality factor of MP1 calcium oscillation was increased, whereas the amplitude of MP1 calcium oscillations was not significantly affected by paired training or blocking of MVP2 activity (see Figure S3). Control experiments were done immediately after conditioning, using both 30E11-LexA;R83A12-Gal4 > AOP-GCaMP3;UAS-Shi^ts and 30E11-LexA;+ > AOP-GCaMP3;UAS-Shi^ts flies to assess that the association between the odorant and the sugar (paired protocol) induced an increase in both the frequency and the quality factor of MP1 oscillations compared to an unpaired protocol in which the presentation of the sugar is done before odor presentation (see Figure S3). The amplitude of MP1 oscillations was not modified between paired and unpaired protocols (see Figure S3). Illustrative examples of MP1 neuron recordings are displayed for each genotype and condition; controls are indicated in black, and the condition in which MVP2 neuron activity is blocked is indicated in red. Time courses of temperature shifts are displayed above the MP1 recordings. C, conditioning, Im, imaging.

(B and C) In (B), MP1 inhibition immediately after conditioning for 0.75-hr impaired LTM (n = 24), F(2, 71) = 7.24, p < 0.01; whereas in (C), MP1 inhibition from 0.75 hr to 1.25 hr did not affect LTM (n = 12), F(2, 33) = 0.27, p = 0.76.

(D and E) In (D), MP1 activation immediately after conditioning for 0.5 hr did not affect LTM (n = 18), F(2, 51) = 2.01, p = 0.14; whereas in (E), MP1 activation from 0.5 hr to 1 hr after conditioning impaired LTM (n = 16), F(2, 45) = 5.26, p < 0.01. LTM at the permissive temperature was normal (see Figure S3M). Time courses of temperature shifts are displayed above the performance index histograms. (C, conditioning; T, test). Red or green periods in the time courses represent when neurotransmission was blocked (Shi^ts experiments) or activated (TrpA1 experiments), respectively.

Error bars indicate mean ± SEM. Statistical tests were performed using one-way ANOVA. ^∗p < 0.05; ^∗∗p < 0.01, in post hoc comparison; ns, not significant.