Operating procedure to secure a fly to record from its taste sensilla on the proboscis

1 - The starting point

A magnet stub is topped with sticky paste (UHU Yellow Patafix).

2 - A fly is strapped on the Patafix

The fly was numbed with cold ((3-10 min). We use regular transparent tape cut into fine strips. Once the fly is strapped like this, you have time to do the following steps

3 - Fly deprived of its legs

Sometimes, it is helpful to remove the legs which may come over the proboscis

4 - Form a platform for the reference electrode.

Moulding patafix like this will provide a support to a glass electrode, with a fine tip, filled with Ringer.

5 - Insert the reference electrode

The reference electrode is inserted into the abdomen under visual control.

5 - Insert the reference wire

Insert a fine silver wire into the glass electrode and secure it in place with straps of tape and secure it firmly to the rod. This is a cricical step in that it is easy to move inadvertendly the glass electrode and crush your preparation.

7 - Fix the proboscis in place

Using finer strips of tape, place them over the shaft of the proboscis. Usually, placing the stripes crossing over the proboscis will do the job. This is to prevent the proboscis from moving, to have it expanded and to orient the area you want to record from so that it will be accessible to a stimulation electrode

8 - Recording setup

This is the full recording setup we use to do tip-recording.

9 - Stimulation elements

To stimulate your fly with different solutions, you will need to prepare them in advance, as well as glass capillary electrodes of the right size.

10 - Connecting your fly to the ground

The fly sticked on the magnetic stub is placed over a moveable arm and oriented in the proper position under the microscope. The silver wire is connected to the ground with an alligator clip.

11 - Overview of the proboscis in place

The proboscis is fully extended. The fly is oriented so that the hairs to investigate are oriented parallel to the x-axis of the micromanipulator supporting your stimulating electrode. The quality of your recordings depends very much on this orientation because it will minimize contact artifacts.

12 - Power up the amplifier

Once the fly is in place, you should then power up your equipment. As an amplifier, we use a 2 channels CyberAmp, which is driven by a computer.

13 - Power up the TasteProbe

For tip-recording, we use a TasteProbe which is designed to minimize the initial contact voltage artefact. This amplifier waits until a contact is made, once the contact is made, the incoming signal is stored into a capacitor during 1-5 ms and then, substracted from this value.

14 - Start your recording program

As for recording the waves, we use a custom program, dbWave, that interfaces to a Data Translation 16bits USB A/D card and to the CyberAmp.

15 - Prepare your recording bout

Once you are ready to stimulate, describe your recording parameters that will be stored along with the electrophysiological data and also into a database.

16 - Place your stimulating electrode

A glass capillary with the proper tip opening and containing the stimulus (salt, sugar, alcaloid) together with a conducing salt solution (KCl 10-3 M), is placed over a silver wire connected to the input of a x1 or x10 preamplifier (connected to the tasteProbe).

17 - Approach micromanipulator

Once the capillary is placed over the probe, approach the micromanipulator from the preparation.

18 - Ready to stimulate

Once the micromanipulator is close to the prep, you can look at the electrode under the microscope and cap the tip of one taste hair

19 - Preparation under the microscope

20 - Approaching the stimulus electrode

The stimulus electrode is approached from the proboscis and will cover the chosen hair (with the help of a map, you can actually stimulate the same hair from fly to fly).

21 - TasteProbe in waiting mode

TasteProbe is convenient because it will "wait" until you contact the hair. Once a contact is detected, it will send a TTL signal to the computer to start the data acquisition, compensate the incoming signal for its DC offset and then substract this value from the signal during the time of the recording (usually, we use 2 s recordings).

22 - Stimulation

Final approach: you cap a hair et voilà!