This page is meant to document the results from a series of experiments under different saline conditions, as performed by Matt Collie in the spring of 2022. Behavior was assessed based on 1) the fly’s directional velocity distribution and 2) the fly’s engagement with the stimulus (in this case, chasing an oscillating dark bar).

Quick disclaimer - many of these experiment conditions have a sample size of 1 or 2, so please take findings with a grain of salt.

Standard Example:

Sugar#

Glucose - increasing the concentration of glucose from 10mM to 50-75mM dramatically increases the fly’s walking speed (peak ~10-12mm/s) and elicited robust and sustained chase behavior.

  • However, this effect was only observed when the brain was sheathed. De-sheathing results in no walking at all.

  • Effects of removing the following:
    • NaCl (70mM) - turning behavior, but without sustained forward walking
    • NaCl (85mM) and NaHC03 (15mM) - turning behavior, but without sustained forward walking
    • NaHCO3 (4mM) - poor behavior

Sucrose - conversely, adding 50-75mM sucrose only slightly increases the fly’s walking speed (peak ~4-6mm/s) and did not elicit sustained chase behavior.

Trehalose - add

Basic Ions#

Sodium - increasing the concentration of sodium from 103mM to 135mM caused no noticeable difference in walking behavior

  • When de-sheathed - turning behavior, but without sustained forward walking

Potassium - increasing the concentration of potassium from 3mM to 35mM does not immediately effect behavior, but tends to result in no walking after 15min of walking

Buffer#

Sodium Bicarbonate - increasing the concentration of sodium bicarbonate from 26mM to 50mM increases the fly’s walking speed (peak ~4-5mm/s) and elicited sustained chase behavior.

  • However, this effect was only observed once the brain was de-sheathing. Sheathed flies showed no noticeable change in walking behavior as compared to standard saline.
  • Decreasing the concentration of sodium bicarbonate from 26mM to 4mM does not immediately effect behavior, but tends to result in poor behavior after 30-45min of walking.

TES/HEPES - no noticeable difference in walking behavior when switching between the two as compared to standard saline.

Other Recipes#

CSHL Saline - No noticeable difference in walking behavior when using the CSHL saline recipe (e.g., used by Ruta Lab) as compared to standard saline.

Hemolymph-like Saline - No walking at all when using the HL modified saline used at the drosophila larva NMJ as described by Stewart/Wu 1995

Backward Labeling with neurobiotin and biocytin Applying Dispase Forward