Changes

Selection, construction and programming of the apparatus hardware was modified from open-source syringe pump manuscripts by Longley et al (2017) and Wijen et al (2014). A capacitive touch sensor (Adafruit MPR121) is connected to the rats’ sipper tubes and programmed to detect each lick from the spout with millisecond accuracy. The capacitive touch sensor relays its information to an Arduino- compatible microcontroller (Teensy-LC) which subsequently signals a stepper motor driver (Pololu DRV8825) to turn a stepper motor (NEMA-17, 200 steps/rev, 12V, 350mA, resulting in the release of 4–8 μl liquid per lick from a 20 ml syringe connected to the stepper motor (Figure 4). The syringe pumps liquid into the rat’s chronic gastric catheter at a rate of 1 ml/min over 10 min. This infusion rate is slow enough that the stomach easily accommodates the fill and allows for gastric emptying into the intestine at a normal rate.

Selection, construction and programming of the apparatus hardware was modified from open-source syringe pump manuscripts by Longley et al (2017) and Wijen et al (2014). A capacitive touch sensor (Adafruit MPR121) is connected to the rats’ sipper tubes and programmed to detect each lick from the spout with millisecond accuracy. The capacitive touch sensor relays its information to an Arduino- compatible microcontroller (Teensy-LC) which subsequently signals a stepper motor driver (Pololu DRV8825) to turn a stepper motor (NEMA-17, 200 steps/rev, 12V, 350mA), resulting in the release of 4–8 μl liquid per lick from a 20 ml syringe connected to the stepper motor (Figure 4). The syringe pumps liquid into the rat’s chronic gastric catheter at a rate of 1 ml/min over 10 min. This infusion rate is slow enough that the stomach easily accommodates the fill and allows for gastric emptying into the intestine at a normal rate.

Using a protocol adapted from Elizalde & Sclafani (1990), unconditioned stimuli (glucose or saline) will be infused intragastrically as the animals orally sample distinct flavored solutions. With this "Electronic Esophagus" preparation utilized by Sclafani and others, animals form robust and persistent preferences for the flavored solution that is paired with glucose infusions.

Using a protocol adapted from Elizalde & Sclafani (1990), unconditioned stimuli (glucose or saline) will be infused intragastrically as the animals orally sample distinct flavored solutions. With this "Electronic Esophagus" preparation utilized by Sclafani and others, animals form robust and persistent preferences for the flavored solution that is paired with glucose infusions.