A spoonful of sugar helps the medicine go down: a novel technique to improve oral gavage in mice

Abstract

Oral gavage is a common route of precise oral dosing for studies in rodents. Complications including tracheal administration, esophageal trauma, and aspiration are common and usually related to animal resistance to the procedure, and the stress induced by oral gavage can be a confounding variable in many studies. The taste of sucrose conveys a pacifying and analgesic effect in newborns, whereas sour solutions can induce the swallow reflex in humans that are dysphagic. We hypothesized that precoating a gavage needle with sucrose or citrate (or both) would pacify mice and induce them to swallow, reducing the stress and complications associated with the technique. To validate this hypothesis, we quantitated time to passage, stress-related behavioral reactions to the procedure, and plasma corticosterone levels in mice after precoating gavage needles with water, sucrose, citrate, sucrose and citrate, or sodium chloride prior to oral gavage. Precoating needles with sucrose reduced the time to passage, decreased observable stress-related reactions to the procedure, and maintained plasma corticosterone levels similar to those in ungavaged control mice. Coating needles with water, sucrose and citrate, or citrate had no beneficial effects on these parameters. Our findings describe a novel, validated technique that measurably decreases signs of stress and thereby improves animal welfare during oral gavage. Furthermore, the use of sucrose may be a valuable tool to refine other minor or nonsurgical procedures in the field of laboratory animal research.

Figure 1.

Example of mouse restraint and oral gavage technique. Left, Demonstration of handling technique to immobilize subject for oral gavage by tightly scruffing with nongavage hand. Center, Introduction of the gavage needle into oral cavity and start of the time to passage measurement. Right, Passage of the gavage needle to stopping point in the esophagus and stop of the time to passage measurement.

Figure 2.

Time to needle passage during oral gavage. The time to passage from the introduction of the gavage needle to needle stopping point was recorded for 36 mice gavaged with water- or sucrose-coated needles for each gavage trial (n = 16 to 20 per group). Mice were assigned randomly to treatment groups before each trial. Values are expressed as mean ± SEM. *, P < 0.001 by ANCOVA with Bonferroni post hoc analysis.

Figure 3.

Average time to passage for repeated treatments by using gavage needles coated with various tastants. Average time to passage for each group of mice gavaged with needles coated with water, sucrose, citrate, sucrose plus citrate, or NaCl (n = 8 per group) is shown. Mice were gavaged with the same treatment throughout all trials.

Figure 4.

Plasma corticosterone levels after oral gavage by using gavage needles coated with various tastants. Naïve mice were gavaged with needles coated with water, sucrose, citrate, sucrose plus citrate, or NaCl solutions, and blood was collected 1 h after dosing by cardiocentesis. (A) Plasma corticosterone levels of tastant treatment groups were compared with those of control mice that did not undergo oral gavage procedure and of mice gavaged with water-coated needles. Values are expressed as mean ± SEM (n = 5 per group; *, P < 0.001 (ANOVA with Tukey post hoc analysis) compared with nongavaged controls; #, P < 0.001 (ANOVA with Tukey post hoc analysis) compared with group that received water-coated gavage needles. (B) Plasma corticosterone levels after oral gavage procedure in groups of mice by using water- or sucrose-coated needles with a total procedure time of 10 s. Values are expressed as mean ± SEM (n = 8 per group). +, P < 0.05 (2-tailed Student t test).