Behavioral Characterization of GCLM-Knockout Mice, a Model for Enhanced Susceptibility to Oxidative Stress

Abstract

Glutathione (GSH) is a major player in cellular defense against oxidative stress. Deletion of the modifier subunit of glutamate cysteine ligase (GCLM), the first and the rate-limiting enzyme in the synthesis of GSH, leads to significantly lower GSH levels in all tissues including the brain. GCLM-knockout (Gclm(-/-)) mice may thus represent a model for compromised response to oxidative stress amenable to in vitro and in vivo investigations. In order to determine whether the diminished GSH content would by itself cause behavioral alterations, a series of behavioral tests were carried out comparing young adult Gclm(-/-) with wild-type mice. Tests included the rotarod, acoustic startle reflex and prepulse inhibition of the startle reflex, open field behavior, and the platform reversal variant of the Morris Water Maze. Results showed no differences between Gclm(-/-) and wild-type mice in any of the neurobehavioral tests. However, more subtle alterations, or changes which may appear as animals age, cannot be excluded.

Figure 1

Rotarod. Mice were placed on a rotarod, and latency to fall from the rotarod was recorded for each of 4 successive trials. Trials were separated by a 1 min interval. Results are shown as mean ± SE (n = 12-13). WT: wild-type mice; GCLM-KO: Gclm^−/− mice.

Figure 2

Prepulse inhibition/startle. Auditory startle response was measured using a startle chamber. Startle amplitude was similar in wild-type and Gclm^−/− mice, and a 70 dB prepulse inhibited the subsequent startle response to a similar extent in wild-type and Gclm^−/− mice. Results are shown as mean ± SE (n = 12-13). WT: wild-type mice; GCLM-KO: Gclm^−/− mice.

Figure 3

Open-field behavior. Mice were placed in an open-field chamber, and movements and behaviors were recorded for 15 min using infrared beam breaks in the horizontal or vertical plane. There were no differences between Gclm^−/− and wild-type mice in ambulatory activity, time spent in different parts of the chamber, stereotypic movements, or vertical movements. Results are shown as mean ± SE (n = 12-13). WT: wild-type mice; GCLM-KO: Gclm^−/− mice.

Figure 4

Morris water maze. Mice were tested in the Morris water maze for 14 days, 3 trials per day. During the acquisition phase (days 1–7), mice learned to find a submerged platform using spatial cues. On the 8th day, the platform was moved to the opposite quadrant and mice were tested for their ability to find the new platform location. There were no significant differences in acquisition or reversal between Gclm^−/− and wild-type mice. Results are shown as mean ± SE (n = 12-13). WT: wild-type mice; GCLM-KO: Gclm^−/− mice.