Location

Jereld R. Nicholson Library

Subject Area

Psychology

Description

Alcohol’s (A) capacity to impair learning and memory has been well documented in the Morris Water Maze (MWM) but few studies have examined methylphenidate’s (MPH) impact on MWM performance (Haidun et al., 2010; Zeise et al., 2007). Even fewer studies have evaluated concurrent administration of these two drugs in adolescent rats (see Markwiese, et al., 1998). This project used a rat model of adolescent drug use to examine individual effects of MPH and A, as well as polypharmacy interactions between MPH and A, on MWM spatial acquisition and retention.

Thirty-two adolescent (P30) male Long-Evans hooded rats were used. Subjects were assigned to one of 4 conditions based on drug administered prior to 6 consecutive acquisition sessions. Animals received 2 i.p. injections prior to each session. The methylphenidate group (MPH+S) received 2 mg/kg MPH and 1 ml/kg saline solution (S), the alcohol group (A+S) received 2 g/kg ethanol and S, the methylphenidate and alcohol group (MPH+A) received both MPH and A, and the saline control group (S+S) received S injections. MPH was administered 50 mins prior to each session and A administered 20 mins prior to each session. Each session consisted of 4 trials and rats swam from one of four start locations (N,E,S,W) to a submerged platform in the NE quadrant. Trial duration was 60 seconds and rats remained on the platform for 10 secs. Performances were video recorded, and latency and swim accuracy scored. Whishaw Corridors established a direct swim path from start location to platform and an error was recorded when swim paths exited the corridor. On day 7, the submerged platform was removed and a single, 60 sec retention test was conducted with no drug administered prior to test. Amount of time spent swimming in the NE quadrant was analyzed to assess retention.

Acquisition: Both dependent measures, latency and swim accuracy, yielded similar outcomes. Factorial ANOVAs and post hoc tests showed improvement across training sessions for all groups. Importantly, the MPH+A group was impaired relative to all other conditions, and the S+S group performed better than the A group. No significant differences were observed between S+S and MPH+S groups.

Retention: A one-way ANOVA of swim time in the NE quadrant revealed longer swim times for the S+S group compared to the A+S group, and longer swim times for the MPH+S group compared to the A+S group. No other significant differences were observed.

While all groups improved performance during acquisition, methylphenidate + alcohol compromised spatial learning, and alcohol alone impaired learning relative to controls. Interestingly, measures of retention indicated only alcohol diminished spatial memory in adolescent rats.

Comments

2nd place award

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May 16th, 4:30 PM May 16th, 6:00 PM

The Separate or Concurrent Effects of Methylphenidate and Alcohol on Acquisition and Retention of the Morris Water Maze in Adolescent Rats

Jereld R. Nicholson Library

Alcohol’s (A) capacity to impair learning and memory has been well documented in the Morris Water Maze (MWM) but few studies have examined methylphenidate’s (MPH) impact on MWM performance (Haidun et al., 2010; Zeise et al., 2007). Even fewer studies have evaluated concurrent administration of these two drugs in adolescent rats (see Markwiese, et al., 1998). This project used a rat model of adolescent drug use to examine individual effects of MPH and A, as well as polypharmacy interactions between MPH and A, on MWM spatial acquisition and retention.

Thirty-two adolescent (P30) male Long-Evans hooded rats were used. Subjects were assigned to one of 4 conditions based on drug administered prior to 6 consecutive acquisition sessions. Animals received 2 i.p. injections prior to each session. The methylphenidate group (MPH+S) received 2 mg/kg MPH and 1 ml/kg saline solution (S), the alcohol group (A+S) received 2 g/kg ethanol and S, the methylphenidate and alcohol group (MPH+A) received both MPH and A, and the saline control group (S+S) received S injections. MPH was administered 50 mins prior to each session and A administered 20 mins prior to each session. Each session consisted of 4 trials and rats swam from one of four start locations (N,E,S,W) to a submerged platform in the NE quadrant. Trial duration was 60 seconds and rats remained on the platform for 10 secs. Performances were video recorded, and latency and swim accuracy scored. Whishaw Corridors established a direct swim path from start location to platform and an error was recorded when swim paths exited the corridor. On day 7, the submerged platform was removed and a single, 60 sec retention test was conducted with no drug administered prior to test. Amount of time spent swimming in the NE quadrant was analyzed to assess retention.

Acquisition: Both dependent measures, latency and swim accuracy, yielded similar outcomes. Factorial ANOVAs and post hoc tests showed improvement across training sessions for all groups. Importantly, the MPH+A group was impaired relative to all other conditions, and the S+S group performed better than the A group. No significant differences were observed between S+S and MPH+S groups.

Retention: A one-way ANOVA of swim time in the NE quadrant revealed longer swim times for the S+S group compared to the A+S group, and longer swim times for the MPH+S group compared to the A+S group. No other significant differences were observed.

While all groups improved performance during acquisition, methylphenidate + alcohol compromised spatial learning, and alcohol alone impaired learning relative to controls. Interestingly, measures of retention indicated only alcohol diminished spatial memory in adolescent rats.

 

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