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Effects of Juvenile Methylphenidate on Long‐Term Retention in Adulthood
Author(s) -
McWaters Mercedes,
Anderson Eden,
Matuszewich Leslie
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.662.6
Subject(s) - methylphenidate , juvenile , water maze , psychology , medicine , audiology , physiology , attention deficit hyperactivity disorder , developmental psychology , psychiatry , hippocampus , biology , genetics
Methylphenidate (MPH), or Ritalin, is a commonly prescribed psychostimulant for the alleviation of symptoms in children diagnosed with Attention Deficit Hyperactivity Disorder (ADHD; Centers for Disease Control and Prevention, 2011). Previous research has demonstrated the therapeutic benefits of MPH in the short‐term, but research on the long‐term effects after chronic juvenile exposure is limited. One potential long‐term effect is the alteration of performance on learning and memory tasks, such as the Morris water maze. Prior research in our lab has shown that chronic juvenile MPH treatment enhances the retention of the hidden platform location in the water maze on the first trial of acquisition across training days and MPH‐treated female rats have the greatest improvement across trials within the first day of training. Based on these findings, we hypothesized that MPH may be affecting males' and females' learning and memory differently following juvenile exposure to MPH. Therefore, the purpose of this study was to further investigate the effects of chronic juvenile MPH on long‐term retention in a modified water maze task in male and female rats. This modified task allowed us to explore the potential juvenile treatment and sex differences on short‐term and long‐term memory consolidation. Juvenile rats received an oral dose of 2.0 mg/kg MPH or vehicle on a vanilla wafer from postnatal day 20–34. In adulthood, rats received three sequential training trials to locate a hidden platform in the water maze and then received an acute oral 2.0 mg/kg MPH dose. Short‐term memory was assessed two hours after an acute MPH dose and long‐term memory was assessed 24 hours after acute MPH. Overall, rats showed decreased latencies and distances to find the hidden platform across training, short‐term, and long‐term memory trials, suggesting that all rats learned the task regardless of juvenile treatment. There was a sex by juvenile treatment interaction for latency and distance to find the platform on the long‐term memory trial, suggesting that previous MPH treatment enhanced performance in female rats, but not male rats. To assess retention of the memory of the hidden platform location, rats received a single retention trial once a week for five weeks. All rats continued to learn/reconsolidate the memory of the hidden platform across weeks, irrespective of sex or juvenile treatment. Overall, these results suggest that juvenile MPH may be facilitating females' memory consolidation, as assessed by the long‐term memory trial. These data support our previous findings that female rats may be more sensitive to the long‐term effects of juvenile MPH treatment than male rats.