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Perinatal hypothyroidism effects on step-through passive avoidance task in rats
Sònia Darbra1, Ferran Balada, Maria Assumpció Martí-Carbonell
1Departament de Psicobiologia i Metodologia en Ciències de la Salut, Unitat de Psicobiologia, Institut de Neurociències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.
Insights
Perinatal hypothyroidism in rats impairs long-term memory retention in a passive avoidance task. This condition, induced by methimazole exposure, affects cognitive function, particularly recall after 24 hours and 7 days.
Area of Science:
- Neuroscience
- Endocrinology
- Developmental Biology
Background:
- Neonatal hypothyroidism is linked to learning deficits and increased activity.
- Limited data exists on the behavioral impact of perinatal hypothyroidism (prenatal and postnatal).
Purpose of the Study:
- To investigate the effects of perinatal hypothyroidism on the acquisition and retention of learned responses in male Wistar rats.
- To assess short-term (1 hour) and long-term (24 hours, 7 days) memory retention following perinatal hypothyroidism.
Main Methods:
- Perinatal hypothyroidism induced in pregnant and lactating rats using methimazole (0.2 mg/ml in drinking water) from embryonic day 9 to postnatal day 21.
- Cognitive function assessed at 50 days using a step-through passive avoidance task.
- Behavioral analysis focused on acquisition and retention intervals of 1 hour, 24 hours, and 7 days.
Main Results:
- Rats exposed to perinatal hypothyroidism exhibited poorer performance in long-term retention tests (24 hours and 7 days).
- Methimazole-treated rats demonstrated longer retrieval latencies in short-term retention tests (1 hour) compared to controls.
- The long-lasting effects of perinatal hypothyroidism on passive avoidance response retention are dependent on initial training retention.
Conclusions:
- Perinatal hypothyroidism significantly impacts long-term memory retention in a passive avoidance task.
- The observed cognitive deficits are persistent and influenced by the initial learning consolidation.
- These findings highlight the critical role of thyroid hormones during prenatal and postnatal development for cognitive function.
Abstract:
Previous studies have documented a decrease in the ability of neonatal hypothyroid animals to learn and habituate to maze tests, and an increase in spontaneous activity. However, there is little information about the effects of perinatal (i.e., prenatal and postnatal) hypothyroidism on behaviour. The present study was designed to assess whether perinatal hypothyroidism in rats induces alteration on acquisition and/or short- and long-term retention of a learned response in male Wistar rats. Perinatal hypothyroidism was induced by prolonged (E9-P21) exposure of pregnant and lactating dams to methimazole (administered orally in drinking water, 0.2 mg/ml). Cognitive function was tested at 50 days by means of a step-through passive avoidance task. The effects of perinatal hypothyroidism on the retention of the passive avoidance response are long lasting being, however, highly dependent on the retention after the original training. Our results showed that methimazole-treated rats performed more poorly when retention was tested at long-term (24 h and 7 days) retention interval. Instead, methimazole-treated rats showed longer retrieval latencies than the control ones did when retention was tested at short term (1 h).
