Perinatal hypothyroidism effects on step-through passive avoidance task in rats.

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.