1. The use of angiotensin-converting enzyme (ACE) inhibitors during pregnancy is contraindicated because of their association with increased risks of fetopathy, including central nervous systems malformations. In addition, some reports have shown that renin-angiotensin system components are expressed differently during embryonic development and adulthood in the rat. 2. Because angiotensin II and its derivative peptides have been implicated in anxiety and modulation of nociception, the aim of the present study was to investigate whether inhibiting ACE during prenatal and neonatal periods would alter behavioural plasticity in adult male offspring rats. 3. Female Wistar rats were treated with captopril (2 mg/mL water; approximately 200 mg/kg per day) during pregnancy and lactation. At adulthood, the offspring were subjected to the open field, elevated plus maze, social interaction, forced swimming and tail flick tests. 4. Perinatal captopril treatment significantly increased ambulation (33%; P < 0.05) and decreased resting time (37.5%; P < 0.05) in the open field test. Perinatal captopril treatment did not alter any of the behavioural parameters of the elevated plus maze; however, captopril treatment did cause a significant increase in social interaction (75.3%; P < 0.05). In the forced swimming test, there was an increased latency period (102.9%; P < 0.001) and a decreased immobility period (38.7, P < 0.05) in rats treated with perinatal captopril. In the tail flick test, perinatal captopril treatment significantly reduced the latency time (26.3%; P < 0.01). 5. The data show that ACE inhibition during prenatal and neonatal periods affects behavioural responses in adult offspring rats, suggesting that ACE is required for the development of neural systems that are associated with adult anxiety and nociceptive behavioural responses.

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