Ketamine blocks a conditioned taste aversion (CTA) in neonatal rats

Area of Science:

• Neuroscience
• Developmental Psychology
• Pharmacology

Background:

• Previous research indicated ketamine potentiates conditioned taste aversion (CTA) in E18 rat fetuses.
• The current study investigates ketamine's effects on CTA in neonatal rats, contrasting with fetal findings.
• Understanding NMDA receptor blockade's impact on memory formation across developmental stages is crucial.

Purpose of the Study:

• To explore ketamine's effects on the formation, retention, and expression of CTA in neonatal rats.
• To determine if ketamine administration on the day of birth blocks CTA acquisition.
• To investigate the role of N-methyl-D-aspartate (NMDA) receptor blockade in neonatal memory development.

Main Methods:

• Neonatal Sprague-Dawley rats received intraperitoneal injections of ketamine (0.1, 10, or 70 mg/kg) or saline on their birth day.
• Conditioned taste aversion was induced using saccharin (Sac) and lithium chloride (LiCl) or saline.
• CTA was evaluated using nipple taste tests (NTT) and two-bottle consumption tests post-weaning.

Main Results:

• Neonates receiving saline controls acquired CTA, avoiding saccharin-associated nipples.
• Ketamine administration on the day of birth (P0) blocked CTA acquisition and expression in NTT.
• High-dose ketamine did not impair taste perception but prevented neophobia towards saccharin.

Conclusions:

• Ketamine administration blocks the formation of conditioned taste aversion in neonatal rats.
• These findings contrast with ketamine's potentiating effect on CTA in fetal rats.
• NMDA receptor blockade's influence on memory formation is dependent on the brain's developmental stage.