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Classical conditioning in the fetal rat: reinforcing properties of dynorphin A (1-13)
E I Varlinskaya1, E S Petrov, W P Smotherman
1Pavlovian Physiological Department, Institute for Experimental Medicine, Russian Academy of Medical Sciences, St. Petersburg, Russia.
This study examined the reinforcing properties of dynorphin A (1-13) in a single-trial classical conditioning paradigm in the E20 rat fetus. Injection of dynorphin into the cisterna magna increased fetal motor activity and reduced facial wiping in a test of perioral cutaneous responsiveness. Dynorphin was effective as an unconditioned stimulus (US) in a classical conditioning paradigm using an artificial nipple conditioned stimulus (CS) and dynorphin A (1-13) US. The association between CS and US was dependent on activity in the kappa opioid system. Re-exposure to the artificial nipple CS after a single pairing of the nipple with dynorphin resulted in conditioned activation of the kappa opioid system. Dynorphin A (1-13) functions as a reinforcer for classical conditioning in the rat fetus after intracisternal or intrahemispheric injection, with the conditioned response depending on route of administration and site of injection.
This study examined the reinforcing properties of dynorphin A (1-13) in a single-trial classical conditioning paradigm in the E20 rat fetus. Injection of dynorphin into the cisterna magna increased fetal motor activity and reduced facial wiping in a test of perioral cutaneous responsiveness. Dynorphin was effective as an unconditioned stimulus (US) in a classical conditioning paradigm using an artificial nipple conditioned stimulus (CS) and dynorphin A (1-13) US. The association between CS and US was dependent on activity in the kappa opioid system. Re-exposure to the artificial nipple CS after a single pairing of the nipple with dynorphin resulted in conditioned activation of the kappa opioid system. Dynorphin A (1-13) functions as a reinforcer for classical conditioning in the rat fetus after intracisternal or intrahemispheric injection, with the conditioned response depending on route of administration and site of injection.