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Gimpl MP, Gormezano I, Harvey JA. 
“Effects on Learning as Measured by Classical Conditioning of the Rabbit Nictitating Membrane Response”. 
J.Pharmacol.Exp.Ther.. 1979;208(2):330-34.
The effects of LSD on learning as measured by conditioning of the rabbit nictitating membrane response were studied. Tone and light conditioned stimuli (CS) were presented 800 msec before delivery of the unconditioned stimulus ta 100 maec electric shock to the skin over the paraorbital area of the head) to New Zealand White rabbits (1.9-2.4 kg). Extension of the membrane to the CSs in 800 msec prior to shock was a conditioned esponse (CR), while extension to shock onset was an unconditioned response (UCR). LSD (Sandoz) (1-300 nmol/kg) was injected i.v. 30 min before each daily session. In paired CS -UCS procedure, LSD (1-100 nmol/kg) produced a dose-dependent rise in % CRs with maximum effect at 30-100 nmol/kg produced non-significant effects. The frequency of responding under unpaired CS, UCS procedure was low and was unaffected by LSD. Under paired CS -UCS, animals at each LSD dose showed significant acquisition of conditioned response and reached asymptotic levels (86-98%) by day 10. 1-100 nmol/kg LSD enhanced acquisition, while 300 nmol/kg retarded it. LSD similarly improved acquired CRs in daily sessions as well as over 10 days. Under unpaired CS, UCS there were no consistent changes within days or over 10 days. LSD peak enhancement of acquisition occurred at 30 nmol/kg, where animals required fewer trials than controls. The frequency of baseline responding during adaptation was 1.7%, and the frequency of baseline responding during the 800 msec during unpaired CS, USC was low and unaffected by LSD. Frequency of baseline responding fell across days, and LSD had no effect on this decline. LSD had no effect on UCR in unpaired CS, UCS, but mean UCR amplitude fell over trials and across days, and LSD had no effect on these falls. 300 nmol/kg LSD retarded CR acquisition across 12 days of conditioning. Reversal of drug conditions on day 13, caused a fall in acquired CR responding. The fall in responding not significantly different between animals shifted from vehicle to LSD and those from LSD to vehicle.
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