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Brown K, Cooper SJ.
“Effects of lysergic acid diethylamide on auditory and visual discrimination in the rat.”.
Brit J Pharmacol. 1975;54:234P.
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Abstract
The effect of LSD on either visual or auditory discrimination was studied in rats matched for discrimination performance. A drug may affect discrimination either by changing stimulus sensitivity or by shifting the criterion for responding. A method of analysis, derived from signal detection theory (SD'), was used to assess independent effects on these two factors. Twelve adult, male, hooded rats (300 g) were used. Each animal was first trained on a DRL (differential reinforcement of low rate) schedule. A signal indicated the availability of reinforcement. After each reinforced response, the interval to the next signal was varied unpredictably between 9 and 27 s (mean delay 18 s). A response, 9 s or less before the signal, postponed The study demonstrated a reduction in the reinforcement for a further 9 s. The schedule yielded a low but constant response-rate. One group of rats (n=6) was trained with a light signal, the second group (n = 6) with a tone, and the two groups were matched for discrimination performance. Each rat was trained 45 min per day for 44 days before the experiments, to produce consistent baseline responding. A SDT analysis was used to determine two parameters, Ač a measure of stimulus sensitivity, and BČ. a measure of response bias. The drugs were lysergic acid diethylamide tartrate (Sandoz) and methy - sergide bimaleate (Sandoz) (a control for rat peripheral effects). The injection conditions were 0.005, 0.01, 0.05, 0.25 mg/kg LSD, 0.50, 1.00 mg/kg methysergide, and distilled water. The . n, A Rays solutions were made up in distilled water and v injected i.p. in the volume 1.0 ml/kg. Each rat was tested under each injection condition, with order of injection counterbalanced within each group. Injections were given at 48 h intervals. Forstatistical analysis results on an injection day were compared with the preceding day's baseline performance. LSD effects were found to be comparable for the two groups. Total responses were reduced by on average 62.7% (P< 0.001) at the highest dose of LSD (0.25 mg/kg). There were no other significant drug effects on response rate. There was a reduction in A' (i.e. a decrease in stimulus sensitivity) at 0.25 (P< 0.005) and at 0.05 mg/kg LSD (P< 0.005). No other changes in A' under - any other injection conditions occurred. The sensitivity changes were not due to changes in response bias (B ), since there were no consistent number of responses at the highest dose of LSD and independently of this,a decreasein sensitivity and independently of this,a decreasein sensitivity 0.25 mg/kg LSD. There were no drug effects upon response bias.
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