Abstract
Four rats were first trained to make a light-dark discrimination by making electrical stimulation of the brain (ESB) available to them for responses made in the presence of one stimulus (S D), but not in the presence of another stimulus (S Δ). Subjects were then tested following treatment with pilocarpine, scopolamine, and combinations of the two. Pilocarpine (2.5 and 5.0 mg/kg) significantly reduced the rate of reinforced responding, in the presence of S D, but did not affect the rate of unreinforced responding, in the presence of S D. On the other hand, scopolamine (2.5 mg/kg) did not affect response rates during S D, but did significantly enhance responding during S D. Furthermore, when given in combination, the two drugs failed to antagonize eath other's actions. Instead, the outcome was equivalent to the sum of the two separate effects: i.e., decreased responding during S D and increased responding during S Δ.
These results support the conclusions that 1. a pilocarpine-sensitive, inhibitory neural subsystem opposes response activation produced by ESB, in the presence of a discriminative stimulus (S D), and 2. a separate muscarinic inhibitory system which is not sensitive to pilocarpine opposes the activation of non-reinforced responses, i.e., in the presence of S Δ.
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This work was supported in part Grant No. 11015 from the Psychopharmacology Division, American Psychological Association.
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Meliska, C.J., Sawicky, T.E. Differential effects of pilocarpine and scopolamine on the performance of a light-dark discrimination maintained by electrical stimulation of the brain. Psychopharmacologia 36, 29–39 (1974). https://doi.org/10.1007/BF00441379
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DOI: https://doi.org/10.1007/BF00441379