A threshold for the protective effect of over-reinforced passive avoidance against scopolamine-induced amnesia.

Abstract

Acetylcholine-receptor blockers produce amnesia of aversively motivated behaviors. However, when animals are submitted to relatively high intensities of footshock (over-reinforcement), anticholinergic treatment does not induce memory impairments. The aim of this work was to determine whether the antiamnesic effect produced by increasing the magnitude of the negative reinforcer is gradually established or if a threshold should be reached to obtain such an effect. Wistar rats were trained in passive avoidance using 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0 mA; 5 min after training they were given one systemic injection of scopolamine (8 mg/kg). An amnesic state was produced in the groups that were trained with the lower intensities (2.5-2.7 mA); with the three higher intensities near-perfect retention was evident. These results suggest that acetylcholine is critically involved in memory consolidation, and that by increasing the magnitude of the negative reinforcer, a threshold is reached where cholinergic activity of the nervous system is not necessary for the development of the consolidation process.

• Authors: S E Cruz-Morales, M Duran-Arevalo, M A Diaz Del Guante, G Quirarte, R A Prado-Alcala
• Journal: Behavioral and neural biology (Behav Neural Biol) Vol. 57 Issue 3 Pg. 256-9 (May 1992) ISSN: 0163-1047 [Print] United States
• PMID: 1616458 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Scopolamine

Topics

• Animals
• Avoidance Learning (drug effects)
• Brain (drug effects)
• Cholinergic Fibers (drug effects)
• Male
• Mental Recall (drug effects)
• Overlearning (drug effects)
• Rats
• Rats, Inbred Strains
• Reinforcement Schedule
• Retention, Psychology (drug effects)
• Scopolamine (pharmacology)