A pharmacological analysis of an associative learning task: 5-HT(1) to 5-HT(7) receptor subtypes function on a pavlovian/instrumental autoshaped memory

Abstract

Recent studies using both invertebrates and mammals have revealed that endogenous serotonin (5-hydroxytryptamine [5-HT]) modulates plasticity processes, including learning and memory. However, little is currently known about the mechanisms, loci, or time window of the actions of 5-HT. The aim of this review is to discuss some recent results on the effects of systemic administration of selective agonists and antagonists of 5-HT on associative learning in a Pavlovian/instrumental autoshaping (P/I-A) task in rats. The results indicate that pharmacological manipulation of 5-HT1-7 receptors or 5-HT reuptake sites might modulate memory consolidation, which is consistent with the emerging notion that 5-HT plays a key role in memory formation.

Figure 1

Cognitive processes and abilities potentially affected by time of drug administration.

Figure 2

Autoshaping Pavlovian/instrumental. (A) The autoshaping chamber. (B) Rat at the beginning of autoshaping session. (C) Rat showing autoshaped lever-press response. (D) Rat consuming the US-food pellet. (E) Autoshaping Pavlovian/instrumental scheme. (F) Percentage of CRs during an autoshaping session after different pretraining conditions (from left to right): Pavlovian/instrumental, only CS, only US, Pavlovian autoshaping, and operant level. *Values significantly different from those of the P/I-A trained group (P < 0.05 by Dunnett's t test)