Differential effects of muscarinic receptor blockade in prelimbic cortex on acquisition and memory formation of an odor-reward task

Abstract

The present experiments determined the consequences of blocking muscarinic cholinergic receptors of the prelimbic (PL) cortex in the acquisition and retention of an odor-reward associative task. Rats underwent a training test (five trials) and a 24-h retention test (two retention trials and two relearning trials). In the first experiment, rats were bilaterally infused with scopolamine (20 or 5 µg/site) prior to training. Although scopolamine rats showed acquisition equivalent to PBS-injected controls, they exhibited weakened performance in the 24-h retention test measured by number of errors. In the second experiment, rats were injected with scopolamine (20 µg/site) immediately or 1 h after training and tested 24 h later. Scopolamine rats injected immediately showed severe amnesia detected in two performance measures (errors and latencies), demonstrating deficits in retention and relearning, whereas those injected 1 h later showed good 24-h test performance, similar to controls. These results suggest that muscarinic transmission in the PL cortex is essential for early memory formation, but not for acquisition, of a rapidly learned odor discrimination task. Findings corroborate the role of acetylcholine in consolidation processes and the participation of muscarinic receptors in olfactory associative tasks.

Social memories in rodents: Methods, mechanisms and modulation by stress

“…In contrast, STFP performance was not affected when scopolamine was administered 1 h after training, suggesting that the cholinergic system in the prelimbic cortex is likely important for the acquisition and early consolidation of the task (Carballo-Márquez et al, 2007). Although it was reported that the quality of social interaction between the 'observer' and the 'demonstrator' was not different between sham-and scopolamine-treated animals and that olfaction was intact, other non-specific effects of scopolamine on learning and/or attention cannot be excluded (for further reading, see Klinkenberg and Blokland, 2010).…”

“…Infusion of the muscarinic cholinergic antagonist scopolamine into the prelimbic cortex of rats before or during training impaired STFP performance 24 h after the last training session Carballo-Márquez et al, 2007). In contrast, STFP performance was not affected when scopolamine was administered 1 h after training, suggesting that the cholinergic system in the prelimbic cortex is likely important for the acquisition and early consolidation of the task (Carballo-Márquez et al, 2007).…”

d-cycloserine in the basolateral amygdala prevents extinction and enhances reconsolidation of odor-reward associative learning in rats

“…2A), in accordance with previously described procedures (Quiroz-Padilla, GuillazoBlanch, Vale-Martinez, Torras-Garcia & Marti-Nicolovius, 2007). The reinforcement (US, chocolate rice cereal placed at the bottom of the opening in the target sponge) was associated with the same odor across trials (CS + ), and the rewarded odor was randomly assigned to each rat in a counterbalanced manner.…”

“…The training apparatus and behavioral procedures are explained elsewhere (Carballo-Marquez et al, 2007). The training apparatus was a 60 x 60 x 40cm square box containing three sponges (8.5 x 6.5 x 5.5cm) with a 3-cm diameter hole cut into the center to a depth of 2.5cm, placed in glass slide-holders of the same size.…”

“…To rule out olfactory impairments due to the infusion of DCS, an additional olfactory perception test was conducted at the end of each experiment (Carballo-Marquez et al, 2007;QuirozPadilla, Guillazo-Blanch, Vale-Martinez & Marti-Nicolovius, 2006;Wrenn, Harris, Saavedra & Crawley, 2003). Twenty-four hours prior to the olfactory test, the rats were habituated to butterflavored cookies (Brambly Hedge, Denmark).…”