Treatment with a muscarinic XXXX receptor antagonist impairs the acquisition of conditioned reward learning in @entity35 .

@entity35 @entity5591 @entity13635 @entity934
UNASSIGNED: The neural mechanisms whereby a reward-associated stimulus gains reinforcing properties and comes to function as a conditioned reward (CR) are not understood. We propose that muscarinic @entity934 (mACh) receptor stimulation is necessary for this type of learning. Here we tested the hypothesis that mACh receptor antagonism, with @entity5591 , would attenuate the acquisition by a food-related stimulus of the capacity to function as a CR. @entity35 were exposed to 5 pre-exposure sessions during which two levers were present, one producing a light and the other a tone when pressed. This was followed by 3 conditioning sessions in which the levers were absent and the @entity35 were presented with 30 light-food @entity13635 delivered randomly. In the test session, the levers were present and presses on both levers were recorded. Different groups of @entity35 received intraperitoneal injections of @entity5591 (0, 0.375, 0.75 and 1mg/kg) either prior to each conditioning session or prior to the test session. All groups showed significantly greater responding on the light lever in the test compared to the pre-exposure sessions, demonstrating the CR effect. In animals treated prior to conditioning the @entity5591 groups pressed significantly less on the light lever than the vehicle group. In animals treated prior to the test the increased lever pressing for light was similar for all groups. These data suggest that @entity5591 impaired the acquisition of CR but not its expression. The results support the hypothesis that mACh receptor stimulation is important for the acquisition by reward-associated stimuli of the ability to function as CRs.
