The current results suggest that activation of M2 receptors in the LDTg suppresses the efficacy of both a natural and a drug reward. OxoSQ suppressed lever pressing for both cocaine and food in a dose-dependent manner, especially during the initial part of the PR schedule sessions (Figs 2 - 4). Lever pressing for cocaine was attenuated for a longer period in response to OxoSQ than was lever pressing for food pellets (compare Figs 2A and 3A). This difference is attributed to the different pattern of lever pressing for cocaine as opposed to food pellets in the absence of drug treatment. For example, cocaine rewards were acquired gradually throughout the first 3 hours of the session (see Fig 2A), whereas most of the pellet rewards were acquired within the first hour (see Fig 3A). Animals resumed their responding for cocaine or food as the effect of OxoSQ waned, which is reflected by lack of a significant effect on BPs for either cocaine or food. OxoSQ did not significantly compromise motor ability of the animals (Fig 5), and the non-significant locomotor stimulant
