Dorsolateral frontal cortex and peripheral muscarinic receptors participation in the discriminative stimulus properties of scopolamine in rats.

Organisms are capable of making decisions based on their ability to discriminate between different stimuli. This principle is fundamental for the adaptation of organisms to their environment, by emitting appropriate behaviors based on a previously acquired discriminative process. The present study analyzed the participation of the peripheral nervous system, the M₁ muscarinic receptor subtype, as well as the contribution of the dorsolateral frontal cortex to discrimination process using scopolamine as discriminative stimulus. Male Wistar rats were trained to discriminate between scopolamine (1.0 mg/kg) and saline injections (i.p.) using a two-lever operant procedure. Once discrimination was acquired, generalization curves for scopolamine, methylscopolamine, pirenzepine, dorsolateral frontal cortex lesion and control conditions were obtained. Results showed that rats were able to discriminate and generalize its responses to different doses of scopolamine but not for methylscopolamine or pirenzepine, thus the data suggest that discriminative properties of scopolamine are processed in CNS and that the M₁ receptor does not participate in this process. Dorsolateral frontal cortex lesion did not produce any statistically significant difference in the generalization curve, which suggests that a system different from the dorsolateral prefrontal cortex may be responsible for the control of stimulus produced by scopolamine.