High-resolution scatchard analysis shows D1 receptor binding on pyramidal and nonpyramidal neurons

In order to better understand the mechanism of action of atypical antipsychotic drugs (APDs), it is important to clarify how the dopamine system is integrated within local corticolimbic circuits. Toward this end, a high-resolution (HR) Scatchard technique has been used to measure the relative density (Bmax) and affinity (Kd) of D1 receptors on large neurons (> 100 microm2), on small neurons (< 100 microm2), and in neuropil (NPL) of rat medial prefrontal cortex (mPFC) and to determine the laminar distribution of these receptors for each neuronal compartment. Using [3H] SCH23390 as a ligand, all Kd and Bmax values were found to be similar indicating that D1 receptor activity is not preferentially localized to either large or small neuronal subtypes in mPFC. The density of D1 receptor binding in all three compartments was found to be almost twice as great in layers V and VI, as compared to superficial layers II and III. These results suggest that the blockade of D1 receptors associated with some atypical APDs may involve both pyramidal and nonpyramidal neurons in the PFC.