Muscimol is a potent agonist of inhibitory GABAA-receptors, which are a heterogenous family of pentameric complexes. Muscimol is considered to bind to all receptor subtypes at the orthosteric β+/α- interface. In one of our recent publications, we observed that the antipsychotic drugs clozapine (CLZ), loxapine (LOX) and chlorpromazine (CPZ) showed diverging results in displacing 3H-muscimol. While a complete displacement could be observed by bicuculline (BIC), and no displacement with CPZ, the compounds CLZ and LOX could only incompletely compete with the radioligand. In addition, the dose-response curves displayed a non-sigmoidal form, indicating that they are not following a standard one-site binding pharmacology. In the current study we now aimed to investigate more extensively the heterogeneity of BIC, CLZ, LOX and CPZ sensitive muscimol sites in rat brain. We tested membranes from four different brain regions and incubated them with 3H-muscimol and the four different compounds. We observed a unique pharmacology of each compound. Experiments on recombinantly expressed receptors indicate, that BIC can displace 3H-muscimol from all tested receptors, while LOX and CLZ more potently compete with 3H-muscimol in α4β2 compared to α1β2 or α6β2-containing receptors, suggesting a subtype selectivity. Our experimental findings are supported by docking analysis, designed to find structural correlates of the observed diversity of muscimol sites that are present in brain tissue and recombinantly expressed receptor subtypes.These findings indicate that 3H-muscimol binding sites in rat brain are more heterogenous than previously thought, with different populations of receptors, which are CPZ, LOX or CLZ sensitive or insensitive.