GABA_A channels are ubiquitously expressed on neuronal cells and act via an inward chloride current to hyperpolarize the cell membrane of mature neurons. Expression and function of GABA_A channels on airway smooth muscle cells has been demonstrated in vitro. Airway smooth muscle cell membrane hyperpolarization contributes to relaxation. We hypothesized that muscimol, a selective GABA_A agonist, could act upon endogenous GABA_A channels expressed on airway smooth muscle to attenuate induced increases in airway pressures in anesthetized guinea pigs in vivo. In an effort to localize muscimol's effect to GABA_A channels expressed on airway smooth muscle, we pretreated guinea pigs with a selective GABA_A antagonist (gabazine) or eliminated lung neural control from central parasympathetic, sympathetic and non-adrenergic, non-cholinergic (NANC) nerves before muscimol. Pretreatment with intravenous muscimol alone attenuated i.v. histamine-, i.v. acetylcholine- or vagal nerve stimulated-increases in peak pulmonary inflation pressure. Pretreatment with the GABA_A antagonist gabazine blocked muscimol's effect. Following the elimination of neural input to airway tone by central parasympathetic nerves, peripheral sympathetic nerves, and non-adrenergic, non-cholinergic nerves intravenous muscimol retained its ability to block i.v. acetylcholine-induced increases in peak pulmonary inflation pressures. These findings demonstrate that the GABA_A agonist muscimol acting specifically via GABA_A channel activation attenuates airway constriction independent of neural contributions. These findings suggest that therapeutics directed at the airway smooth muscle GABA_A channel may be a novel therapy for airway constriction following airway irritation and possibly more broadly in diseases such as asthma and COPD.