The external Globus Pallidus (GPe) is a central hub in the basal ganglia. This structure is composed mainly of GABAergic neurons, which are divided into two distinct subtypes called: prototypic (70%) and arkypallidal (ARKY: 20%) neurons differentiated by their molecular and electrophysiological signatures. ARKY neurons project exclusively to the striatum and send a stop signal that interrupt ongoing action, suggesting their key role in movement control. However, little is known about the contribution of ARKY neurons to the pathophysiology of Parkinson’s Disease (PD). Moreover, it has been recently shown that ARKY neurons are the main recipients of bridging collaterals from striatal direct pathway neurons (dSTR), known to be hypoactive and hyperactive in parkinsonian and dyskinetic conditions, respectively. However, the properties of these bridging collaterals remains unknown under pathological conditions. The objective of this project is two-fold : 1/ to compare the excitability of ARKY neurons under control, parkinsonian (park) and dyskinetic (dysk) states, and 2/ to characterize GABAergic synaptic transmission of the bridging collaterals. Intrinsic excitability and GABAergic synaptic transmission of the dSTR-ARKY pathway were characterized using patch-clamp recordings. Our results show morpho-functional alterations of ARKY neurons under pathological conditions and decreased dSTR-ARKY transmission in dysk condition. In conclusion, our data suggested complex cellular and synaptic adaptation of ARKY neurons in PD and LID.