The semi-intact recording paradigm. (A) Illustration depicting the recording locations for vestibular ganglia neurons. Data were recorded from either calyx terminals of dimorphic afferent endings or from vestibular neuron cell bodies in isolated vestibular ganglion explants. The cross section through the sensory epithelia shows three types of afferent terminals: bouton (a), calyx only (b), and dimorphic (c). Dimorphic terminals innervate both type I and type II hair cells and were present in both central and peripheral zones. All recordings from terminals were from calyces of dimorphic endings. (B) Differential interference contrast image of the apical surface of the utricle preparation. Dimorphic calyces were identified by their restricted neck regions at the apical surface (arrows). (C) A subset of terminals was filled with Lucifer yellow introduced via recording pipettes. The tissue was fixed and imaged using confocal microscopy. A three-dimensional reconstruction shows the complex branching pattern of a typical dimorphic terminal that connects several calyces and bouton endings. Boxes are 10-µm cubes. (D and E) Representative families of voltage-dependent currents recorded from dimorphic calyx terminals (D) and vestibular neuron cell bodies (E). Inward Na⁺ and outward K⁺ currents were recorded in response to 50-ms voltage steps that ranged between −124 mV and 96 mV in 10-mV increments. Both Na⁺ and K⁺ currents were larger in the cell body than in calyx terminals. The scale bars apply to both current families.