Neuronal organization of the utricular macula concerned with innervation of single vestibular neurons in the cat

We investigated whether cross-striolar inhibition, which may increase sensi tivity to linear acceleration, contributed to utricular (UT) afferent inner vation of single vestibular neurons (VNs). Excitatory and inhibitory postsy naptic potentials (EPSPs, IPSPs, respectively) were recorded from VNs after focal stimulation of the UT macula (M). From a total of 83 VNs, 25 (30%) n eurons received inputs from both sides of the UTM, and the response pattern s were opposite, i.e. cross-striolar inhibition was observed. In roughly 2/ 3 of these neurons, stimulation of the medial side of the UTM evoked EPSPs, while stimulation of the lateral side evoked IPSPs. In the remaining 1/3 n eurons, the response patterns were opposite. Thirty-two (39%) of the 83 neu rons received the identical pattern of inputs from both sides of the UTM: E PSPs in 26 neurons and IPSPs in six neurons. Twenty-six (31%) of the 83 neu rons received inputs from either the medial or the lateral side of the UTM. These findings suggest that cross-striolar inhibition existed in the UT sy stem, although it was not a dominant circuit that increased the sensitivity as in the saccular system [15]. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.