1. Whole cell patch-clamp experiments were conducted to determine whether rat aortic baroreceptor neurons contain mechanosensitive conductances. 2. Putative aortic baroreceptor neurons in the nodose ganglia were identified by injecting DiI onto the adventitia of the aortic arch. Nodose ganglia neurons were dissociated after ≥1 wk. A fluorescein-conjugated tetanus toxin fragment was used to confirm that the cells labeled with DiI in culture were neurons. 3. Hypoosmotic stretch significantly increased the conductance of DiI-labeled neurons (n = 19). The reversal potential of the response was -11 ± 1 (SE) mV. 4. In experiments on unlabeled neurons, only 7 of 13 cells showed increases in conductance. BC3H1 cells, a mouse tumor cell line, showed no changes in conductance. 5. Gadolinium (20 μM), a putative blocker of mechanosensitive channels, prevented the increase in conductance produced by hypoosmolality in seven of seven labeled cells. Equimolar concentrations of lanthanum (n = 6) and ω-conotoxin GVIA (1 μM, n = 4), which block voltage- gated calcium channels, failed to significantly affect the inward current.