Chlorzoxazone and baclofen reduce dendritic hyperexcitability in ATXN1[82Q] mice by activating subthreshold‐activated potassium channels. (A) Representative trace of dendritic calcium spikes from a wild‐type Purkinje neuron, (B) ATXN1[82Q] Purkinje neuron at baseline, and (C) the same ATXN1[82Q] Purkinje neuron treated with chlorzoxazone (50 μmol/L) and baclofen (2 μmol/L). (D) SKA‐31 (10 μmol/L) does not reduce dendritic hyperexcitability in ATXN1[82Q] Purkinje neurons (P = 0.376). (E) Chlorzoxazone (50 μmol/L) reduces dendritic hyperexcitability in ATXN1[82Q] Purkinje neurons (P = 0.025). (F) Chlorzoxazone (50 μmol/L) and baclofen (2 μmol/L) coadministration further reduces dendritic excitability in ATXN1[82Q] Purkinje neurons (P < 0.001). (G) Barium (50 μmol/L) occludes the effect of chlorzoxazone on dendritic excitability (P = 0.778). (H) Barium (500 μmol/L, P = 0.012), U73122 (10 μmol/L in recording pipette, P = 0.014), and TEA (1 mmol/L, P = 0.009) do not occlude the effect of baclofen on dendritic excitability, but cesium chloride (140 mmol/L in the recording pipette) does occlude the effect of baclofen on dendritic excitability (P = 0.356) in ATXN1[82Q] Purkinje neurons. *P < 0.05, **P < 0.01, ***P < 0.001, paired Student's t‐test. CHZ, chlorzoxazone.