Effect of A803467 (1 mg) (A & B) and two doses of mibefradil (C–F) on the responses of spindles to succinylcholine (200 μg), injected into the femoral artery, and to tendon stretch. Note that in A & B that femoral arterial injection of DMSO, the vehicle for A803467, had no effect on the spindles’ responses to either succinylcholine or to stretch. In contrast, injection of A803467 (1 mg) almost abolished these responses as well as baseline activity. Asterisks (*) represent significant differences between baseline discharge and responses to succinylcholine or stretch (p < 0.05). Asterisks (*) over horizontal brackets represent significant differences between the increase in discharge rate in response to succinylcholine or stretch before and after either vehicle (DMSO), A803467 or Mibefradil (p < 0.05).