Biphasic responses of the honeybee heart to nanomolar concentrations of amitraz

- The effects of amitraz were examined on the heart of honeybee ex vivo and in vivo.
- Amitraz induced biphasic effects, inhibition followed by acceleration.
- Inhibition of heart rate was due to hyperpolarization in cardiac potential.
- Excitation in heart rate was due to depolarization in cardiac potential.