Hyperpolarizing dorsal root potentials recorded from single fibres of the dorsal root in the cat

In non-anaesthetized spinal cats hyperpolarizing dorsal root potentials (DRPs) were recorded from single fibres of the dorsal root. They were evoked by volleys in saphenous and quadriceps nerves activating group II muscle afferents and cutaneous A afferents. Hyperpolarizing DRPs were most frequently encountered in fibres originating from muscle receptors. Their frequency was lower in fibres from deep receptors, from low threshold mechanoreceptors and from mechanical nociceptors. The amplitude of hyperpolarizing DRP was related to the modality of fibres from which DRP was recorded. During conditioning the time course of depression of testing hyperpolarizing DRP recorded from muscle receptor fibres did not exceed 100 msec. Hyperpolarization produced by repetitive stimulation was maintained in muscle afferent fibres but subsided to zero in fibres from low threshold mechanoreceptors.