Field potentials evoked in rat primary somatosensory cortex (SI) by impulses in cutaneous A beta- and C-fibres.
A projection of cutaneous C-afferent fibres to the contralateral primary somatosensory cortex (SI) was examined in the halothane-anaesthetized rat. Field potentials evoked by electrical stimulation of the right sural nerve were recorded at the surface of an intracortically within the left SI cortex. A late surface positive potential (latency 110-190 ms, mean 136 ms) was evoked by sural stimulation at a strength that activated A- and C-fibres. A selective anodal block of impulse conduction in A-fibres proximal to the stimulating electrodes showed that impulses in C-fibres generate the late potential also in the absence of a preceding A-fibre input. Stimulation of the sural nerve at two sites caused a shift in latency of the late potential corresponding to a conduction velocity of the primary afferent fibres of less than 1.0 m/s. The distribution of the C-fibre-evoked potential in SI was similar to that of the A beta-fibre evoked 'primary' potential suggesting that the investigated projection of cutaneous C-fibres to SI has a somatotopic organization.
D000200:Action Potentials; D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D005073:Evoked Potentials, Somatosensory; D008297:Male; D009412:Nerve Fibers / Q000502:physiology*; D009413:Nerve Fibers, Myelinated / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D011919:Rats, Inbred Strains; D012867:Skin / Q000294:innervation*; D013003:Somatosensory Cortex / Q000502:physiology*; D013497:Sural Nerve / Q000502:physiology