Abstract
We have recently reported that both non-noxious and noxious mechanical stimulation (brushing and pinching) of the ipsilateral hindpaw increases L4–6 dorsal spinal blood flow (SCBF) in anesthetized rats. In the present study we employed electro-acupuncture stimulation (EAS) with various frequencies and intensities for investigating contribution of Group II–IV afferent nerves to the SCBF responses. Regional spinal cord blood flow was measured with a laser Doppler flowmeter probe placed on the left dorsal surface of the spinal cord in the L4–6 regions. EAS was applied to the left hindpaw for 30 s at frequencies of 0.1- 100 Hz and at intensities of 0.05–10.0 mA. EAS (2 mA) above 0.5 Hz increased the SCBF in a frequency-dependent manner, reaching maximum increases at 20–50 Hz. On the other hand, the EAS (20 Hz) above 0.2 mA, threshold intensity of Group II afferents of the hindpaw, produced significant increases in the SCBF. With further increases in intensity up to 10 mA, larger increases in the SCBF were produced. The increases of SCBF were disappeared after severance of the dorsal roots. These results indicate that the SCBF responses to EAS of the ipsilateral hindpaw were dependent upon activation of sensory afferent nerves. Furthermore, it was demonstrated that increases in the SCBF were augmented by recruiting Group II, III and IV afferent nerves. [J Physiol Sci. 2008;58 Suppl:S159]
