2‐deoxyglucose uptake in the cat spinal cord during sustained and habituated activity in the plantar cushion reflex pathway

Abstract

[¹⁴C]2‐deoxy‐D‐glucose (2‐DG) was administered intravenously to anesthetized cats during electrical stimulation of the plantar cushion (central foot pad). Afferent volleys and the efferent reflex were monitored by recording from the tibial nerve at the ankle. Plantar cushion stimulation at 3 HZ, 5 × threshold for 45 minutes led to a discrete region of increased 2‐DG uptake dorsomedially in the dorsal horn, predominantly in Rexed's laminae III and IV, ipsilateral to the stimulation. A less marked increase in labeling was also sometimes observed in the medial portion of lamina V. No labeling specific to stimulation was observed in the ventral horns. A control preparation, to determine the effects of surgical manipulations alone, confirmed that the labeling was indeed specific to the plantar cushion stimulation.A pattern of labeling identical to that seen during 3 Hz, 5 × threshold stimulation occurred when 2‐DG was administered during 10 Hz, 5 × threshold stimulation, after the reflex elicited by plantar cushion stimulation had completely habituated.The most straightforward interpretation of our results suggests that the increases in 2‐DG labeling produced by stimulation of the plantar cushion probably occurred in regions with heavy concentrations of axon collaterals of the primary afferent Aαβ fibers from the plantar cushion, at or near their sites of termination in the dorsal horn.