Figure 4. Glycogen supports CB sensory activity during periods of prolonged glucose deprivation.

A, glycogenolysis was targeted using a pharmacological inhibitor of glycogen phosphorylase: 4-dideoxy-1,4-imino d-arabinitol hydrochloride (DAB). Example traces of the sensory neuronal response to glucose deprivation are demonstrated in control CBs (upper) and in CBs treated with DAB (lower). Single fibre raw discharge was recorded and expressed in frequency histograms. Multiple action potentials have been overdrawn to show single fibre discrimination. B, mean data showing that DAB significantly decreased the time to a response in glucose-free stimulation. Error bars indicate + SEM; *P < 0.05 compared with the time to a response in the control group; unpaired t test (n = 14 fibres from 12 CB preparations–groups combined). C, example trace showing the response to a glucose-free stimulus following two 4–5 min episodes of severe hypoxia. Severe hypoxia was applied to cause functional depletion of glycogen (see text). Raw neuronal discharge is shown (upper) along with frequency (lower). Inset: multiple overdrawn action potentials demonstrating single fibre discrimination. D, mean data showing that one or two exposures to severe hypoxia significantly decreased the time taken to respond to subsequent glucose deprivation. Error bars indicate + SEM; *P < 0.05 compared with control group, ⁺P < 0.05 compared with the post single hypoxic episode group; one-way factorial ANOVA with Bonferroni post hoc analysis (n = 28 fibres from 19 CB preparations–groups combined).