Ects of Herpes simplex virus HSV on DRG neuron ion channels

HSV induces a selective loss of sodium currents in DRG neurons

Herpes simplex virus type 1 (HSV-1) is a common neurotropic virus that, in vivo, forms a latent infection in primary afferent neurons. HSV infection is associated with abnormal sensations around the site of initial infection including tingling, parasthesia, loss of touch and pain sensations (Andoh et al 1995) which have been

FIG. 4. (Top) Na+ currents evoked by voltage steps from — 80 mV to —10 mV in control (left) andHSV-infectedDRG neurons (right). (Bottom) Normalized (nA/pF) Na+current amplitudes with above voltage step in control (filled bar) and at various times after HSV (5 plaque forming units/cell) infection show dramatic loss at 24 h.

FIG. 4. (Top) Na+ currents evoked by voltage steps from — 80 mV to —10 mV in control (left) andHSV-infectedDRG neurons (right). (Bottom) Normalized (nA/pF) Na+current amplitudes with above voltage step in control (filled bar) and at various times after HSV (5 plaque forming units/cell) infection show dramatic loss at 24 h.

attributed to alterations in neuronal excitability. HSV infection of DRG neurons in vitro abolishes the excitability of most neurons, and the neurons that remain excitable show action potentials that are smaller in amplitude and longer in duration than normal (Fukuda & Kurata 1981, Mayer et al 1986). Studies of the effects of HSV-1 infection on voltage gated Na+ currents in vitro (Storey et al 1996) have shown that 24 h after HSV-1 infection a voltage step from — 80 mV to 10 mV evoked a current in only 28% of neurons and that the amplitude of the current in these neurons was smaller than in uninfected neurons (HSV: — 0.017 0.004 nA/ pF; control: —0.14 0.009 nA/pF; n = 84). Although no change in theNa+ current amplitude was noted over the first 2—20 h after infection, the Na+ current amplitude reduced rapidly and the reduction was maximal after 24 h of infection (Fig. 4). This loss of current was maintained until at least 48 h post-infection. No voltage-gated Na+ currents were unmasked with voltage steps to a wide range of potentials from even more negative holding potentials indicating that the absence of currents was not due to any change in the voltage sensitivity of activation or inactivation. The

Was this article helpful?

0 0

Post a comment