Fig.5. Spontaneous electrical activity in the VNCs of virus- infected silkworm larvae. The insects were infected with 10⁵p.f.u. and, at the indicated times post-infection, were dissected to yield intact VNCs and bathed in saline. The RV-infected larvae revealed either a partial paralysis (slow mobility, spasmodic local contractions of the integument at 40–45h.p.i.) or full paralysis (in contracted body shape, as in Fig.1, at 45–52 h.p.i.). Extracellular recording was performed using a suction electrode between the 6^th and 7^th abdominal ganglion and data were collected during 5min of continuous recording. (A) Frequency analyses in the form of inter-spike interval (ISI) distribution histograms for individual insects were averaged and median ISI values were calculated (arrows). The total number of spikes recorded from the RV-infected VNC when compared to the WV were 9888±1646 (N=5) and 5141± 855 (N=6), respectively, at 40–45h.p.i. and 11485±1075 (N=7) and 5112±633 (N=3), respectively, at 45–52h.p.i. (B) A representative spontaneous electrical activity recorded from an RV- (upper trace) or WV-infected (lower trace) VNC. Notice the occurrence of bursts (underlined) in the recording from RV-infected (upper trace) insects at 50h.p.i. when compared to the homogeneous-scattered pattern of activity recorded from WV-infected insects at 50h.p.i. (lower trace). For technical reasons the amplitudes in such extracellular recordings are of no functional significance.

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