PVQ is a pair of interneurons with cell bodies in the lumbar ganglia. Processes enter the posterior extremity of the ventral cord via the lumbar commissures; initially, both run anteriorly on the right-hand side of the hypodermal ridge. When the end of the pre-anal ganglion is reached, PVQL crosses over to the left-hand side of the hypodermal ridge and runs all the way along the ventral cord up to the nerve ring in this position, whereas PVQR runs on the right-hand side along with most of the processes of the ventral cord (figure 15). As the ring is approached, the processes move up to the dorsal surface of the neuropile of the ventral ganglion. The processes then run round each side of the ring, near the posterior face, in close association with the processes of ASJ. They meet and terminate on the dorsal mid-line; there is a gap junction at the point of contact on the JSH series but the two processes do not quite touch on the N2U series. The processes of PVQ have prominent lateral (b, c) and dorsal (d) vesicle-filled varicosities. There are many dark vesicles present in these regions; the rest of the cytoplasm stains rather lightly, giving the processes of PVQ a characteristic appearance (BDU looks similar but has smaller processes with fewer vesicles). The main synaptic output is to AIA (a, b, c, d), sometimes in dyadic combination with ASK (b, c). There are also a few minor synapses to AVF and HSN. The synaptic input is almost exclusively from ASJ (*a), in the nerve ring. There are gap junctions to ASK (*a, b) and ADA. There are practically no synapses of any consequence in the ventral cord, except possibly for a few synapses from PHA (*b) in the tail. Magnifications: (a) x 25500, (b-d) x 17000.
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Web adaptation, Thomas Boulin, for Wormatlas, 2001, 2002