DPhaSUPFIG 7: Neuron processes in the isthmus.

A. Illustration showing the head and pharynx with region of TEM sections designated by an arrow.
B. Transverse TEM section in the isthmus of an L2 showing the left subventral nerve cords containing neuron process and a gland cell process. The NSM process at the basal membrane of the pharynx is indicated. (Image source: N2 L2 28-14 [D. Riddle] 1035.)
C. Transverse TEM section of a dauer pharynx in the isthmus region, also showing the left subventral nerve cord and an NSM process. (Image source: N2 starved dauer 50-2-2 [D. Riddle] 787.)
In B&C, NSM processes in basal positions form active zones pointing towards the pseudocoelom (see also PhaFIG 9F-H to see example of these zones in the adult). This anatomical feature led to the hypothesis that NSM neurons have neurohumoral roles and may influence other cells at a distance (Avery and Thomas, 1997). One such example is the role of NSM serotonerigic neurotransmission in the enhanced slowing response of food-deprived animals upon encountering a food source (Sawin et al, 2000).

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