Fig. 4. (A) Consistency among the gastropods in the occurrence of protraction-phase
interneurones with axons ascending in the contralateral cerebro-buccal
connective. Planorbis group 1 interneurone
(Arshavsky et al., 1988a);
Lymnaea N1 interneurone (Elliott
and Benjamin, 1985a); Aplysia B34 interneurone
(Hurwitz et al., 1997). (B)
Variation between retraction-phase (N3) neurones in Lymnaea. The
anatomical variation shown is accompanied by physiological and pharmacological
variation: the tonic N3 fires many action potentials, each producing a short
excitatory postsynaptic potential on the B3 motoneurone, while the phasic N3
and OC cells fire transiently at the start of this phase. The phasic N3
neurone produces a long-lasting excitation of N3 and the OC an inhibition of
the B3 motoneurone. The OC (but not the other interneurones) uses octopamine
as its transmitter. Modified from Elliott and Benjamin
(1985a) and Vehovszky et al.
(1998).
