Worm Breeder's Gazette 2(2): 32

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

The Anterior Nervous System of C. elegans

J. White, E. Southgate, N. Thomson, S. Brenner

The arrangement of internal hypodermal ridges with their associated 
basement membranes seems to confine nervous tissue to specific regions 
and may define the basic shape of such structures as the nerve ring.  
The body musculature is arranged in four quadrants each consisting of 
about 24 cells.  The first 4 cells in each quadrant receive their 
synaptic input solely from the nerve ring; the next four jointly from 
the nerve ring and ventral cord and the remainder solely from the 
ventral cord.  Muscle cells which receive their synaptic input from 
the nerve ring send out arms which at first run outside the nerve ring 
and then turn and enter the inside of the ring from the rear so as to 
lie next to the motor neurones which line the inner surface of the 
ring.  The muscle arms here sort themselves out into 8 groups, each 
quadrant being sub-divided into two rows.  There are nine classes of 
motor neurones in the nerve ring and each individual neurone synapses 
onto two adjacent muscle rows defining either a quadrant with a 90  
edge or one with a 45  edge.  Neurones in six of the classes cover 90  
quadrants; two of the classes have neurones that cover 45  quadrants 
and one class (the inner labial mechano-receptor which has 6 fold 
symmetry) has neurones which cover both.  The motor neurones can 
either themselves be sensory neurones or receive their synapses 
directly from separate sensory neurones or via interneurones.  Some 
interneurons seem to be specific to a particular type of receptor 
while others have a more generalized integrative role.