Worm Breeder's Gazette 6(1): 38

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.

Octopamine in C. elegans

B. Horvitz, C. Trent, M. Chalfie, P. Evans

Octopamine (p-hydroxyphenylethanolamine) seems likely to be a common 
neurotransmitter in invertebrates.  To determine if octopamine is 
present in C.  elegans, extracts were prepared by sonication and 
assayed biochemically.  The assay used involves the transfer by 
phenylethanolamine N-methyltransferase of a radioactive methyl group 
from [3H]-methyl-S-adenosyl-L-methionine to octopamine to form [3H]-
synephrine (N-methyloctopamine), which is then selectively extracted 
and subjected to chromatography in a variety of solvents.  About 0.1  
g of octopamine are present per gm of C.  elegans tissue.  This level 
is similar to that of dopamine (Sulston et al., J.  Comp.  Neurol.  
163, 215, 1975); C.  elegans hermaphrodites have only eight 
dopaminergic neurons, suggesting that a similar number of 
octopaminergic neurons may be present.  The level of octopamine varies 
with both the temperature of growth (0.3  g/gm at 15 C; 0.1  g/gm at 
20 C; 0.05  g/gm.  at 25 C) and developmental stage (larvae have at 
least 5-10X less octopamine than adults).  Exogenous octopamine (10 
mg/ml) depresses egg-laying, suggesting that the adult-specificity of 
endogenous octopamine may be related to the adult-specific behavior of 
Octopamine levels have been determined for many behavioral mutants.  
None were octopamine-deficient, but a number of strains -- CB268 (unc-
41 V), CB204 (unc-33 IV) and CB15 (unc-28 IV) -- appear to overproduce 
octopamine.  We do not know if the abnormalities in coordination and 
octopamine levels in these strains result from the same mutations.
Many neurons have uptake systems that allow them to concentrate 
their own transmitters as well as closely related compounds.  
Norepinephrine is structurally similar to octopamine (octopamine lacks 
the 3-0H of norepinephrine) but, unlike octopamine, can be visualized 
histochemically by the technique of formaldehyde-induced fluorescence (
FIF).  Hoping to reveal octopaminergic cells, we have exposed animals 
to norepinephrine and examined their FIF.  In addition to the known 
dopaminergic neurons (dopamine is also closely related to 
norepinephrine), a pair of cells in the tail and, occasionally, a pair 
of (amphidial?) cells in the head accumulate exogenous norepinephrine.