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 (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 egg-laying. 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.