Neurotransmitter synthesis in Limulus ventral nerve photoreceptors

Radiochemical precursor compounds for neurotransmitters were incubated with Limulus ventral nerve photoreceptor preparations. Octopamine was preferentially synthesized by a photoreceptor rich fraction of the nerve, acetylcholine was made by a photoreceptor poor fraction, and gamma-aminobutyric acid was made about equally well in both fractions. The possibility that the ventral nerve photoreceptor cells serve a neurosecretory function in the adult Limulus is discussed.