Regional synthesis of neurotransmitter candidates in the CNS of the moth Manduca sexta

1. The ability of several defined structures in the central nervous system of the moth Manduca sexta to synthesize and store acetylcholine, γ-aminobutyric acid, 5-hydroxytryptamine, histamine, dopamine, norepinephrine, tyramine and octopamine was examined in pharate adults. With the exception of norepinephrine, synthesis and storage of all neurotransmitter candidates was detected in at least some structures. 2. The major sensory centers in the brain, the antennal and optic lobes, differ significantly in the spectrum of neurotransmitter candidates they appear able to synthesize and retain. The optic lobes can synthesize all neurotransmitter candidates examined, except norepinephrine, while the antennal lobes produce and store only acetylcholine, γ-aminobutyric acid, histamine and small amounts of tyramine. 3. Synthesis and storage of relatively large amounts of 5-hydroxytryptamine, dopamine and octopamine in segmental ganglia suggests a prominent role for these substances in the function of these ganglia. 4. Acetylcholine is produced and retained in greater quantities than all other neurotransmitter candidates, by nearly two orders of magnitude.