Octopaminergic system in the central nervous system of the terrestrial slug Limax

Abstract

The terrestrial slug Limax can learn to avoid the odor of some food (e.g., carrot juice) by the simultaneous presentation of an aversive stimulus (e.g., bitterness of quinidine). This type of associative memory critically depends on the higher olfactory center, the procerebrum in the central nervous system. The modulation of the local field potential (LFP) oscillation recorded on the procerebrum has been thought to reflect the information processing of the odor that elicits the behavioral change, such as avoidance of the aversively learned odor or approaching an attractive food's odor. Here we focused on octopamine, an important neuromodulator involved in learning and memory in invertebrates, and considered to be the invertebrate equivalent of noradrenaline. We identified a few octopaminergic neurons in the subesophageal and buccal ganglia, and a larger number near the procerebrum in the cerebral ganglia, using immunohistochmical staining and in situ hybridization of tyramine β-hydroxylase, an octopamine-synthesizing enzyme. Application of octopamine reduced the frequency of LFP oscillation in a dose-dependent manner, and this effect was inhibited by preincubation with phentolamine. High-performance liquid chromatography analysis revealed the presence of octopamine, noradrenaline, and adrenaline in the central nervous system. Unexpectedly, noradrenaline and adrenaline both accelerated the LFP oscillation, in contrast to octopamine. Our results suggest that octopamine and noradrenaline have distinct functions in olfactory information processing, in spite of their structural similarity. J. Comp. Neurol. 524:3849-3864, 2016. © 2016 Wiley Periodicals, Inc.

RFamidergic neurons in the olfactory centers of the terrestrial slug Limax

“…There are also other neurotransmitters that affect the oscillatory activity of the LFP in the PC, such as serotonin, dopamine, Phe-Met-Arg-Phe-NH 2 (FMRFamide or FMRFa), histamine, octopamine, and noradrenaline, that change the oscillatory frequency when applied exogenously to the brain in vitro [ 18 , 32 , 45 , 46 ]. Although many of these neurotransmitters send projections from outside of the PC, FMRFa is unique in that FMRFa-immunoreactive (FMRFa-IR) cell bodies have been identified both within and outside the PC [ 8 , 32 ].…”

Regional expression of neuropeptides in the retina of the terrestrial slug Limax valentianus (Gastropoda, Stylommatophora, Limacidae)

“…However, histamine and octopamine were not detected in the eye of Limax in our previous studies (Matsuo, Fukata, Kumagai, Kobayashi & Matsuo, 2016b;Matsuo et al, 2016b). Histamine has also been reported to be absent from the eye of Hermissenda (Webber et al, 2017).…”