Acetylcholine Release and Choline Uptake by Cuttlefish (Sepia officinalis) Optic Lobe Synaptosomes

Abstract

Acetylcholine (ACh), which is synthesized from choline (Ch), is believed to hold a central place in signaling mechanisms within the central nervous system (CNS) of cuttlefish (Sepia officinalis) and other coleoid cephalopods. Although the main elements required for cholinergic functionCuttlefish, like other coleoid cephalopods, has been the subject of many neurobiological studies. Although the functional anatomy of the cuttlefish nervous system has been well illustrated, including investigation by electrical stimulation (1, 2), much less information is available on signaling mechanisms within the neural networks of cephalopods (3).The CNS of cuttlefish consists of distinct but interconnected lobes, of which the paired optic lobes correspond to more than half (4). The cuttlefish optic lobe comprises an outer granule cell layer, a neurophil layer, an inner granule cell layer (the outer cortex), and numerous clusters of cell bodies separated by areas of nerve fibers and synaptic areas (the central medulla) (5). The optic lobes contain a repertoire of neuronal circuits, which integrate the central visual processing, visuomotor, learning and memory systems (6). ACh has been suggested to mediate neuronal signaling at the CNS of cuttlefish, given that the Koelle-Friedenwald stain revealed a neuropilar localization of the reaction of cholinesterases (7). Moreover, it has been shown that ACh catabolism increases in the optic lobes as a response to memory formation with a long-term retention delay (8). Additionally, the optic lobes, in which nicotinic-like receptors are widely present (9), are among the cuttlefish CNS regions with the highest levels of enzyme activity responsible for the synthesis (choline acetyltransferase) and degradation (acetylcholinesterase) of ACh (10). Furthermore, recent work on cuttlefish optic lobe slices (11) has shown that mecamylamine hydrochloride, a nicotinic receptor antagonist, blocks excitatory postsynaptic currents, which are due to spontaneously released ACh. As far as we know, our recent paper (12) was the first to provide a brief insight into the release of ACh and the uptake of its precursor (Ch) in cuttlefish optic lobe. The present study further characterizes

Induction of Invertebrate Larval Settlement; Different Bacteria, Different Mechanisms?

“…Numerous studies on the settlement of barnacle cyprid larvae focus on a “settlement-inducing protein complex” or SIPC secreted onto surfaces by conspecific barnacles and their cyprids 24 . Other studies on barnacle settlement also cite the requirement of bacterial films, even for the same barnacle species, Amphibalanus amphitrite 16 25 26 27 28 . These results may reflect the presence of multiple settlement cues for barnacle larvae 29 .…”

Immunolocalization of choline acetyltransferase of common type in the central brain mass of Octopus vulgaris

“…One type appears to depend on the postsynaptic response, while the other does not require a strong postsynaptic response for induction. 64 Our results could suggest that, like serotonin, 21 ACh may act as a neuromodulator in a reinforcing/reward signaling system. These findings reinforce the conclusion that the octopus vertical lobe and the vertebrate hippocampus seem to show a striking example of evolutionary convergence, so the CNS of cephalopods will improve our understanding of the evolution of such associative systems.…”

“…15–18 Cephalopod CNS have been shown to contain the same major neurotransmitters that are found in the mammals' brains 19 and it may be possible to use immunohistochemistry to define those areas of the cephalopod CNS that are analogous to neural regions in mammals. 20,21 …”