Serotonin modulation of caudal photoreceptor in crayfish

Serotonin modulation of caudal photoreceptor in crayfish

The sixth abdominal ganglion (6th AG) of the crayfish contains two photosensitive neurons. This caudal photoreceptor (CPR) displays spontaneous electrical activity and phasic–tonic responses to light pulses. In this paper, we analyzed the presence of serotonin in the 6th AG and its effects in the mo...

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Bibliographic Details
Published in:Comparative biochemistry and physiology. Toxicology & pharmacology Vol. 142; no. 3-4; pp. 220 - 230
Main Authors: Rodríguez-Sosa, Leonardo, Calderón-Rosete, Gabina, Villalobos, Mercedes Graciela Porras, Mendoza Zamora, Elena, González, Víctor Anaya
Format: Journal Article
Language:English
Published: United States Elsevier Inc 01-03-2006
Subjects:
5-Hydroxytryptamine
5-Hydroxytryptophan
Abdomen
Animals
Antibodies - immunology
Aromatic l-amino acid decarboxylase
Astacoidea - drug effects
Astacoidea - physiology
Cambaridae
Cherax quadricarinatus
Electrophysiology
Female
Ganglia, Invertebrate - drug effects
Ganglia, Invertebrate - physiology
l-Tryptophan
Male
Methysergide
Methysergide - pharmacology
Neuromodulator
Neurotransmitter
Photoreceptor Cells, Invertebrate - drug effects
Photoreceptor Cells, Invertebrate - physiology
Procambarus clarkii
Serotonin - pharmacology
Serotonin - physiology
Tryptophan hydroxylase
Tryptophan hydroxylase
5-Hydroxytryptamine
Neuromodulator
l-Tryptophan
Neurotransmitter
5-Hydroxytryptophan
Aromatic l-amino acid decarboxylase
Cherax quadricarinatus
Procambarus clarkii
Methysergide
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Summary:The sixth abdominal ganglion (6th AG) of the crayfish contains two photosensitive neurons. This caudal photoreceptor (CPR) displays spontaneous electrical activity and phasic–tonic responses to light pulses. In this paper, we analyzed the presence of serotonin in the 6th AG and its effects in the modulation of the activity of CPR. In the first part of our study, we identified serotonergic neurons in the 6th AG by immunostaining using an antibody against serotonin. Next, we quantified the serotonin contents in the 6th AG by using liquid chromatography. Finally, we searched for serotonergic modulation of the CPR electrical activity by using conventional extracellular recordings. We found 13 immunopositive neurons located in the ventral side of the 6th AG. The mean diameter of their somata was 23±9 μm. In addition, there was immunopositive staining in neuropilar fibers and varicosities. The contents of serotonin and its precursors in the 6th AG varied along the 24-h cycle. Its maximum value was reached by midday. Topic application of serotonin to ganglia kept in darkness increased the CPR spontaneous firing rate and reduced its light responsiveness. Both effects were dose-dependent within ED50∼1 μM and were blocked by the 5-HT antagonist methysergide. These observations support the role of serotonin as a neurotransmitter or neuromodulator in the CPR of the two species of crayfish Procambarus clarkii and Cherax quadricarinatus.
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ISSN:1532-0456
1878-1659
DOI:10.1016/j.cbpc.2005.10.006