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Serotonin‐caused phase shift of circadian rhythmicity in a photosensitive neuron
Author(s) -
RodríguezSosa Leonardo,
CalderónRosete Gabina,
Flores Gonzalo,
Porras M.G.
Publication year - 2007
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/syn.20425
Subject(s) - circadian rhythm , procambarus clarkii , serotonin , medicine , agonist , 5 ht receptor , endocrinology , receptor , crayfish , extracellular , immunocytochemistry , biology , chemistry , microbiology and biotechnology , ecology
In the sixth abdominal ganglion (sixth AG) of the crayfish, two photosensitive neurons are located and have been identified as caudal photoreceptors (CPRs). We have expanded our investigation on the role of 5‐Hydroxytryptamine (5‐HT) as a modulator of the spontaneous and light‐induced activity of the CPR. We located, by using immunocytochemistry, neurons in the sixth AG that contain the 5HT 1A receptor. The expression of these receptors was examined by binding assays with [ 3 H] 8‐hydroxy‐2 (di‐ n ‐propylamino) tetralin ([ 3 H(8‐OH‐DPAT). We examined the exogenous action of both 5HT and its agonist 8‐OH‐DPAT on the phase of circadian rhythms of the spontaneous electrical activity and the photoresponse of the CPR in the isolated sixth AG by conventional extracellular recording methods. Experiments were made on the adult crayfish Procambarus clarkii and Cherax quadricarinatus . Thirteen immunopositive neurons were located, principally near the ventral and dorsal surface of the sixth AG, with the mean diameter of their somata 20 ± 3 μm. The specific binding data showed the presence of 5‐HT 1A receptors with a mean level of 22.4 ± 6.6 fmol/mg of wet tissue. Spontaneous and light‐induced electrical activity of the CPR showed circadian variations with their activity more intense at night than in the day. Exogenous application of 5‐HT or 8‐OH‐DPAT causes a circadian phase‐shift in electrical activity of the CPR. Taken together, these results lead us to believe the 5‐HT acts as a modulator of circadian electrical activity of the CPR in the isolated sixth AG of crayfish. Moreover, it suggests that the 5‐HT 1A receptor participates in this modulation. Synapse 61:801–808, 2007. © 2007 Wiley‐Liss, Inc.