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1. Mild hypoxia exposure impacts peripheral serotonin uptake and degradation in Gulf toadfish ( Opsanus beta )

   https://doi.org/10.1242/jeb.244064  

   Sebastiani, John ; Sabatelli, Allyson ; McDonald, M. Danielle ( July 2022 , Journal of Experimental Biology)

   ABSTRACT Plasma serotonin (5-hydroxytryptamine, 5-HT) homeostasis is maintained through the combined processes of uptake (via the 5-HT transporter SERT, and others), degradation (via monoamine oxidase, MAO) and excretion. Previous studies have shown that inhibiting SERT, which would inhibit 5-HT uptake and degradation, attenuates parts of the cardiovascular hypoxia reflex in gulf toadfish (Opsanus beta), suggesting that these 5-HT clearance processes may be important during hypoxia exposure. Therefore, the goal of this experiment was to determine the effects of mild hypoxia on 5-HT uptake and degradation in the peripheral tissues of toadfish. We hypothesized that 5-HT uptake and degradation would be upregulated during hypoxia, resulting in lower plasma 5-HT, with uptake occurring in the gill, heart, liver and kidney. Fish were exposed to normoxia (97.6% O2 saturation, 155.6 Torr) or 2 min, 40 min or 24 h mild hypoxia (50% O2 saturation, ∼80 Torr), then injected with radiolabeled [3H]5-HT before blood, urine, bile and tissues were sampled. Plasma 5-HT levels were reduced by 40% after 40 min of hypoxia exposure and persisted through 24 h. 5-HT uptake by the gill was upregulated following 2 min of hypoxia exposure, and degradation in the gill was upregulated at 40 min and 24 h. Interestingly, there was no change in 5-HT uptake by the heart and degradation in the heart decreased by 58% within 2 min of hypoxia exposure and by 85% at 24 h. These results suggest that 5-HT clearance is upregulated during hypoxia and is likely driven, in part, by mechanisms within the gill and not the heart. 

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2. Serotonin immunoreactivity in the nervous system of the free-swimming larvae and sessile adult females of Stephanoceros fimbriatus (Rotifera: Gnesiotrocha)

   https://doi.org/10.1111/ivb.12102  

   Hochberg, Adele ; Hochberg, Rick ( December 2015 , Invertebrate Biology)

   null (Ed.)
3. The Sex-Specific VC Neurons Are Mechanically Activated Motor Neurons That Facilitate Serotonin-Induced Egg Laying in C. elegans

   https://doi.org/10.1523/JNEUROSCI.2150-20.2021  

   Kopchock, Richard J. ; Ravi, Bhavya ; Bode, Addys ; Collins, Kevin M. ( April 2021 , The Journal of Neuroscience)
4. Glutamate Electropolymerization on Carbon Increases Analytical Sensitivity to Dopamine and Serotonin: An Auspicious In Vivo Phenomenon in Mice?

   https://doi.org/10.1021/acs.analchem.0c04316  

   Holmes, Jordan ; Witt, Colby E. ; Keen, Deanna ; Buchanan, Anna Marie ; Batey, Lauren ; Hersey, Melinda ; Hashemi, Parastoo ( August 2021 , Analytical Chemistry)

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5. Serotonin signals through postsynaptic Gαq, Trio RhoGEF, and diacylglycerol to promote Caenorhabditis elegans egg-laying circuit activity and behavior

   https://doi.org/10.1093/genetics/iyac084  

   Dhakal, Pravat ; Chaudhry, Sana I. ; Signorelli, Rossana ; Collins, Kevin M. ; Pocock, ed., R. ( May 2022 , Genetics)

   Activated Gαq signals through phospholipase-Cβ and Trio, a Rho GTPase exchange factor (RhoGEF), but how these distinct effector pathways promote cellular responses to neurotransmitters like serotonin remains poorly understood. We used the egg-laying behavior circuit of Caenorhabditis elegans to determine whether phospholipase-Cβ and Trio mediate serotonin and Gαq signaling through independent or related biochemical pathways. Our genetic rescue experiments suggest that phospholipase-Cβ functions in neurons while Trio Rho GTPase exchange factor functions in both neurons and the postsynaptic vulval muscles. While Gαq, phospholipase-Cβ, and Trio Rho GTPase exchange factor mutants fail to lay eggs in response to serotonin, optogenetic stimulation of the serotonin-releasing HSN neurons restores egg laying only in phospholipase-Cβ mutants. Phospholipase-Cβ mutants showed vulval muscle Ca2+ transients while strong Gαq and Trio Rho GTPase exchange factor mutants had little or no vulval muscle Ca2+ activity. Treatment with phorbol 12-myristate 13-acetate that mimics 1,2-diacylglycerol, a product of PIP2 hydrolysis, rescued egg-laying circuit activity and behavior defects of Gαq signaling mutants, suggesting both phospholipase-C and Rho signaling promote synaptic transmission and egg laying via modulation of 1,2-diacylglycerol levels. 1,2-Diacylglycerol activates effectors including UNC-13; however, we find that phorbol esters, but not serotonin, stimulate egg laying in unc-13 and phospholipase-Cβ mutants. These results support a model where serotonin signaling through Gαq, phospholipase-Cβ, and UNC-13 promotes neurotransmitter release, and that serotonin also signals through Gαq, Trio Rho GTPase exchange factor, and an unidentified, phorbol 12-myristate 13-acetate-responsive effector to promote postsynaptic muscle excitability. Thus, the same neuromodulator serotonin can signal in distinct cells and effector pathways to coordinate activation of a motor behavior circuit.

    

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