Opposing actions of 5HT1A and 5HT2-like serotonin receptors on modulations of the electric signal waveform in the electric fish Brachyhypopomus pinnicaudatus.
Serotonin (5-HT) is an indirect modulator of the electric organ discharge (EOD) in the weakly electric gymnotiform fish, Brachyhypopomus pinnicaudatus. Injections of 5-HT enhance EOD waveform "masculinity", increasing both waveform amplitude and the duration of the second phase. This study investigated the pharmacological identity of 5-HT receptors that regulate the electric waveform and their effects on EOD amplitude and duration. We present evidence that two sets of serotonin receptors modulate the EOD in opposite directions. We found that the 5HT1AR agonist 8-OH-DPAT diminishes EOD duration and amplitude while the 5HT1AR antagonist WAY100635 increases these parameters. In contrast, the 5HT2R agonist alpha-Me-5-HT increases EOD amplitude but not duration, yet 5-HT-induced increases in EOD duration can be inhibited by blocking 5HT2A/2C-like receptors with ketanserin. These results show that 5-HT exerts bi-directional control of EOD modulations in B. pinnicaudatus via action at receptors similar to mammalian 5HT1A and 5HT2 receptors. The discordant amplitude and duration response suggests separate mechanisms for modulating these waveform parameters.
Allee
Susan J
SJ
Department of Biological Sciences, Florida International University, Miami FL 33199, USA. allee.sj@gmail.com
Markham
Michael R
MR
Salazar
Vielka L
VL
Stoddard
Philip K
PK
D000704:Analysis of Variance; D000819:Animal Communication; D000818:Animals; D004555:Electric Fish / Q000378:metabolism*; D004557:Electric Organ / Q000187:drug effects / Q000502:physiology*; D008297:Male; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D044348:Receptors, Serotonin, 5-HT2 / Q000378:metabolism*; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D018490:Serotonin Agents / Q000494:pharmacology; D012737:Sex Factors; D012919:Social Behavior; D012930:Social Dominance
D044348:Receptors, Serotonin, 5-HT2; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D058826:Serotonin 5-HT2 Receptor Agonists; D058830:Serotonin 5-HT2 Receptor Antagonists; D018490:Serotonin Agents; D044282:Receptor, Serotonin, 5-HT1A