RESUMEN
Electric fish generate and sense electric fields for navigation and communication. These signals can be energetically costly to produce and can attract electroreceptive predators. To minimize costs, some nocturnally active electric fish rapidly boost the power of their signals only at times of high social activity, either as night approaches or in response to social encounters. Here we show that the gymnotiform electric fish Sternopygus macrurus rapidly boosts signal amplitude by 40% at night and during social encounters. S. macrurus increases signal magnitude through the rapid and selective trafficking of voltage-gated sodium channels into the excitable membranes of its electrogenic cells, a process under the control of pituitary peptide hormones and intracellular second-messenger pathways. S. macrurus thus maintains a circadian rhythm in signal amplitude and adapts within minutes to environmental events by increasing signal amplitude through the rapid trafficking of ion channels, a process that directly modifies an ongoing behavior in real time.
Asunto(s)
Ritmo Circadiano/fisiología , Señales (Psicología) , Gymnotiformes/fisiología , Activación del Canal Iónico/fisiología , Canales Iónicos/metabolismo , Conducta Social , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Hormona Adrenocorticotrópica/farmacología , Animales , Ritmo Circadiano/efectos de los fármacos , Venenos de Cnidarios/farmacología , AMP Cíclico/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Órgano Eléctrico/citología , Órgano Eléctrico/efectos de los fármacos , Órgano Eléctrico/fisiología , Activación del Canal Iónico/efectos de los fármacos , Melanocortinas/farmacología , Modelos Biológicos , Péptidos/farmacología , Canales de Potasio de Rectificación Interna/metabolismo , Transporte de Proteínas/efectos de los fármacos , Sodio/metabolismo , Vesículas Transportadoras/efectos de los fármacos , Vesículas Transportadoras/metabolismoRESUMEN
Weakly electric fish such as Sternopygus macrurus utilize a unique signal production system, the electric organ (EO), to navigate within their environment and to communicate with conspecifics. The electric organ discharge (EOD) generated by the Sternopygus electric organ is quasi-sinusoidal and sexually dimorphic; sexually mature males produce long duration EOD pulses at low frequencies, whereas mature females produce short duration EOD pulses at high frequencies. EOD frequency is set by a medullary pacemaker nucleus, while EOD pulse duration is determined by the kinetics of Na+ and K+ currents in the electric organ. The inactivation of the Na+ current and the activation of the delayed rectifying K+ current of the electric organ covary with EOD frequency such that the kinetics of both currents are faster in fish with high (female) EOD frequency than those with low (male) EOD frequencies. Dihydrotestosterone (DHT) implants masculinize the EOD centrally by decreasing frequency at the pacemaker nucleus (PMN). DHT also acts at the electric organ, broadening the EO pulse, which is at least partly due to a slowing of the inactivation kinetics of the Na+ current. Here, we show that chronic DHT treatment also slows the activation and deactivation kinetics of the electric organ's delayed rectifying K+ current. Thus, androgens coregulate the time-varying kinetics of two distinct ion currents in the EO to shape a sexually dimorphic communication signal.