Sex differences in and hormonal regulation of Kv1 potassium channel gene expression in the electric organ: Molecular control of a social signal

Few, William P.; Zakon, Harold H.

doi:10.1002/dneu.20305

Cited by 23 publications

(18 citation statements)

References 60 publications

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“…One of these genes, Kv1.2b, shows no difference in expression levels across individuals, while expression of Kv1.1a and Kv1.2a is inversely correlated with EOD duration. Treatment with steroid hormones that change EOD duration produce corresponding changes in expression levels of these genes (Few and Zakon, 2007). Voltagegated K + channels are formed as tetramers of channel subunits, either homotetramers of a single subunit or in heterotetramers where different subunits from the same family associate to form the functional channel.…”

Section: Molecular Regulationmentioning

confidence: 99%

Electrocyte physiology: 50 years later

Markham

2013

Journal of Experimental Biology

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SummaryWeakly electric gymnotiform and mormyrid fish generate and detect weak electric fields to image their worlds and communicate. These multi-purpose electric signals are generated by electrocytes, the specialized electric organ (EO) cells that produce the electric organ discharge (EOD). Just over 50years ago the first experimental analyses of electrocyte physiology demonstrated that the EOD is produced and shaped by the timing and waveform of electrocyte action potentials (APs). Electrocytes of some species generate a single AP from a distinct region of excitable membrane, and this AP waveform determines EOD waveform. In other species, electrocytes possess two independent regions of excitable membrane that generate asynchronous APs with different waveforms, thereby increasing EOD complexity. Signal complexity is further enhanced in some gymnotiforms by the spatio-temporal activation of distinct EO regions with different electrocyte properties. For many mormyrids, additional EOD waveform components are produced by APs that propagate along stalks that connect postsynaptic regions to the main body of the electrocyte. I review here the history of research on electrocyte physiology in weakly electric fish, as well as recent discoveries of key phenomena not anticipated during early work in this field. Recent areas of investigation include the regulation of electrocyte activity by steroid and peptide hormones, the molecular evolution of electrocyte ion channels, and the evolutionary selection of ion channels expressed in excitable cells. These emerging research areas have generated renewed interest in electrocyte function and clear future directions for research addressing a broad range of new and important questions.

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Section: Molecular Regulationmentioning

confidence: 99%

Electrocyte physiology: 50 years later

Markham

2013

Journal of Experimental Biology

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“…Evidence from our lab suggests that in the electrocyte, androgens act via transcriptional control of Kv genes, resulting in channels with different activation kinetics. Two genes of the Kv1 family (Kv1.1a and Kv1.2a) are expressed in higher levels in the EO of Sternopygus with high EOD frequencies, and these genes are down-regulated by the same DHT-implant protocol used in this study (Few and Zakon, 2007). One other gene, Kv1.1b, is not regulated by androgens, and its mRNA levels are constant across EOD frequency.…”

Section: Discussionmentioning

confidence: 91%

“…The fish were subsequently implanted intraperitoneally with, depending on the size of the fish, two to four DHT capsules (1.3 mg of DHT in 1 cm segment of Silastic tubing, the ends of which were then sealed with Silastic adhesive) or control capsules (empty 1 cm sealed Silastic tubing). Previous measurements with capsules of these dimensions indicate that they produce circulating levels of DHT of 1-10 ng/mL plasma (Few and Zakon, 2007). Fish were then returned to their aquaria.…”

Section: Experimental Designmentioning

confidence: 99%

Androgen modulates the kinetics of the delayed rectifying K⁺ current in the electric organ of a weakly electric fish

McAnelly

Zakon

2007

Developmental Neurobiology

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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.

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“…This alternate flow of current generates the characteristic biphasic B. gauderio waveform (Bennett, 1971). Variation in signal amplitude and duration is determined by the kinetics of the Na + and K + currents and the differential distribution of ion channels across the electrocyte membranes (Ferrari et al, 1995;Few and Zakon, 2001;Few and Zakon, 2007;Schaefer and Zakon, 1996).…”

Section: Neuroendocrine Regulation Of the Eod Waveformmentioning

confidence: 99%

Behavioral ecology, endocrinology and signal reliability of electric communication

Gavassa

Goldina

Silva

et al. 2013

Journal of Experimental Biology

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SummaryThe balance between the costs and benefits of conspicuous animal communication signals ensures that signal expression relates to the quality of the bearer. Signal plasticity enables males to enhance conspicuous signals to impress mates and competitors and to reduce signal expression to lower energetic and predation-related signaling costs when competition is low. While signal plasticity may benefit the signaler, it can compromise the reliability of the information conveyed by the signals. In this paper we review the effect of signal plasticity on the reliability of the electrocommunication signal of the gymnotiform fish Brachyhypopomus gauderio. We (1) summarize the endocrine regulation of signal plasticity, (2) explore the regulation of signal plasticity in females, (3) examine the information conveyed by the signal, (4) show how that information changes when the signal changes, and (5) consider the energetic strategies used to sustain expensive signaling. The electric organ discharge (EOD) of B. gauderio changes in response to social environment on two time scales. Two hormone classes, melanocortins and androgens, underlie the short-term and long-term modulation of signal amplitude and duration observed during social interaction. Population density drives signal amplitude enhancement, unexpectedly improving the reliability with which the signal predicts the signalerʼs size. The signalʼs second phase elongation predicts androgen levels and male reproductive condition. Males sustain signal enhancement with dietary intake, but when food is limited, they ʻgo for brokeʼ and put extra energy into electric signals. Cortisol diminishes EOD parameters, but energy-limited males offset cortisol effects by boosting androgen levels. While physiological constraints are sufficient to maintain signal amplitude reliability, phenotypic integration and signaling costs maintain reliability of signal duration, consistent with theory of honest signaling. on the reliability of the information conveyed by the signal. In this paper, we (1) discuss the endocrine mechanisms that regulate signal plasticity in males, (2) explore whether those mechanisms are also present in females, (3) examine the information conveyed by the signal, (4) examine how that information changes when the signal changes, and finally (5) consider the energetic strategies used to sustain expensive signaling.

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Sex differences in and hormonal regulation of Kv1 potassium channel gene expression in the electric organ: Molecular control of a social signal

Cited by 23 publications

References 60 publications

Electrocyte physiology: 50 years later

Electrocyte physiology: 50 years later

Androgen modulates the kinetics of the delayed rectifying K⁺ current in the electric organ of a weakly electric fish

Behavioral ecology, endocrinology and signal reliability of electric communication

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Sex differences in and hormonal regulation of Kv1 potassium channel gene expression in the electric organ: Molecular control of a social signal

Cited by 23 publications

References 60 publications

Electrocyte physiology: 50 years later

Electrocyte physiology: 50 years later

Androgen modulates the kinetics of the delayed rectifying K+ current in the electric organ of a weakly electric fish

Behavioral ecology, endocrinology and signal reliability of electric communication

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Androgen modulates the kinetics of the delayed rectifying K⁺ current in the electric organ of a weakly electric fish