Steroid influences upon the discharge frequencies of a weakly electric fish

Jh, Meyer

doi:10.1007/bf00610339

Cited by 86 publications

(69 citation statements)

References 26 publications

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“…Fish of both sexes were used based on the observation that males and females respond similarly to exogenous steroid treatment (Meyer, 1983). The availability of female fish was limited, and thus not all groups contained equal numbers of males and females.…”

Section: Methodsmentioning

confidence: 99%

“…1). Meyer (1983) first reported that E 2 increased EOD frequency, but this result was based on high doses of E 2 injected intraperitoneally, and the resulting plasma steroid concentrations were not measured. Our hormonal manipulation using implants more likely mimics the gradual rise in estrogens during natural ovarian recrudescence and produces concentrations that are within the physiological range of breeding female teleost fish (Fostier et al, 1983).…”

Section: Estrogen As a Modulator Of The Eodmentioning

confidence: 99%

“…EOD frequency varies inversely with plasma androgens in males during the natural breeding season (Zakon et al, 1991a,b), and in the laboratory, exogenous androgen [testosterone (T) and dihydrotestosterone] treatment lowers EOD frequency and broadens pulse duration (Meyer, 1983(Meyer, , 1984 Zakon et al, 1991a,b). It is not known how androgens alter the medullary neurons that control EOD frequency, but recent voltage-clamp studies on electrocytes show that androgens increase EOD pulse duration by causing the sodium current to inactivate more slowly (Ferrari and Zakon, 1993;Zakon, 1993;Ferrari et al, 1995).…”

Section: Abstract: Estrogen; Sodium Current; Electric Fish; Estrogenmentioning

confidence: 99%

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Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

1997

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Many species of electric fish emit sexually dimorphic electrical signals that are used in gender recognition. In Sternopygus, mature females produce an electric organ discharge (EOD) that is higher in frequency and shorter in pulse duration than that of mature males. EOD pulse duration is determined by ion currents in the electrocytes, and androgens influence EOD pulse duration by altering the inactivation kinetics of the electrocyte sodium current. We examined whether estrogen modulates the female-specific EOD and, if so, whether it regulates EOD pulse duration by acting on the same androgen-sensitive ion current in the electrocytes. We implanted gonadectomized Sternopygus with either empty SILASTIC capsules (control), one capsule filled with estradiol-17␤ (E 2 ; low dose), or three capsules of E 2 (high dose). Twelve days after implantation, E 2 -treated fish had plasma E 2 levels ϳ3.3-fold (low dose) or ϳ7.1-fold (high dose) higher than controls. After implantation, both E 2 -treated groups had higher EOD frequency and shorter EOD pulse duration than controls and their own preimplantation values. Through immunocytochemistry, we identified immunoreactive estrogen receptors in the nuclei of electrocytes, indicating that these cells are directly responsive to estrogen. In addition, voltage-clamp studies showed that E 2 affected the electrocyte ion currents kinetics: the sodium inactivation time constant was significantly lower in E 2 -treated fish than in controls. Thus, sexual dimorphism in the electrocommunication signal results, at least in part, from estrogens and androgens acting in opposite directions on the same ion current in the electrocytes. Key words: estrogen; sodium current; electric fish; estrogen receptor; electric organ; SternopygusIn most vertebrates, steroids have potent influences on the expression of sexually dimorphic reproductive behaviors such as courtship and mating (Kelley, 1988). Many studies have shown that regions of the nervous system and the effector organs that control reproductive behaviors have specific receptors for sex steroids, and more recently researchers have found that steroids can induce changes in the overall extracellular electrical activity in brain nuclei (Becker et al., 1992). Our understanding, however, of how steroids alter the electrical properties in specific, behaviorally relevant cells is still limited.Recent studies on the sexually dimorphic electrocommunication signal of a weakly electric fish, Sternopygus, have demonstrated that androgens alter specific ionic conductances in excitable cells involved in reproductive behavior (Ferrari and Zakon, 1993;Zakon, 1993;Ferrari et al., 1995). This has been possible because the neural circuits and effector cells underlying this behavior are relatively simple and discrete (Bullock and Heiligenberg, 1986), and some cells, the electrocytes of the electric organ, are large and accessible for recording changes in membrane properties by voltage clamp (Ferrari and Zakon, 1993;Ferrari et al., 1995;McAnelly and Zakon, 1996).In ...

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Section: Methodsmentioning

confidence: 99%

Section: Estrogen As a Modulator Of The Eodmentioning

confidence: 99%

Section: Abstract: Estrogen; Sodium Current; Electric Fish; Estrogenmentioning

confidence: 99%

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Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

1997

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“…This signal plasticity is driven by the slow, genomic action (daysweeks) of steroid hormones Zakon, 1993; and by the rapid, non-genomic (minutes-hours) action of monoamine and peptide hormones . Androgens masculinize the gymnotiform EOD by increasing waveform duration in peripheral electrocytes Bass and Hopkins, 1984; and altering discharge frequency in the central pacemaker nucleus Meyer, 1983).…”

Section: Introductionmentioning

confidence: 99%

“…However, in the genus Brachyhypopomus (Hypopomidae), the EOD changes on multiple timescales. Long-term changes occur during development and seasonally (Franchina, 1997), and are driven by steroid hormones (Meyer, 1983;Mills and Zakon, 1991;Zakon, 1993). Rapid changes, on the other hand, ranging from minutes to hours, occur during the onset of nighttime activity and social interactions Hagedorn, 1995;.…”

Section: The Eod Is Generated By a Well-described Neural Circuit Thatmentioning

confidence: 99%

Endocrine Regulation of Dynamic Communication Signals in Gymnotiform Fish

Goldina¹

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between an inconspicuous signal that evades predators and an extravagant signal preferred by females. Such a signal has been described in the gymnotiform electric fish, Brachyhypopomus gauderio, which produces a sexually dimorphic electric organ discharge (EOD). The EOD varies on a circadian rhythm and in response to social cues. This signal plasticity is mediated by the slow action of androgens and rapid action of melanocortins.My dissertation research tested the hypotheses that (1) signal plasticity is related to sociality levels in gymnotiform species, and (2) differences in signal plasticity are regulated by differential sensitivity to androgen and melanocortin hormones. To assess the breadth of dynamic signaling within the order Gymnotiformes, I sampled 13 species from the five gymnotiform families. I recorded EODs to observe spontaneous signal oscillations after which I injected melanocortin hormones, saline control, or presented the fish with a conspecific. I showed that through the co-option of the ancient melanocortin vii pathway, gymnotiforms dynamically regulate EOD amplitude, spectral frequency, both, or neither.To investigate whether observed EOD plasticities are related to species-specific sociality I tested four species; two territorial, highly aggressive species, Gymnotus carapo and Apteronotus leptorhynchus, a highly gregarious species, Eigenmannia cf. virescens, and an intermediate short-lived species with a fluid social system, Brachyhypopomus gauderio. I examined the relationship between the androgens testosterone and 11-ketotestosterone, the melanocortin α-MSH, and their roles in regulating EOD waveform.

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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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Steroid influences upon the discharge frequencies of a weakly electric fish

Cited by 86 publications

References 26 publications

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Endocrine Regulation of Dynamic Communication Signals in Gymnotiform Fish

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

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Steroid influences upon the discharge frequencies of a weakly electric fish

Cited by 86 publications

References 26 publications

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Estrogen Modifies an Electrocommunication Signal by Altering the Electrocyte Sodium Current in an Electric Fish,Sternopygus

Endocrine Regulation of Dynamic Communication Signals in Gymnotiform Fish

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

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