Schaefer J e, Zakon H H
Department of Zoology and Center for Developmental Biology, The University of Texas at Austin, 78712, USA.
J Neurosci. 1996 Apr 15;16(8):2860-8. doi: 10.1523/JNEUROSCI.16-08-02860.1996.
The South American knifefish (Apteronotus leptorhynchus), or brown ghost, produces a high-frequency (600-1000 Hz) sinusoidal electric organ discharge (EOD) with males discharging at higher frequencies than females. In addition, each fish has a unique EOD frequency within the frequency range of its gender. The electromotor circuit responsible for EOD production consists of a medullary pacemaker nucleus (PMN) and spinal electromotor neurons (EMNs). In vitro spinal slice recording showed that, similar to the PMN, EMNs fire spontaneously at rates near the EOD frequency of each fish. The persistence of firing 2 weeks after high spinal transaction demonstrated that spontaneous firing rate was intrinsic to the EMNs and was not dependent on presynaptic input. We confirmed that 11-ketotestosterone (11 kT) raised and 17-beta-estradiol (E2) lowered the EOD frequency of intact fish. Because electromotor cells fire spontaneously near EOD, frequency, we investigated whether these steroids affect endogenous firing rates. Steroid implants were made in normal or spinally transected fish. Two weeks later, PMNs of normal fish and EMNs of transected fish were recorded in vitro. 11 kT increased and E2 decreased the intrinsic firing rate of neurons in the PMN and the EMNS. Hormones shifted the intrinsic firing rates of EMNS, although they were synaptically isolated during the hormone exposure.
南美刀鱼（Apteronotus leptorhynchus），即褐鬼刀鱼，会产生高频（600 - 1000赫兹）的正弦式电器官放电（EOD），雄性放电频率高于雌性。此外，每条鱼在其性别对应的频率范围内都有独特的EOD频率。负责产生EOD的电动回路由延髓起搏器核（PMN）和脊髓电动神经元（EMN）组成。体外脊髓切片记录显示，与PMN相似，EMN以接近每条鱼EOD频率的速率自发放电。高位脊髓横断2周后放电持续存在，表明自发放电速率是EMN固有的，不依赖于突触前输入。我们证实，11 - 酮睾酮（11 kT）提高而17 - β - 雌二醇（E2）降低完整鱼的EOD频率。由于电动细胞在EOD频率附近自发放电，我们研究了这些类固醇是否影响内源性放电速率。在正常或脊髓横断的鱼体内植入类固醇。两周后，在体外记录正常鱼的PMN和横断鱼的EMN。11 kT提高而E2降低了PMN和EMN中神经元的固有放电速率。激素改变了EMN的固有放电速率，尽管在激素暴露期间它们是突触隔离的。
