Kennedy G, Heiligenberg W
Neurobiology Unit, Scripps Institution of Oceanography, La Jolla, CA 92093-0202.
J Comp Physiol A. 1994 Mar;174(3):267-80. doi: 10.1007/BF00240210.
The medullary pacemaker nucleus of Hypopomus triggers each electric organ discharge (EOD) by a single command pulse. It consists of electrotonically coupled 'pacemaker' cells, which generate the rhythm, and 'relay' cells, which follow the pacemaker cells and excite the spinal motoneurons of the electric organ. The pacemaker cells receive two inputs from the complex of the diencephalic prepacemaker nucleus (PPn), a GABA-ergic inhibition and a glutamatergic excitation. Relay cells, on the other hand, receive two glutamatergic inputs, one from a subnucleus of the PPn, the PPn-C, and a second from the sublemniscal prepacemaker nucleus (SPPn). We have labelled afferents to the pacemaker nucleus by injecting HRP to specific sites of the prepacemaker complex. By using immunogold-labelled antibodies and en-grid staining techniques, we demonstrated GABA and glutamate immunoreactivity in labelled synaptic profiles of ultra-thin sections of the pacemaker nucleus. The two types of synapses were interspersed on the surfaces of pacemaker cells, with GABA-immunoreactive synapses apparently representing the GABA-mediated input of the 'PPn-I', an inhibitory subdivision of the PPn, and glutamate-immunoreactive synapses representing the input of the 'PPn-G', an excitatory subdivision of the PPn. Only glutamate-immunoreactive synapses were found on relay cells.
Hypopomus的延髓起搏核通过单个指令脉冲触发每个电器官放电（EOD）。它由电紧张耦合的“起搏”细胞和“中继”细胞组成，“起搏”细胞产生节律，“中继”细胞跟随起搏细胞并兴奋电器官的脊髓运动神经元。起搏细胞从间脑前起搏核（PPn）复合体接收两种输入，一种是GABA能抑制，另一种是谷氨酸能兴奋。另一方面，中继细胞接收两种谷氨酸能输入，一种来自PPn的一个亚核PPn-C，另一种来自亚丘脑前起搏核（SPPn）。我们通过将HRP注射到前起搏复合体的特定部位来标记到起搏核的传入纤维。通过使用免疫金标记抗体和电子网格染色技术，我们在起搏核超薄切片的标记突触轮廓中显示了GABA和谷氨酸免疫反应性。这两种类型的突触散布在起搏细胞表面，GABA免疫反应性突触显然代表PPn的抑制性细分“PPn-I”的GABA介导输入，而谷氨酸免疫反应性突触代表PPn的兴奋性细分“PPn-G”的输入。在中继细胞上仅发现谷氨酸免疫反应性突触。
