Transmission at the giant motor synapses of the crayfish

Voltage-Dependent Enhancement of Electrical Coupling by a Subthreshold Sodium Current

“…The mechanism underlying this voltage dependence remains unknown. Voltage-dependent changes of electrical coupling are generally attributed to voltage-dependent properties of the gap junction channels (Furshpan and Potter, 1959;Auerbach and Bennett, 1969;Giaume and Korn, 1983;Edwards et al, 1991). Here we show that the observed enhancement does not represent a property of the gap junctions themselves but rather a property of the nonsynaptic membrane of the presynaptic afferent.…”

“…dependent changes of electrical coupling rely on properties of the gap junction channels themselves (Furshpan and Potter, 1959;Auerbach and Bennett, 1969;Giaume and Korn, 1983;Edwards et al, 1991), voltage-dependent amplification of electrical coupling in club endings depends largely on the activation of nonlinear properties of the nonjunctional membrane. Interestingly, whereas in other systems long-lasting amplification of electrical coupling by noninactivating subthreshold Na ϩ currents allows synchronized firing within a time window larger than that predicted by the time course of the presynaptic action potential (Mann-Metzer and Yarom, 1999), the contrasting interaction of this current with repolarizing K ϩ currents reproduces closely the waveform of the coupling recorded at resting potential.…”

“…The strength of electrical transmission depends not only on the conductance of the gap junction channels but also on the electrical and geometrical characteristics of the coupled cells (Bennett, 1966(Bennett, , 1977, which are determined to a large extent by their morphology and membrane properties. Thus, in addition to the control of gap junctional conductance itself (Furshpan and Potter, 1959;Auerbach and Bennett, 1969;Piccolino et al, 1982;Lasater and Dowling, 1985;Yang et al, 1990;Pereda et al, 1992Pereda et al, , 1998, changes in the conductance of the nonjunctional membrane are known to have a profound impact on electrical coupling (Kandel and Tauc, 1966;Spira et al, 1976;Zipser, 1979). In the mammalian CNS, neuronal gap junctions are often localized between small dendritic processes of dissimilar size and shape (Llinás et al, 1974;De Zeeuw et al, 1995;Fukuda and Kosaka, 2000;Fukuda and Kosaka, 2003) where geometry may favor transmission in one direction or the other.…”

Mechanisms of post‐synaptic excitation in amphibian motoneurones.

“…Obviously, the conclusion about electrical coupling between dorsal root afferents and spinal motoneurones must lead to the proposal of the absence of a reversal potential for the dorsal root e.p.s.p.s resistant to Ca-lack (Bennett, 1972 (Watanabe & Grundfest, 1961) and giant motor synapses (Furshpan & Potter, 1959 (Shapovalov & Kurchavyi, 1974;Werman & Carlen, 1976 Properties of glutamate induced responses. Analysis of post-synaptic responses produced synaptically and by ionophorezed glutamate has not as yet been sufficient to prove the identity of this substance and the excitatory transmitter in the mammalian spinal cord (Curtis et al, 1972).…”

Papel das sinapses elétricas em crises epilépticas

“…11 Este trabalho pioneiro abriu caminho para muitos outros que estabeleceram a comunicação elétrica entre neurônios, a chamada de sinapse elétrica, como distinta da neurotransmissão química. 4 Subsequentemente, vários estudos demonstraram que as sinapses elétricas não estavam restritas a invertebrados, mas também podiam ser encontradas em vertebrados, incluindo os mamíferos.…”