Excitatory synaptic action in motoneurones

Intracellular Recording from the Giant Synapse of the Squid

“…The potential level, where the spike flares up out of the synaptic potential, shifts with hyperpoladzation towards higher membrane potential levels. The postsynaptic potential is either slightly altered or not altered in amplitude--in agreement with the results of Coombs, Eccles, and Fatt (1955) but in contrast to the condition reported by Fatt and Katz (1951), and Hagiwara and Watanabe (1954). If this finding is correct it suggests that in the present preparation, the synaptic potential does not represent a short circuit across the membrane or have an equilibrium potential at which its amplitude becomes zero.…”

“…In the motoneuron of the spinal cord Coombs, Eccles, and Fatt (1955) found no enhancement of e.p.s.p, amplitude. Fig.…”

Dopaminergic modulation of dye coupling between neurons in the core and shell regions of the nucleus accumbens

“…One technique that has been used in several vertebrate systems (Baker and Llinas, 197 1;Llinis et al, 1974;MacVicar and Dudek, 198 1;Taylor and Dudek, 1982;Grace and Bunney, 1983;Piccolino et al, 1984;Dudek and Snow, 1985;Cepeda et al, 1989) as an adjunct to dye coupling is based on physiological recordings, since this measure not only can supply an independent assessment of junctional conductance, but also can examine whether the coupling has a functional impact on the physiology of the neurons examined. Four separate physiological observations were made that are consistent with the presence of electrical coupling: (1) the presence of evoked spikelets that, unlike EPSPs (Coombs et al, 1955), repolarize faster than would be predicted for a passive decay derived from the membrane time constant; (2) the failure to collide the spikelets with synaptically evoked spike discharge, showing that the spikelets were not activated antidromically in the neuron recorded; (3) the 100% correlation between cells exhibiting coupling potentials with those neurons subsequently shown to be dye-coupled, and (4) the ability to block pharmacologically the activation of putative coupling potentials with drugs shown to interrupt dye coupling.…”

“…4). Thus, unlike the passive decay associated with synaptic events, the spikelets repolarized via an active process (Coombs et al, 1955;Grace and Bunney, 1983). In each neuron that displayed these spikelets or fast prepotentials, subsequent staining with Lucifer yellow revealed that the neurons also exhibited dye coupling (n = 5).…”

Cross-correlation analysis of neuronal activities.

“…Intracellular recording of post-synaptic potentials (PSPs) evoked by activation of presynaptic cells has revealed synaptic connectivity in terms of excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) [18]. A considerable range of shapes and sizes of PSPs has been suggested to correspond to the differences in the effectiveness of underyling synaptic connections.…”