Photoinactivation of the giant neuropil glial cells in the leech Hirudo medicinalis: effects on neuronal activity and synaptic transmission

1996 ◽  
Vol 76 (5) ◽  
pp. 2861-2871 ◽  
Author(s):  
J. Schmidt ◽  
J. W. Deitmer
Keyword(s):  
Synaptic Transmission ◽  
Glial Cells ◽  
Neuronal Activity ◽  
Lucifer Yellow ◽  
Hirudo Medicinalis ◽  
Membrane Properties ◽  
Sensory Cells ◽  
Chemical Synapse ◽  
Segmental Ganglion ◽  
Retzius Cells

1. We studied the effects of photoinactivation of neuropil glial (NG) cells of the leech Hirudo medicinalis on neuronal activity and synaptic transmission. Each segmental ganglion contains two of these giant glial cells, which are electrically and dye coupled. 2. One of the two NG cells in an isolated segmental ganglion was filled with the dye Lucifer yellow (LY). Subsequent irradiation of the ganglion with laser light (440 nm) to photolyze LY caused irreversible depolarization of both NG cells. The NG cells that were filled with LY depolarized from -73 +/- 1.1 (SE) mV to -22 +/- 2.4 mV within 25 +/- 2.8 min of continuous irradiation (n = 22). The other NG cell, which was not directly filled with LY, depolarized with some delay. 3. Photoinactivation of the NG cells caused an irreversible depolarization of Retzius neurons and noxious (N) sensory cells by a mean of 14 mV (n = 36) and 9 mV (n = 24), respectively. In addition, the input resistance was reduced by 54% in Retzius cells and by 34% in N cells. Spikes could not be evoked in Retzius cells after the inactivation of the NG cells, either by intracellular current injection or by electrical nerve stimulation. Similarly, anterior pagoda neurons, annulus erector neurons, and the excitor neurons of the ventrolateral circular muscles became inexcitable. However, N cells, heart interneurons, and most of the heart motor neurons, touch cells, and pressure cells could still generate spontaneous or evoked action potentials. 4. Photoinactivation of the NG cells impaired the electrical connection between the two Retzius neurons. The electrical coupling was completely eliminated in six of eight cell pairs and reduced by 66% in two others. 5. Photoinactivation of the NG cells in the 3rd and 4th segmental ganglion caused a complete block of the chemical synapse between reciprocal inhibitory heart interneurons in these ganglia; the bursting rhythm either stopped or changed to a tonic activity, whereas inhibitory postsynaptic potentials could not be recorded in either heart interneuron anymore. 6. Laser irradiation alone had no effect on neuronal activity and synaptic transmission. Addition of glutathione (10 mM) and ascorbic acid (10 mM) to the saline to bind extracellular radicals that might be produced by the irradiation did not suppress the effects caused by photoinactivation of NG cells. 7. Elevation of bath K+ concentration to 12 mM, acidification of the saline to pH 5.5, and alkalinization to pH 8.5 for 6 min each did not mimick the effects on membrane properties of Retzius cells as produced by inactivation of NG cells. The results suggest some role of glial cells in the maintenance of neuronal activity and electrical and chemical synaptic transmission.

Steps in the development of chemical and electrical synapses by pairs of identified leech neurons in culture

1989 ◽  
Vol 236 (1284) ◽  
pp. 253-268 ◽  
Keyword(s):  
Synaptic Transmission ◽  
Electrical Coupling ◽  
The Other ◽  
Enzyme Treatment ◽  
Sensory Cells ◽  
Electrical Transmission ◽  
Retzius Cells ◽  
Chemical Synapses ◽  
P Cells ◽  
Chemical Transmission

Experiments have been made to follow the development of chemical and electrical transmission between pairs of leech neurons in culture. 1. The cell bodies of identified neurons were isolated from the CNS by suction after mild enzyme treatment, together with a length of the initial segment (or ‘stump’). The neurons tested were Retzius cells (R), annulus erector motoneurons (AE), Anterior pagoda cells (AP) and pressure sensory cells (P). Pairs of cells were placed together in various configurations, with different sites on their surfaces making contact. 2. When pairs of Retzius cells were apposed with their stumps touching, serotonergic, chemically mediated synaptic transmission became apparent before electrical transmission. By 2.5 h impulses in either of the two Retzius cells produced hyperpolarizing inhibitory potentials in the other. These potentials were reversed by raised intracellular CI and showed clear facilitation. The strength of chemical transmission between Retzius cells increased over the next 72 h. 3. After chemical transmission had been established, weak non-recti­fying electrical transmission became apparent between Retzius cells at about 24–72 h. By 4 days coupling became stronger and tended to obscure chemically evoked synaptic potentials. 4. When pairs of Retzius cells were aligned in culture with the tip of one cell stump touching the soma of the other, chemical transmission also developed rapidly. Transmission was, however, in one direction, from stump to soma. At later stages non-rectifying electrical coupling devel­oped as with stump-stump configuration. With the cell bodies of two Retzius cells apposed, electrical coupling developed after several days, before chemical transmission could be observed. 5. When Retzius and P cells were cultured with their stumps in con­tact, inhibitory chemical synaptic transmission developed within 24 h. Transmission was always in one direction, from Retzius to P cell. Electrical coupling of Retzius and P cells never occurred whatever the spatial relations of the cells to one another. 6. Annulus erector motoneurons, which contain ACh and a peptide resembling FMRFamide, first developed electrical coupling when the two stumps were in contact and then, later, bi-directional chemical transmission. Anterior Pagoda pairs placed stump-to-stump showed electrical connections. 7. Electronmicrographs revealed the presence of synaptic structures within24 h after Retzius-Retzius, Retzius-P or AE–AE stumps were apposed. 8. The specificity of connections between cultured cells was similar to that observed in earlier experiments. A marked difference was in the speed and reliability with which chemical synapses developed when stumps were in contact. The results show that the tip of a neuron represents a preferential site for the formation of chemical synapses.

Rapidly Deactivating AMPA Receptors Determine Excitatory Synaptic Transmission to Interneurons in the Nucleus Tractus Solitarius From Rat

1997 ◽  
Vol 78 (1) ◽  
pp. 82-91 ◽  
Author(s):  
Stefan Titz ◽  
Bernhard U. Keller
Keyword(s):  
Synaptic Transmission ◽  
Ampa Receptor ◽  
Decay Time ◽  
Ampa Receptors ◽  
Time Course ◽  
Nucleus Tractus Solitarius ◽  
Synaptic Cleft ◽  
Excitatory Synaptic Transmission ◽  
Membrane Properties ◽  
Time Constants

Titz, Stefan and Bernhard U. Keller. Rapidly deactivating AMPA receptors determine excitatory synaptic transmission to interneurons in the nucleus tractus solitarius from rat. J. Neurophysiol. 78: 82–91, 1997. Excitatory synaptic transmission was investigated in interneurons of the parvocellular nucleus tractus solitarius (pNTS) by performing patch-clamp experiments in thin slice preparations from rat brain stem. Stimulation of single afferent fibers evoked excitatory postsynaptic currents (EPSCs) mediated by glutamate receptors of the dl-α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA) and N-methyl-d-aspartate types. AMPA-receptor-mediated EPSCs displayed decay time constants of 3.5 ± 1.2 (SD) ms (13 cells), which were slow compared with EPSC decay time constants in neurons of the cerebellum or hippocampus. Slow EPSC decay was not explained by dendritic filtering, because the passive membrane properties of pNTS interneurons provided favorable voltage-clamp conditions. Also, the slowness of EPSC decay did not result from slow deactivation of AMPA receptors (0.7 ± 0.2 ms, 5 cells), which was investigated during rapid application of agonist to outside-out patches. Comparison of AMPA receptor kinetics with EPSC decay time constants suggested that the slow time course of EPSCs resulted from the prolonged presence of glutamate in the synaptic cleft.

Auditory sensory cells in hawkmoths: identification, physiology and structure

1999 ◽  
Vol 202 (12) ◽  
pp. 1579-1587 ◽  
Author(s):  
M.C. Göpfert ◽  
L.T. Wasserthal
Keyword(s):  
Neuronal Activity ◽  
Sensory Cell ◽  
Sensory Organ ◽  
Sensory Cells ◽  
Chordotonal Organ ◽  
Auditory Function ◽  
Sensory Structure ◽  
Ultrasonic Stimulation ◽  
Afferent Response

The labral pilifers are thought to contain auditory sensory cells in hawkmoths of two distantly related subtribes, the Choerocampina and the Acherontiina. We identified and analysed these cells using neurophysiological and neuroanatomical techniques. In the death's head hawkmoth Acherontia atropos, we found that the labral nerve carries the auditory afferent responses of a single auditory unit. This unit responds to ultrasonic stimulation with minimum thresholds of 49–57 dB SPL around 25 kHz. Ablation experiments and analyses of the neuronal activity in different regions of the pilifer revealed that the auditory afferent response originates in the basal pilifer region. The sensory organ was identified as a chordotonal organ that attaches to the base of the pilifer. This organ is the only sensory structure in the basal pilifer region and consists of a single mononematic scolopidium and a single sensory cell. In Choerocampina, a homologous scolopidium was also found and is probably the only sensory structure of the pilifer that might serve an auditory function. Since a pilifer chordotonal organ with only a single scolopidium has also been detected in a non-hearing hawkmoth species, hearing in the distantly related choerocampine and acherontiine hawkmoths presumably evolved from a single proprioceptive mechanoreceptor cell that is present in all hawkmoths.

scholarly journals Roles of glial cells in modulating synaptic transmission in the hippocampal synapses.

1994 ◽  
Vol 64 ◽  
pp. 123
Author(s):  
Yoshihisa Kudo ◽  
Kyoko Nakamura ◽  
Shunzo Kondo ◽  
Akihiko Ogura
Keyword(s):  
Synaptic Transmission ◽  
Glial Cells ◽  
Hippocampal Synapses

Ultrastructure of the organ of Bellonci in the hypogean isopod Stenasellus virei boui Magniez (Crustacea, Asellota)

1992 ◽  
Vol 70 (1) ◽  
pp. 129-135
Author(s):  
Adriana Pitzalis ◽  
Christian Juberthie
Keyword(s):  
Glial Cells ◽  
Basal Body ◽  
Spatial Arrangement ◽  
Central Core ◽  
Sensory Cells ◽  
The Core ◽  
Ultrastructural Morphology

The ultrastructure of the organ of Bellonci in the hypogean isopod Stenasellus virei boui was investigated. There are two organs located anterodorsally, one on each side of the cephalon. Each organ consists of a wall surrounding a cavity with a central core irregular in shape. The bordering wall contains some glial cells and the inner dendritic segments of 25–28 sensory cells, each one bearing two cilia. Each cilium has a typical 9 + 0 axoneme, a basal body, and a long straight ciliary root that is at a right angle to the basal body; the cilium branches out into tubules that usually contain 1 microtubule, occasionally 2 or more. The ciliary tubules are gathered in three or four long bundles and are not linked to the core. The ciliary connections appear to be both conical and cylindrical. The ultrastructural morphology (polarization of the cilia, spatial arrangement of the bundles and central core) suggests that this organ can record directional stimuli.

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