Lateral ocellar nerve projections in the dragonfly brain

1978 ◽  
Vol 190 (1) ◽  
Author(s):  
RichardL. Chappell ◽  
LesleyJ. Goodman ◽  
J.Brian Kirkham
Keyword(s):  
Ocellar Nerve

Ultrastructural morphology of neurosecretory neurons in the barnacle Balanus amphitrite

1990 ◽  
Vol 48 (3) ◽  
pp. 434-435
Author(s):  
Grazia Tagliafierro ◽  
Cristiana Crosa ◽  
Marco Canepa ◽  
Tiziano Zanin
Keyword(s):  
Nervous System ◽  
Ultrastructural Level ◽  
Uranyl Acetate ◽  
Balanus Amphitrite ◽  
Neurosecretory Neurons ◽  
The Central Nervous System ◽  
Ultrathin Sections ◽  
Dense Core Granules ◽  
The Brain ◽  
Ocellar Nerve

Barnacles are very specialized Crustacea, with strongly reduced head and abdomen. Their nervous system is rather simple: the brain or supra-oesophageal ganglion (SG) is a small bilobed structure and the toracic ganglia are fused into a single ventral mass, the suboesophageal ganglion (VG). Neurosecretion was shown in barnacle nervous system by histochemical methods and numerous putative hormonal substances were extracted and tested. Recently six different types of dense-core granules were visualized in the median ocellar nerve of Balanus hameri and serotonin and FMRF-amide like substances were immunocytochemically detected in the nervous system of Balanus amphitrite. The aim of the present work is to localize and characterize at ultrastructural level, neurosecretory neuron cell bodies in the VG of Balanus amphitrite.Specimens of Balanus amphitrite were collected in the port of Genova. The central nervous system were Karnovsky fixed, osmium postfixed, ethanol dehydrated and Durcupan ACM embedded. Ultrathin sections were stained with uranyl acetate and lead citrate. Ultrastructural observations were made on a Philips M 202 and Zeiss 109 T electron microscopy.

scholarly journals Electrophysiology of the Insect Dorsal Ocellus

1961 ◽  
Vol 44 (3) ◽  
pp. 605-627 ◽  
Author(s):  
Philip Ruck
Keyword(s):  
Cell Layer ◽  
Receptor Cell ◽  
Photoreceptor Cells ◽  
Nerve Fibers ◽  
Spontaneous Discharge ◽  
Generator Potential ◽  
Nerve Impulses ◽  
Potential Component ◽  
Ocellar Nerve ◽  
State Component

Dorsal ocelli are small cup-like organs containing a layer of photoreceptor cells, the short axons of which synapse at the base of the cup with dendritic terminals of ocellar nerve fibers. The ocellar ERG of dragonflies, recorded from the surface of the receptor cell layer and from the long lateral ocellar nerve, contains four components. Component 1 is a depolarizing sensory generator potential which originates in the distal ends of the receptor cells and evokes component 2. Component 2 is believed to be a depolarizing response of the receptor axons. It evokes a hyperpolarizing postsynaptic potential, component 3, which originates in the dendritic terminals of the ocellar nerve fibers. Ocellar nerve fibers in dragonflies are spontaneously active, discharging afferent nerve impulses (component 4) in the dark-adapted state. Component 3 inhibits this discharge. The ERG of the cockroach ocellus is similar. The main differences are that component 3 is not as conspicuous as in the dragonflies and that in most cases ocellar nerve impulses appear only as a brief burst at "off." In one preparation a spontaneous discharge of nerve impulses was observed. As in the dragonflies, this was inhibited by illumination.

scholarly journals Neural Organization of the Median Ocellus of the Dragonfly

1972 ◽  
Vol 60 (2) ◽  
pp. 121-147 ◽  
Author(s):  
Richard L. Chappell ◽  
John E. Dowling
Keyword(s):  
Synaptic Transmission ◽  
Receptor Potential ◽  
Transient Responses ◽  
Slow Potential ◽  
Neural Organization ◽  
Postsynaptic Activity ◽  
Potential Activity ◽  
Median Ocellus ◽  
Ocellar Nerve

Intracellular responses from receptors and postsynaptic units have been recorded in the median ocellus of the dragonfly. The receptors respond to light with a graded, depolarizing potential and a single, tetrodotoxin-sensitive impulse at "on." The postsynaptic units (ocellar nerve dendrites) hyperpolarize during illumination and show a transient, depolarizing response at "off." The light-evoked slow potential responses of the postsynaptic units are not altered by the application of tetrodotoxin to the ocellus. It appears, therefore, that the graded receptor potential, which survives the application of tetrodotoxin, is responsible for mediating synaptic transmission in the ocellus. Comparison of pre- and postsynaptic slow potential activity shows (a) longer latencies in postsynaptic units by 5–20 msec, (b) enhanced photosensitivity in postsynaptic units by 1–2 log units, and (c) more transient responses in postsynaptic units. It is suggested that enhanced photosensitivity of postsynaptic activity is a result of summation of many receptors onto the postsynaptic elements, and that transients in the postsynaptic responses are related to the complex synaptic arrangements in the ocellar plexus to be described in the following paper.

scholarly journals CHARACTERISATION OF LARGE SECOND-ORDER OCELLAR NEURONES OF THE BLOWFLY CALLIPHORA ERYTHROCEPHALA

1994 ◽  
Vol 191 (1) ◽  
pp. 231-245 ◽  
Author(s):  
P Simmons ◽  
S Jian ◽  
F Rind
Keyword(s):  
Light Intensity ◽  
Response Curve ◽  
Compound Eye ◽  
Input Resistance ◽  
Membrane Resistance ◽  
Current Strength ◽  
Second Order ◽  
Calliphora Erythrocephala ◽  
Variable Amplitude ◽  
Ocellar Nerve

1. Blowflies have twelve large, second-order ocellar neurones (L-neurones) with axons in the single ocellar nerve. These neurones have fairly restricted arborizations in the posterior slope neuropile of the protocerebrum and cell bodies in the nerve, near to the fused ocellar retinae. 2. Like ocellar L-neurones of other insects, or large second-order neurones of the fly compound eye, blowfly L-neurones hyperpolarise in response to increases in light intensity and depolarise in response to decreases in light intensity. Both polarities of response have a strong phasic component. Adaptation to sustained illumination shifts the intensity­response curve, with little change in its gradient. 3. The maximum responses of blowfly L-neurones to sinusoidal changes in light intensity occur at stimulus frequencies of 5­10 Hz. 4. Hyperpolarising an L-neurone with small currents causes an increase in input resistance. Larger hyperpolarising currents cause oscillations in the membrane potential. The amplitude of the oscillations increases with current strength. Repolarisation generates brief rebound spikes of variable amplitude. 5. Injection of small hyperpolarising currents increases the amplitude of a response to a subsaturating pulse of light. This effect is not seen for saturating responses to light and is likely to be due to the increase in membrane resistance caused by hyperpolarisation.

scholarly journals Feedback synaptic interaction in the dragonfly ocellar retina.

1978 ◽  
Vol 71 (2) ◽  
pp. 157-175 ◽  
Author(s):  
A Klingman ◽  
R L Chappell
Keyword(s):  
Dynamic Equilibrium ◽  
Aminobutyric Acid ◽  
Significant Feature ◽  
Gamma Aminobutyric Acid ◽  
Synaptic Interaction ◽  
Wide Range ◽  
Order Neuron ◽  
Intracellular Response ◽  
Dim Light ◽  
Ocellar Nerve

The intracellular response of the ocellar nerve dendrite, the second order neuron in the retina of the dragonfly ocellus, has been modified by application of various drugs and a model developed to explain certain features of that response. Curare blocked the response completely. Both picrotoxin and bicuculline eliminated the "off" overshoot. Bicuculline also decreased the size of response and the sensitivity. gamma-Aminobutyric acid (GABA), however, increased the size of response. The evidence indicates the possibility that the receptor transmitter is acetylcholine and is inhibitory to the ocellar nerve dendrite whereas the feedback transmitter from the ocellar nerve dendrite may be GABA and is facilitory to receptor transmitter release. The model of synaptic feedback interaction developed to be consistent with these results has certain important features. It suggests that the feedback transmitter is released in the dark to increase input sensitivity from receptors in response to dim light. This implies that the dark potential of the ocellar nerve dendrite may be determined by a dynamic equilibrium established by synaptic interaction between it and the receptor terminals. Such a system is also well suited to signalling phasic information about changes in level of illumination over a wide range of intensities, a characteristic which appears to be a significant feature of the dragonfly median ocellar response.

scholarly journals Electrophysiology of the Insect Dorsal Ocellus

1961 ◽  
Vol 44 (3) ◽  
pp. 641-657 ◽  
Author(s):  
Philip Ruck
Keyword(s):  
Photoreceptor Cells ◽  
Nerve Fibers ◽  
Flicker Fusion Frequency ◽  
Generator Potential ◽  
Fusion Frequency ◽  
Nerve Impulses ◽  
Postsynaptic Potential ◽  
Potential Component ◽  
Flicker Fusion ◽  
Ocellar Nerve

The ERG of the dragonfly ocellus has been analyzed into four components, two of which originate in the photoreceptor cells, two in the ocellar nerve fibers (Ruck, 1961 a). Component 1 is a sensory generator potential, component 2 a response of the receptor axons. Component 3 is an inhibitory postsynaptic potential, component 4, a discharge of afferent nerve impulses in ocellar nerve fibers. Responses to flickering light are examined in terms of this analytic scheme. It has been found that the generator potential can respond to higher rates of flicker—up to 220/sec.—than can the receptor axon responses, the postsynaptic potential, or the ocellar nerve impulses. The maximum flicker fusion frequency as measured by fusion of the ERG is that of the sensory generator potential itself.

scholarly journals Neural Organization of the Median Ocellus of the Dragonfly

1972 ◽  
Vol 60 (2) ◽  
pp. 148-165 ◽  
Author(s):  
John E. Dowling ◽  
Richard L. Chappell
Keyword(s):  
Electron Microscopy ◽  
Synaptic Vesicles ◽  
Receptor Cell ◽  
Presynaptic Membrane ◽  
Cell Axon ◽  
Axon Terminals ◽  
Neural Organization ◽  
Dense Cluster ◽  
Median Ocellus ◽  
Ocellar Nerve

Two types of presumed synaptic contacts have been recognized by electron microscopy in the synaptic plexus of the median ocellus of the dragonfly. The first type is characterized by an electron-opaque, button-like organelle in the presynaptic cytoplasm, surrounded by a cluster of synaptic vesicles. Two postsynaptic elements are associated with these junctions, which we have termed button synapses. The second synaptic type is characterized by a dense cluster of synaptic vesicles adjacent to the presumed presynaptic membrane. One postsynaptic element is observed at these junctions. The overwhelming majority of synapses seen in the plexus are button synapses. They are found most commonly in the receptor cell axons where they synaptically contact ocellar nerve dendrites and adjacent receptor cell axons. Button synapses are also seen in the ocellar nerve dendrites where they appear to make synapses back onto receptor axon terminals as well as onto adjacent ocellar nerve dendrites. Reciprocal and serial synaptic arrangements between receptor cell axon terminals, and between receptor cell axon terminals and ocellar nerve dendrites are occasionally seen. It is suggested that the lateral and feedback synapses in the median ocellus of the dragonfly play a role in enhancing transients in the postsynaptic responses.

scholarly journals Electrophysiology of the Insect Dorsal Ocellus

1961 ◽  
Vol 44 (3) ◽  
pp. 629-639 ◽  
Author(s):  
Philip Ruck
Keyword(s):  
Spontaneous Activity ◽  
Nerve Fibers ◽  
Inhibitory Influence ◽  
Nerve Impulses ◽  
Receptor Cells ◽  
Inhibitory Postsynaptic Potentials ◽  
Rhythmic Discharge ◽  
Ocellar Nerve ◽  
Sustained Inhibition ◽  
Nerve Discharge

Large nerve fibers in the ocellar nerves of dragonflies are spontaneously active. In the absence of inhibitory influence the spontaneous activity is rhythmic. Inhibition occurs in the dark-adapted state and during illumination. Miniature inhibitory postsynaptic potentials occur in the dark-adapted state. These modulate by temporary suppression the otherwise rhythmic discharge of ocellar nerve impulses. The presence of random spontaneous receptor cell excitations is inferred from the presence of the miniature i.p.s.p.'s. Light stimulates many or all the receptor cells simultaneously, masking the random spontaneous activity of individual receptor cells. The result is a sustained hyperpolarizing i.p.s.p. and sustained inhibition of the nerve discharge. Preceding resumption of the spontaneous activity at "off" the i.p.s.p. may oscillate, overshoot the baseline as a negative after-potential, or do both. These phases of the off-effect may generate nerve impulses in an off-burst.

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