Patch-clamp analysis of voltage- and ligand-activated whole-cell currents in freshly dissociated neurons of the locust optic lobe

Whole-cell patch-clamp recordings were obtained from 116 freshly dissociated neuronal somata from the optic lobe of adult locusts (Schistocerca gregaria). Prerequisites were a papain treatment and the directed transfer of somata to the recording chamber by dabbing. Of the recorded somata, 65 were from lamina and 51 from other optic lobe neurons. All somata supported voltage-activated outward currents and some (24% of optic lobe, 3% of lamina neurons) also fast inward currents. Most lamina neurons supported an outward current that activated (V _1/2=−8.5 mV) and inactivated rapidly and a sustained outward current. Some lamina and most optic lobe neurons expressed only a sustained outward current (V _1/2=−9.4 mV). GABA and histamine elicited inward currents at negative holding potentials. Most optic lobe (95%) but only 18% of lamina neurons showed a γ-aminobutyric acid (GABA) current, whereas a similar percentage of optic lobe (50%) and lamina neurons (67%) expressed a histamine current. Both currents reversed near the chloride equilibrium potential, were reversibly reduced by picrotoxin, and did not show rundown. Thus, they likely represent chloride currents mediated by ionotropic receptors. Our data indicate that the lamina neurons recorded mainly represent monopolar cells postsynaptic to histaminergic photoreceptors. The optic lobe neurons, on which GABA and histamine apparently act as inhibitory neurotransmitters, are more heterogeneous. Accepted: 30 November 1997     

Hippocampal astrocytes exhibit Ca2+-elevating muscarinic cholinergic and histaminergic receptors in situ

Recent findings suggest that astrocytes respond to neuronally released neurotransmitters with Ca2+ elevations. These Ca2+ elevations may trigger astrocytes to release glutamate, affecting neuronal activity. Neuronal activity is also affected by modulatory neurotransmitters that stimulate G protein-coupled receptors. These neurotransmitters, including acetylcholine and histamine, might affect neuronal activity by triggering Ca2+-dependent release of neurotransmitters from astrocytes. However, there is no physiological evidence for histaminergic or cholinergic receptors on astrocytes in situ. We asked whether astrocytes have these receptors by imaging Ca2+-sensitive dyes sequestered by astrocytes in hippocampal slices. Our results show that immunocytochemically identified astrocytes respond to carbachol and histamine with increases in intracellular free Ca2+ concentration. The H1 histamine receptor antagonist chlorpheniramine inhibited responses to histamine. Similarly, atropine and the M1-selective muscarinic receptor antagonist pirenzepine inhibited carbachol-elicited responses. Astrocyte responses to histamine and carbachol were compared with responses elicited by alpha1-adrenergic and metabotropic glutamate receptor agonists. Individual astrocytes responded to different subsets of receptor agonists. Ca2+ oscillations were the prevalent response pattern only with metabotropic glutamate receptor stimulation. Finally, functional alpha1-adrenergic receptors and muscarinic receptors were not detected before postnatal day 8. Our data show that astrocytes have acetylcholine and histamine receptors coupled to Ca2+. Given that Ca2+ elevations in astrocytes trigger neurotransmitter release, it is possible that these astrocyte receptors modulate neuronal activity.     

Differential regulation of a homologous peptidergic neuron in grasshoppers: evolution of a neural circuit

The vasopressin-like immunoreactive (VPLI) neurons of grasshoppers have paired cell bodies in the suboesophageal ganglion and both anterior and posterior running axons. In non-oedipodine grasshopper species (e.g. Schistocerca gregaria), most of their arborisations are distributed in dorsal and lateral neuropil, while in oedipodine species (e.g. Locusta migratoria), the neurons have additional extensive axonal projections in both the optic lobes and proximal portions of the ganglionic peripheral nerves. This study demonstrates that these morphological differences correlate with their physiology. In L. migratoria, VPLI neuron activity is regulated primarily via a spontaneously active interneuron which descends from the brain. This descending interneuron is inhibited by a light-activated brain extraocular photoreceptor. Regulation of VPLI neuron activity by an extraocular photoreceptor is also seen in the other oedipodine grasshopper investigated. In the four non-oedipodines examined (from two subfamilies), we find no extraocular photoreceptor regulation of VPLI neuron activity. Despite this, VPLI neuron in S.␣gregaria does appear to be driven by a descending interneuron homologous to that in L. migratoria. The descending interneuron in both species receives similar mechanosensory input and excites the VPLI neuron via cholinergic synapses. Histamine injection into the medial protocerebrum of both species causes strong inhibition of the descending interneuron. The evolution of the neural circuitry, by which an extraocular photoreceptor comes to regulate the descending interneuron in oedipodine species, is discussed. Accepted: 6 January 1998     

Detection of object motion by a fly neuron during simulated flight

Object detection on the basis of relative motion was investigated in the fly at the neuronal level. A representative of the figure detection cells (FD-cells), the FD1b-cell, was characterized with respect to its responses to optic flow which simulated the presence of an object during translatory flight. The figure detection cells reside in the fly's third visual neuropil and are believed to play a central role in mediating object-directed turning behaviour. The dynamical response properties as well as the mean response amplitudes of the FD1b-cell depend on the temporal frequency of object motion and on the presence or absence of background motion. The responses of the FD1b-cell to object motion during simulated translatory flight were compared to behavioural responses of the fly as obtained with identical stimuli in a previous study. The behavioural responses could only partly be explained on the basis of the FD1b-cell's responses. Further processing between the third visual neuropil and the final motor output has to be assumed which involves (1) facilitation of the object-induced responses during translatory background motion at moderate temporal frequencies, and (2) inhibition of the object-induced turning responses during translatory background motion at high temporal frequencies. Accepted: 9 October 1999     

Functional consequences of mutations in the Drosophila histamine receptor HCLB

The gene hclB encodes a histamine-gated chloride channel subunit in Drosophila melanogaster. Mutations in hclB lead to defects in the visual system and altered sensitivity to the action of ivermectin. To investigate whether this member of the Cys-loop receptors is common across the Insecta, we analysed the genomes of seven other insect species (Diptera, Hymenoptera, Coleoptera) and revealed orthologues of hclB in all of them. Sequence comparisons showed high identity levels between the orthologues, indicating similar constraints and conserved function between the species. Two D. melanogaster mutants, hclB^T1 (P293S) and hclB^T2 (W111*, a null mutation) were tested for the lapse into, and recovery from, paralysis induced by high temperature or the anaesthetic action of halothane. At 41 °C, the hclB^T2 flies lapsed into coma faster than wild-type or the hclB^T1 flies, while both mutants recovered more slowly. A substantially impaired recovery rate was also observed in hclB^T1 after anaesthesia with halothane. Enhanced synaptic signalling at low-intensity light stimuli was registered on electroretinograms recorded from the two mutant strains. Our results suggest that HCLB may play an essential and conserved role in insect neurophysiology.     

Evidence for the possible existence of a second polarization-vision pathway in the locust brain

For spatial orientation and navigation, many insects derive compass information from the polarization pattern of the blue sky. The desert locust Schistocerca gregaria detects polarized light with a specialized dorsal rim area of its compound eye. In the locust brain, polarized-light signals are passed through the anterior optic tract and tubercle to the central complex which most likely serves as an internal sky compass. Here, we suggest that neurons of a second visual pathway, via the accessory medulla and posterior optic tubercle, also provide polarization information to the central complex. Intracellular recordings show that two types of neuron in this posterior pathway are sensitive to polarized light. One cell type connects the dorsal rim area of the medulla with the medulla and accessory medulla, and a second type connects the bilaterally paired posterior optic tubercles. Given the evidence for a role of the accessory medulla as the master clock controlling circadian changes in behavioral activity in flies and cockroaches, our data open the possibility that time-compensated polarized-light signals may reach the central complex via this pathway for time-compensated sky-compass navigation.     

Visual pigment processes and prolonged pupillary responses in insect photoreceptor cells

The visual pigment in the peripheral retinular cells of the hoverfly Syrphus balteatus was investigated by absorbance difference measurements. Different visual pigments were found in the dorsal versus the ventral part of the eye in the male, but not in the female. In the male in the dorsal part of the eye the visual pigment has an isosbestic point at 513 nm; in the ventral part this value is 490 nm. The latter value is found in the female in both parts of the eye.Prolonged pupillary responses were studied in the male Syrphus and appeared to be most marked in the ventral part of the eye. In both hoverfly and blowfly prolonged pupillary responses are induced by short wavelength light only; i.e., by light which excessively can convert rhodopsin into metarhodopsin. By contrast, in butterflies red light (and a long dark adaptation time) is necessary to evoke a prolonged pupillary response. It was demonstrated in both hoverfly and blowfly that long wavelength light, which reconverts metarhodopsin into rhodopsin, inhibits a prolonged pupillary response; or, accelerates pupil opening.Based on material presented at the European Neurosciences Meeting, Florence, September 1978     

Transneuronal uptake of horseradish peroxidase in the central nervous system of dipterous insects

Summary Horseradish peroxidase (HRP) applied to lesioned neurons in the retina and thoracic ganglia of the flies Musca, Calliphora and Drosophila labeled axon terminals, dendrites and perikarya of the severed neurons after anterograde or retrograde passage. In addition, HRP reaction product secondarily labeled intact neurons that are contiguous with injured nerve cells. In many cases labeling of optic lobe neurons remote from primarily filled ones was also seen (here called tertiary labeling). HRP labeling was extensive and both primarily and transneuronally filled neurons could be resolved in almost as much detail as Golgi-impregnated or cobalt-silver-labeled cells. Electron microscopy showed that in both primarily and secondarily filled neurons, reaction product was distributed diffusely in the cytoplasm.Transneuronal uptake of HRP was specific to certain types of neurons in the brain and thus displayed certain pathways. The pathways resolved by transneuronal labeling with HRP extend from the optic lobes to the thoracic ganglia and include visual neurons previously identified electrophysiologically and anatomically.Transneuronal HRP uptake, although believed to occur in vivo, could not be shown to be dependent on synaptic activity. Three other heme peptides tested were taken up by injured neurons, but showed no transneuronal labeling: lactoperoxidase, cytochrome c, and microperoxidase.     

肌肽在血管性痴呆治疗中的应用及研究进展

血管性痴呆是临床发病率排在第二位的认知障碍性疾病,以白质损伤引起的认知功能障碍和胶质细胞的激活为主要病理表现。目前临床上药物治疗疗效有限,且不能有效逆转损伤、减缓疾病的进程,因此,对新药物的研发存在迫切的需求。肌肽(β-丙氨酰-L-组氨酸)是由β-丙氨酸和L-组氨酸两种氨基酸组成的天然二肽,能够由外周进入神经中枢系统,转变成组氨酸后成为组胺,是体内组胺的天然储存库,对急性脑缺血损伤发挥保护作用。近年研究发现肌肽对血管性痴呆的保护作用不是通过肌肽-组氨酸-组胺的途径,而是通过抑制兴奋性氨基酸毒性、氧自由基的产生、胶质细胞的激活以及髓鞘的退化发挥保护作用,由此证明肌肽对于血管性痴呆有着潜在的临床治疗作用。本文针对肌肽对血管性痴呆治疗的研究进展进行综述。     

Haemocyte involvement in the repair of the insect central nervous system after selective glial disruption

Summary Injection of physiologically inert particles (fluorescent microspheres) has a profound effect on neural repair of central nervous connectives of the cockroach Periplaneta americana following selective glial disruption. The injected particles, which do not gain direct access to the central nervous tissues, are taken up by a relatively small proportion (< 10%) of the haemocytes. This interference with haemocyte function virtually abolishes the appearance of the granule-containing cells (which are prominently involved in normal glial repair) and produces abnormal reorganization of the superficial glial elements. These results are interpreted as evidence that the granule-containing cells are derived from haemocytes which are critically involved in glial repair.     

Putative circadian pacemaker cells in the antenna of the hawkmoth Manduca sexta

Antennal sensory neurons in the fruit fly Drosophila melanogaster express circadian rhythms in the clock gene PERIOD (PER) and appear to be sufficient and necessary for circadian rhythms in olfactory responses. Given recent evidence for daily rhythms of pheromone responses in the antenna of the hawkmoth Manduca sexta, we examined whether a peripheral PER-based circadian clock might be present in this species. Several different cell types in the moth antenna were recognized by monoclonal antibodies against Manduca sexta PER. In addition to PER-like staining of pheromone-sensitive olfactory receptor neurons and supporting cells, immunoreactivity was detected in beaded branches contacting the pheromone-sensitive sensilla. The nuclei of apparently all sensory receptor neurons, of sensilla supporting cells, of epithelial cells, and of antennal nerve glial cells were PER-immunoreactive. Expression of per mRNA in antennae was confirmed by the polymerase chain reaction, which showed stronger expression at Zeitgeber-time 15 compared with Zeitgeber-time 3. This evidence for the expression of per gene products suggests that the antenna of the hawkmoth contains endogenous circadian clocks.     

Adaptation and responses to changes in illumination by second- and third-order neurones of locust ocelli

Intracellular recordings have been made of responses to step, ramp and sinusoidal changes of light by second-order L-neurones and a third-order neurone, DNI, of locust (Locusta migratoria) ocelli.

The spatial resolutions of the apposition compound eye and its neuro-sensory feature detectors: observation versus theory

For 100 years three ideas dominated efforts to understand the apposition compound eye. In Müller's theory, the eye viewed the panorama through an array of little windows without overlaps and without gaps, with no details within windows. Spatial resolution then depended on the interommatidial angle (Deltaphi) and the number of ommatidia. In the second proposal, the insect detected the temporal modulation of the light, which was limited by the aperture of the lens and the wavelength, assuming good focus. Modulation is the change of intensity in the receptor, usually caused by motion of a spatial contrast in the stimulus. Thirdly, motion was detected from the successive temporal modulations at adjacent visual axes. Recently, two more principles arose. The light-sensitive elements, called rhabdomeres, project through the nodal point of the lens to the outside world, and the resolution was limited by their grain size, like the pixels in a digital camera. Finally, detection of contrast and colour was limited by the signal/noise ratio (SNR) which was improved by brighter light and more visual pigment. These five physical principles provide satisfying explanations of eye function but they all originated from theory. Actual measurements of resolution depend on the operation of the test. The visual system of the honeybee recognizes a limited variety of simple cues, but there is no evidence that the pattern of ommatidial stimulation is re-assembled, or even seen. The known cues are: the temporal modulation of groups of receptors, the direction and angular velocity of motion, some measure of the spatial disruption of the pattern or the length of edge (related to spatial frequency and contrast), colour, the intensity, the position of the centre and the size of large well-separated areas of black or colour, the angle of orientation of a bar or grating, radial or tangential edges, and bilateral symmetry. Neurons connected to more than two adjacent ommatidia collaborate in the detection of cues, and the resolution depends on the neuro-sensory feature detectors at work at the time. Although some behavioural and electrophysiological measurements give a spatial resolution similar to the interommatidial angle, different spatial properties of neuro-sensory detectors predominate at different light intensities and with a diurnal rhythm. During the long history of this topic, the belief that the resolution ought to be Deltaphi has frequently been overturned by experimental measurement.     

The effects of an anti-mitotic drug,bleomycin, on glial repair in an insect central nervous system

Summary The DNA-binding drug, bleomycin, has a profound effect on neural repair following selective glial disruption by ethidium bromide. The contribution of the granule-containing cells (which normally appear in the early stages of repair) is greatly reduced, the restoration of the blood-brain barrier is delayed and the ultrastructural organization of the reorganising perineurium is dramatically changed. The aberrant perineurial structure and function observed in the presence of bleomycin are postulated to result from the effects of the drug on haemocytes which, together with endogenous reactive cells, contribute to the normal process of glial repair.     

Cell recruitment during glial repair: the role of exogenous cells

Summary Selective disruption of the neuroglia in penultimate abdominal connectives of the cockroach nerve is followed by a rapid accumulation of cells in the perineurial layer of the lesion. Subsequently, there is an abrupt, secondary, rise in cell numbers in the undamaged perineurial tissues, anterior to the lesion and adjacent to the 4th abdominal ganglia. By 7 days the increased cell numbers are again effectively confined to the original lesion zone. The initial rise in cell numbers is postulated to result from an invasion by blood-borne haemocytes and the subsequent increase, in undamaged perineurial tissues, from the mobilization of endogenous reactive cells. Recruitment of the endogenous cells is inhibited if the haemocytes are excluded from the lesion. There is a slower mobilization of sub-perineurial cells, which, again, is inhibited following exclusion of haemocytes from the lesion zone. It is postulated that the recruitment of the endogenous reactive cells is initiated by the invading haemocytes which transform to granule-containing cells and release diffusible morphogenic and/or mitogenic factors.     

Directional control by male gypsy moths of upwind flight along a pheromone plume in three wind speeds

By attaching a reflective strip to the thorax, we documented with video recordings in a wind tunnel the spatial orientation of male gypsy moths, Lymantria dispar, as they flew along a plume of sex pheromone. In wind speeds of 61, 122, and 183 cm s⁻¹, moths flew very similar tracks along a pheromone plume. Moths aimed their thrust closer to upwind in increasing wind speeds using a roll maneuver. As a result, the orientation of their visual flow field, represented by the slip angle (the angular distance between the direction of flight and the longitudinal body axis), remained relatively constant. We propose that directional control during self-steered zigzagging is achieved by rolling, thereby maintaining a set slip angle. Following a roll at the apex of a turn that aligns the moth with its preferred slip angle, a moth banks toward a cross wind leg. By banking moths may maintain a stable image flow at oblique angles to their longitudinal body axis. Accepted: 16 July 1998     

Evolution of color vision in pierid butterflies: blue opsin duplication,ommatidial heterogeneity and eye regionalization in <Emphasis Type="Italic">Colias erate</Emphasis>

This paper documents the molecular organization of the eye of the Eastern Pale Clouded Yellow butterfly, Colias erate (Pieridae). We cloned four cDNAs encoding visual pigment opsins, corresponding to one ultraviolet, two blue and one long wavelength-absorbing visual pigments. Duplication of the blue visual pigment class occurs also in another pierid species, Pieris rapae, suggesting that blue duplication is a general feature in the family Pieridae. We localized the opsin mRNAs in the Colias retina by in situ hybridization. Among the nine photoreceptor cells in an ommatidium, R1-9, we found that R3-8 expressed the long wavelength class mRNA in all ommatidia. R1 and R2 expressed mRNAs of the short wavelength opsins in three fixed combinations, corresponding to three types of ommatidia. While the duplicated blue opsins in Pieris are separately expressed in two subsets of R1-2 photoreceptors, one blue sensitive and another violet sensitive, those of Colias appear to be always coexpressed.