Activities evoked in different strain structures by stimulation of the contralateral tectum in the chick]

In the chick, as soon as hatching, the responses recorded in various areas in the "accessorius hyperstriatum" (Wulst) seem to be very localized in relation with the stimulated region of the contralateral tectum. Very similar results are obtained within the other striate structures. These observations suggest in first part, that the tectal efferents project very diffusely to various striate structures and, in other part, that it exists in these a rather precise tectotopy and a columnar organisation. These results appear very constant during the first month of the hatching.     

Relative Wulst volume is correlated with orbit orientation and binocular visual field in birds

In mammals, species with more frontally oriented orbits have broader binocular visual fields and relatively larger visual regions in the brain. Here, we test whether a similar pattern of correlated evolution is present in birds. Using both conventional statistics and modern comparative methods, we tested whether the relative size of the Wulst and optic tectum (TeO) were significantly correlated with orbit orientation, binocular visual field width and eye size in birds using a large, multi-species data set. In addition, we tested whether relative Wulst and TeO volumes were correlated with axial length of the eye. The relative size of the Wulst was significantly correlated with orbit orientation and the width of the binocular field such that species with more frontal orbits and broader binocular fields have relatively large Wulst volumes. Relative TeO volume, however, was not significant correlated with either variable. In addition, both relative Wulst and TeO volume were weakly correlated with relative axial length of the eye, but these were not corroborated by independent contrasts. Overall, our results indicate that relative Wulst volume reflects orbit orientation and possibly binocular visual field, but not eye size.     

嗅球僧帽细胞具有编码气味空间信息的能力

刺激源的方位是刺激的重要特性之一.行为学的研究发现,动物能够利用气味到达左右鼻腔的时间差和强度差信息对气味方位进行感知,但作为嗅觉系统第一神经中枢的嗅球,是否具有利用两侧鼻间差信息对气味方位进行编码的能力一直受到质疑.为探讨该问题,在本研究中通过比较嗅球中84个僧帽细胞对同侧气味刺激、对侧气味刺激以及对侧气味刺激略先于同侧气味刺激时的反应,发现有29个僧帽细胞可被同侧气味所兴奋,其中18个虽然对对侧气味刺激不反应,但对侧气味的存在却能显著降低其对同侧气味刺激的反应.另外,50个僧帽细胞在只给予同侧或对侧气味刺激时不反应,但其中11个在对侧刺激略先于同侧刺激的方式给出气味时,表现出明显的兴奋性反应.我们的研究结果一方面提示僧帽细胞具有编码气味到达两个鼻腔的时间差,或气味源位置信息的能力;另一方面也表明对侧刺激不仅能对同侧嗅球僧帽细胞产生抑制效应,还可能存在目前还不明确的机制而产生兴奋效应.     

Somatotopic representation of climbing fiber projections from limb cutaneous afferents to the paramedian lobule of the cat cerebellum

Climbing fiber projections to the cerebellar paramedian lobule were investigated electrophysiologically by stimulation of bilateral superficial radial nerve (SR) and superficial peroneal nerve (SP) in the cat anesthetized with pentobarbitone. In the medial zone of the paramedian lobule, short latency climbing fiber responses to stimulation of the ipsilateral SR were recorded rostrally from the top caudal part of the intermediate folia and short latency responses to stimulation of the ipsilateral SP were obtained caudally from the bottom caudal part of the folia. In the central zone, long latency responses to stimulation of the bilateral SR and SP were obtained. "Four limbs area" in which these responses were recorded was 1.0-1.2 mm in width. Short latency responses to stimulation of the ipsilateral SR were observed rostrally from this area, and short and long latency responses to stimulation of the ipsilateral SP were distributed caudally from this area. In the lateral zone, short and long latency responses to stimulation of the ipsilateral SR were recorded rostrally from the rostral part of the intermediate folia, and long latency responses to stimulation of the ipsilateral SP were observed caudally from the caudal part of the folia. In the most lateral zone, short and long latency responses to stimulation of the ipsilateral SR were obtained rostrally from the rostral part of the intermediate folia, and long latency responses to stimulation of ipsilateral SP were recorded only in the bottom caudal part of the folia caudally from the caudal part of the folia.     

Anatomy,neurophysiology and functional aspects of the nucleus isthmi in salamanders of the family Plethodontidae

Summary Tongue-projecting plethodontid salamanders have massive direct ipsilateral retinal afferents to the tectum opticum as well as a large and well developed nucleus isthmi. Retrograde staining revealed two subnuclei: A ventral one projecting to the contralateral tectal hemisphere and a dorsal one projecting back to the ipsilateral side. The isthmic nuclei show a retinotopic organization, which is in register with that of the tectum. Electrophysiological recordings from nucleus-isthmi neurons revealed response properties that are very similar to those found in tectal neurons. Thus, there is no substantial processing of tectal neural activity in the nucleus isthmi. Measurements of peak latencies after electrical and light stimulation suggest the continuous coexistence of 4 representations of the visual field in the tectum mediated by (1) the contralateral and (2) the ipsilateral direct retinal afferents, (3) the uncrossed and (4) the crossed isthmo-tectal projection. (1) and (2) originate at the same moment in the retina and arrive simultaneously in the tectum. It is assumed that in plethodontid salamanders with massive ipsilateral retino-tectal projections depth perception based on disparity cues is achieved by comparison of these images.Representations mediated by (3) and (4) arriving in the tectum at the same time as (1) and (2) originate 10–30 ms earlier in the retina. It is hypothesized that these time differences between (1)/(2) and (3)/(4) are used to calculate three-dimensional trajectories of fast-moving prey objects.Abbreviations EL edge length - FDA fluoresceine dextranamine - RDA tetramethylrhodamine dextranamine - RF receptive field     

A comparison of problem solving by extrapolation before and after removal of the archicortex and Wulst in cows]

The change in the capacity for extrapolation was studied in crows after ablation of Wulst and the archicortex. After the ablation of the archicortex, the solution of the extrapolation problem does not change. After the ablation of Wulst, the number of "refusals" to solve increases, the number of correct responses diminishes, although it remains significantly higher than the number of errors. It is assumed that the archicortex and Wulst play no decisive part in the process of solving problems involving extrapolation; yet Wulst apparently controls the achievement of the final reaction, by-passing the screen.     

Sound localisation in crickets

Intracellular recordings were made in the brain of the cricket Gryllus bimaculatus from an ascending auditory interneuron (AN1). Acoustic stimuli with calling song temporal pattern were delivered via earphones in a preparation with the acoustic trachea cut (attenuation of crossing sound > 30 dB). The input-output function of this cell was then determined by recording its responses to stimulation of the ipsilateral ear alone, of the contralateral ear alone and to stimulation of both ears simultaneously with the same or different carrier frequencies and intensities.This interneuron was excited by the ear ipsilateral to its axon and dendritic field and unresponsive to stimuli presented to the axon-contralateral ear alone. However, in binaural stimulation experiments, the response to a constant ipsilateral stimulus was progressively reduced as the intensity of a simultaneous contralateral stimulus was increased, above a threshold intensity.Tuning curves for threshold of this inhibition, determined in binaural stimulation experiments, indicated significant inhibition in the range 3–20 kHz with lowest threshold at 4–5 kHz. The inhibition was unaffected by sectioning of the contralateral circumoesophageal or neck connective, indicating that the inhibitory influence crosses the midline at the level of the prothoracic ganglion. Intracellular recordings from AN1 in the prothoracic ganglion confirmed that it was indeed neurally inhibited by inputs from the contralateral ear.Tuning curves for excitation of an omega neuron (ON1) by the ear ipsilateral to its soma and also the tuning of inhibition of ON1 by its contralateral ON1 partner, closely match the tuning of inhibition of AN1 and to a lesser extent, of AN2. This was taken as evidence that each AN1 is inhibited by the contralateral ON1. The significance of this interaction for directional hearing and phonotaxis is discussed.Abbreviations AP/CHP action potentials per chirp - AN1, AN2 ascending auditory interneurons 1, 2 - ON1 omega neuron 1 - ipsi ipsilateral contra contralateral - PTG prothoracic ganglion loc lateral ocellar nerve - On optic nerve an antennal nerve - coc circum-oesophageal connective so sound off     

Reparative neurogenesis in the brain and changes in the optic nerve of adult trout <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> after mechanical damage of the eye

Reparative proliferation and neurogenesis in the brain integrative centers after mechanical eye injury in an adult trout Oncorhynchus mykiss have been studied. We have found that proliferation and neurogenesis in proliferative brain regions, the cerebellum, and the optic tectum were significantly enhanced after the eye injury. The cerebellum showed a significant increase in the proliferative activity of the cells of the dorsal proliferative zone and parenchymal cells of the molecular and granular layers. One week after the injury, PCNA-positive radial glia cells have been identified in the tectum. We have found for the first time that the eye trauma resulted in the development of local clusters of undifferentiated cells forming so called neurogenic niches in the tectum and cerebellum. The differentiation of neuronal cells detected by labeling cells with antibodies against the protein HuC/D occurred in the proliferative zones of the telencephalon, the optic tectum, cerebellum, and medulla of a trout within 2 days after the injury. We have shown that the HuC/D expression is higher in the proliferative brain regions than in the definitive neurons of a trout. In addition, we have examined cell proliferation, migration, and apoptosis caused by the eye injury in the contra- and ipsilateral optic nerves and adjacent muscle fibers 2 days after the trauma. The qualitative and quantitative assessment of proliferation and apoptosis in the cells of the optic nerve of a trout has been made using antibodies against PCNA and the TUNEL method.     

3H]-GABA selective retrograde labeling of neurons in the pigeon thalamo-Wulst pathway

Evidence is presented which is consistent with a specific retrograde labeling of GABAergic neurons following [3H]-GABA application in their zone of termination. [3H]-GABA injection in the pigeon Wulst leads to perikaryal retrograde labeling in the ipsilateral thalamic visual relay, n. dorsolateralis anterior thalami, pars lateralis (DLLv). This result gives further support to the biochemical evidence of the existence, in the pigeon, of a GABAergic projection from DLLv to the ipsilateral visual Wulst.     

Xenopus exhibits seasonal variation in retinotectal latency but not tecto-isthmo-tectal latency

1. The tectum of Xenopus receives visuotopic input from both eyes. The contralateral eye's projection reaches the tectum directly, via the optic nerve. The ipsilateral eye's projection reaches the tectum indirectly, via the nucleus isthmi and isthmo-tectal projection. 2. Because of the multi-synaptic nature of the ipsilateral pathway, there is an inherent delay between the time that information from the contralateral eye reaches the tectum and the time that information from the ipsilateral eye arrives at the tectum. The length of the intertectal delay is a function of the latencies of the contralateral and ipsilateral pathways. 3. The length of this intertectal delay has functional, as well as developmental, implications with regard to the role of N-methyl-D-aspartate receptors in tectal cell activity and development of orderly synaptic connections. 4. We have found that the latencies of the contralateral and ipsilateral pathways exhibit a seasonal variation, increasing during the winter months. The increases of both latencies during the winter were of similar magnitude, indicating that there were no significant changes in intertectal delay. The seasonal alteration in contralateral latency was not affected by dark-rearing and was affected to only a minor extent by a week-long alteration of ambient temperature.     

Vibrissal inputs into the motor cortex of adult and developing rats

Field potentials (FP) and responses of single neurones to electrical stimulation of vibrissal pads have been recorded in motor cortex in the albino mature and developing rats. The FPs were characterized by 3-phasic shape and high stability in mature rats. The FPs evoked by contralateral stimuli have a range of onset latency of 4 to 24 ms (peak of distribution 8-11 ms); those to ipsilateral stimuli have a latency of 4 to 23 ms (peak of distribution 12-16 ms). Responses of single neurones were evoked with a latency of 9 to 20 ms. Usually, the FPs were evoked by both contralateral and ipsilateral stimulation, and in some tracks were effective only ipsilateral stimuli in the developing rats beginning from the 11th day of life. The FPs in such animals were less stable and more fatigable. During 2-4 weeks of life, FPs evoked by contralateral stimulation appeared with a latency of 15 to 46 ms; during the same period, a latency of single unit responses ranged between 20 to 33 ms. The FPs to ipsilateral stimuli appeared with a latency of 18 to 47 ms, a latency of single unit responses of 27 to 47 ms. The results indicate functional immaturity of vibrissal system up to the end of the first month of rat life.     

Binocular responses of neurons in the barn owl's visual Wulst

Binocular responses have been recorded extra-cellularly at 58 sites in the barn owl's (Tyto alba) visual Wulst. Neurons showed disparity tuning to stimulation with moving bars, moving sinewave gratings and a moving visual-noise stimulus. Responses to sinewave gratings as a function of disparity were cyclic, with the period of a cycle of the response being correlated to one cycle of the stimulus. Cyclic responses were also found when bars or noise were used as a stimulus, but, especially in response to visual noise, one response peak, the main peak, was different from the other peaks, the sidepeaks: usually, the main peak was either higher or narrower or both higher and narrower than the sidepeaks. When the responses to different spatial frequencies were compared, response maxima coincided at the main peak, but not at the other peaks. In analogy to auditory physiology the disparity at which the frequency-independent peak occurs is termed characteristic disparity. Spatial-frequency tuning revealed broad tuning, ranging from 1 to more than 3 octaves at 50% of the maximal response. Disparity tuning was broad at the onset of the response and sharpened later. The data are discussed within the framework of a model for the neural representation of visual disparity that was derived from a model proposed earlier for the representation of interaural time difference, the main cue for encoding sound-source azimuths in the barn owl.Abbreviations ITD interaural time difference - CD characteristic delay - RF receptive field     

Electrophysiological analysis of cortico-tectal connections in the turtle

Two types of evoked potentials are recorded in the tectum mesencephali in response to electrical stimulation of the forebrain surface of the turtleEmys orbicularis. The results of a layer-by-layer analysis show that evoked potentials of type I in response to stimulation of the hippocampal and piriform cortex are generated outside the tectum. Evoked potentials of type II, consisting of two surface-negative components, are recorded in the tectum in response to stimulation of the rostro-central surface of the forebrain. The first component appeared after a latent period of 20 msec and lasted 40–60 msec; the second component appeared after 80–100 msec and lasted 100–300 msec. Layer-by-layer and pharmacological analysis showed that the first component of the type II evoked potential is generated in the tegmental structures of the mesencephalon, whereas the second (long-latency) is generated in the tectum. The tectal origin of the second component is confirmed by its interaction with the tectal response to photic stimulation or to electrical stimulation of the optic nerve, evidence that these evoked potentials are generated by common structures. The efferent pathway from the dorsal cortex to the primary visual center is unilateral and has features of polysynaptic projections (long latent period, low lability).     

The role of visual experience in the formation of binocular projections in frogs

Many parts of the visual system contain topographic maps of the visual field. In such structures, the binocular portion of the visual field is generally represented by overlapping, matching projections relayed from the two eyes. One of the developmental factors which helps to bring the maps from the two eyes into register is visual input. The role of visual input is especially dramatic in the frog, Xenopus laevis. In tadpoles of this species, the eyes initially face laterally and have essentially no binocular overlap. At metamorphosis, the eyes begin to move rostrodorsally; eventually, their visual fields have a 170 degree region of binocular overlap. Despite this major change in binocular overlap, the maps from the ipsilateral and contralateral eyes to the optic tectum normally remain in register throughout development. This coordination of the two projections is disrupted by visual deprivation. In dark-reared Xenopus, the contralateral projection is nearly normal but the ipsilateral map is highly disorganized. The impact of visual input on the ipsilateral map also is shown by the effect of early rotation of one eye. Examination of the tectal lobe contralateral to the rotated eye reveals that both the contralateral and the ipsilateral maps to that tectum are rotated, even though the ipsilateral map originates from the normal eye. Thus, the ipsilateral map has changed orientation to remain in register with the contralateral map. Similarly, the two maps on the other tectal lobe are in register; in this case, both projections are normally oriented even though the ipsilateral map is from the rotated eye. The discovery that the ipsilateral eye's map reaches the tectum indirectly, via a relay in the nucleus isthmi, has made it possible to study the anatomical changes underlying visually dependent plasticity. Retrograde and anterograde tracing with horseradish peroxidase have shown that eye rotation causes isthmotectal axons to follow abnormal trajectories. An axon's route first goes toward the tectal site where it normally would arborize but then changes direction to reach a new tectal site. Such rearrangements bring the isthmotectal axons into proximity with retinotectal axons which have the same receptive fields. Anterograde horseradish peroxidase filling has also been used to study the trajectories and arborizations of developing isthmotectal axons. The results show that the axons enter the tectum before the onset of eye migration but do not begin to branch profusely until eye movement begins to create a zone of binocular space.(ABSTRACT TRUNCATED AT 400 WORDS)     

Stabilization of motor asymmetry in the goldfish under the influence of optokinetic stimulation

Adaptation as a memory model appears, at the cellular level, as an increase in the resistivity of neurons to fatigue under the influence of repetitive natural training stimulation. Selective induction of adaptational changes in separate compartments of one and the same neuron can also serve as an important instrument for identification of the roles of these compartments in the integrative function of the individual neuron. Mauthner neurons (MNs) of fishes (the goldfish in particular) possess a clearly differentiated soma and two dendrites, lateral and ventral ones. The soma and lateral dendrite of each MN receive afferentation from the ipsilateral vestibular apparatus; at present, the functional and morphological aspects of selective adaptational modifications induced in these compartments by adequate vestibular stimulation have been examined in detail. As to the ventral MN dendrite receiving visual afferentation from the contralateral eye via the ipsilateral tectum, it remained impossible until now to realize the respective approach. We found that training sessions of visual optokinetic stimulation performed in certain modes provide selective activation of one MN through its ventral dendrite and increase the resistivity of this cell to fatiguing stimulation. Therefore, we first demonstrated the possibility of adaptational changes in an individual ventral dendrite of the MN. If fishes were preliminarily adapted with respect to vestibular stimulation, and the resistivity of the soma and lateral dendrite was selectively increased, the resistivity to fatiguing visual test stimulation also increased. On the other hand, if fishes were preliminarily adapted with respect to visual stimulation, the resistivity to fatiguing vestibular stimulation also increased. The observed increase in the resistivity of MNs of fishes adapted due to sensory stimulation of one afferent input with respect to sensory stimulation of other sensory input, as well as an increase in the resistivity to sensory stimulation of one modality, probably show that the mechanism of increase in the resistivity is the same in both cases. Neirofiziologiya/Neurophysiology, Vol. 40, No. 3, pp. 211–220, May–June, 2008.     

Ipsilateral retinal projections into the tectum during regeneration of the optic nerve in the cichlid fish Haplochromis burtoni: a Dil study in fixed tissue.

Retinal projections were experimentally manipulated in a bony fish to reveal conditions under which considerably enlarged ipsilateral projections developed and persisted. Three experimental groups were studied: animals after unilateral enucleation, after unilateral nerve crush, and after enucleation and crush of the remaining optic nerve. At 29 days after unilateral enucleation alone, no enhanced ipsilateral projection had developed. After nerve crush, however, large numbers of retinal fibers regenerated into the ipsilateral tectum. Retrogradely filled, ipsilaterally projecting ganglion cells were distributed throughout the entire retina. After 15 days regenerating retinal fibers covered the entire ipsilateral tectum. At later stages the ipsilateral projection showed progressive reduction in coverage of the tectum. Combining enucleation with nerve crush led to an ipsilateral projection that covered the tectum at 28 days and later. In this experimental situation the development of an ipsilateral projection appears to be a two-step process: (1) Fibers are rerouted to the ipsilateral side at the diencephalon, and (2) ipsilateral fibers persist in the tectum only in the absence of a contralateral projection while they appear to be eliminated in the other cases.     

The antidromic activation of tectal neurons by electrical stimuli applied to the caudal medulla oblongata in the toad,Bufo bufo L.

In order to specify the tectal projection to the bulbar/spinal regions, the antidromic responses of the physiologically identified tectal neurons as well as the gross antidromic field responses in the optic tectum to electrical stimuli applied to the caudal medulla were examined in the paralyzed common toad, Bufo bufo. The antidromic field potential was recorded in the optic tectum in response to electrical stimuli applied to the ventral paramedian portion of the contralateral caudal medulla (where the crossed tecto-spinal pathway of Rubinson (1968) and Lázár (1969) runs), but generally not when they were applied to various parts of the ipsilateral caudal medulla. The antidromic field potential was largest at the superficial part of Layer 6 or at the border between Layers 6 and 7 of the optic tectum, indicating that neurons in these layers project to the contralateral caudal medulla. Mapping experiments of the antidromic field potential over the optic tectum showed that the antidromic field potential was recorded mainly in the lateral part of it, indicating that this part of the optic tectum is the main source of projection neurons to the contralateral caudal medulla. Various classes of tectal neurons as well as retinal ganglion neurons were identified from the characteristics of the response properties to moving visual stimuli and the properties of the receptive fields. Of these, the Class T1, T2, T3, T4, T5(1), T5(2), T5(3), and T5(4) tectal neurons were activated antidromically by stimuli applied to the contralateral caudal medulla. Only a limited proportion of the Class T5(1) neurons was activated antidromically by stimuli applied to the ipsilateral caudal medulla. On the other hand, the Class T7 and T8 neurons, as well as the Class R2, R3, and R4 retinal neurons, were not activated antidromically by stimuli applied to the caudal medulla of either side. These results suggest a possibility that these tectal neurons which project to the medullary regions form the substrate of the sensorimotor interfacing and contribute to the initiation or coordination of the visually guided behavior, such as prey-catching.     

Early positive component of the tectal evoked potential ofSqualus acanthias during electrical stimulation of the optical nerve

The evoked potential of the tectum opticum during electrical stimulation of the optic nerve was studied in acute experiments on the dogfishSqualus acanthias L. The negative phase of the "classical" negative-positive evoked potential of the contralateral hemisphere of the tectum opticum was shown to be a complex potential, including an early positive component. A similar potential also was recorded from the ipsilateral hemisphere. Enhancement of this positive potential on insertion of the recording electrode deep into the brain, its resistance to functional block on application of potassium chloride to the brain surface, and recording a similar potential from the surface of the floor of the third ventricle after extirpation of the tectum opticum are evidence of the nontectal location of the source of this evoked potential component. On the basis of existence of a focus of maximal activity in the rostral zones of the brain beneath the tectum opticum, and disappearance of the early positive component during functional block and extirpation of this brain region, it is concluded that a leading role in the generation of this component is played by thalamic nuclei.M. V. Lomonosov Moscow State University. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 61–67, January–February, 1984.     

Antinociceptive effects of lacosamide on spinal neuronal and behavioural measures of pain in a rat model of osteoarthritis

Introduction

Alterations in voltage-gated sodium channel (VGSC) function have been linked to chronic pain and are good targets for analgesics. Lacosamide (LCM) is a novel anticonvulsant that enhances the slow inactivation state of VGSCs. This conformational state can be induced by repeated neuronal firing and/or under conditions of sustained membrane depolarisation, as is expected for hyperexcitable neurones in pathological conditions such as epilepsy and neuropathy, and probably osteoarthritis (OA). In this study, therefore, we examined the antinociceptive effect of LCM on spinal neuronal and behavioural measures of pain, in vivo, in a rat OA model.

Methods

OA was induced in Sprague Dawley rats by intraarticular injection of 2 mg of monosodium iodoacetate (MIA). Sham rats received saline injections. Behavioural responses to mechanical and cooling stimulation of the ipsilateral hind paw and hindlimb weight-bearing were recorded. In vivo electrophysiology experiments were performed in anaesthetised MIA or sham rats, and we recorded the effects of spinal or systemic administration of LCM on the evoked responses of dorsal horn neurones to electrical, mechanical (brush, von Frey, 2 to 60 g) and heat (40°C to 50°C) stimulation of the peripheral receptive field. The effect of systemic LCM on nociceptive behaviours was assessed.

Results

Behavioural hypersensitivity ipsilateral to knee injury was seen as a reduced paw withdrawal threshold to mechanical stimulation, an increase in paw withdrawal frequency to cooling stimulation and hind limb weight-bearing asymmetry in MIA-treated rats only. Spinal and systemic administration of LCM produced significant reductions of the electrical Aβ- and C-fibre evoked neuronal responses and the mechanical and thermal evoked neuronal responses in the MIA group only. Systemic administration of LCM significantly reversed the behavioural hypersensitive responses to mechanical and cooling stimulation of the ipsilateral hind paw, but hind limb weight-bearing asymmetry was not corrected.

Conclusions

Our in vivo electrophysiological results show that the inhibitory effects of LCM were MIA-dependent. This suggests that, if used in OA patients, LCM may allow physiological transmission but suppress secondary hyperalgesia and allodynia. The inhibitory effect on spinal neuronal firing aligned with analgesic efficacy on nociceptive behaviours and suggests that LCM may still prove worthwhile for OA pain treatment and merits further clinical investigation.     

Ipsilateral retinal projections into the tectum during regeneration of the optic nerve in the cichlid fish Haplochromis burtoni: A dil study in fixed tissue

Retinal projections were experimentally manipulated in a bony fish to reveal conditions under which considerably enlarged ipsilateral projections developed and persisted. Three experimental groups were studied: animals after unilateral enucleation, after unilateral nerve crush, and after enucleation and crush of the remaining optic nerve. At 29 days after unilateral enucleation alone, no enhanced ipsilateral projection had developed. After nerve crush, however, large numbers of retinal fibers regenerated into the ipsilateral tectum. Retrogradely filled, ipsilaterally projecting ganglion cells were distributed throughout the entire retina. After 15 days regenerating retinal fibers covered the entire ipsilateral tectum. At later stages the ipsilateral projection showed progressive reduction in coverage of the tectum. Combining enucleation with nerve crush led to an ipsilateral projection that covered the tectum at 28 days and later. In this experimental situation the development of an ipsilateral projection appears to be a two-step process: (1) Fibers are rerouted to the ipsilateral side at the diencephalon, and (2) ipsilateral fibers persist in the tectum only in the absence of a contralateral projection while they appear to be eliminated in the other cases. © 1992 John Wiley & Sons, Inc.