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The goals of this study were to describe the morphology, neurotransmitter content and synaptic connections of neurons in primate retinas that contain the neuropeptide secretoneurin. Amacrine cells were labeled with antibodies to secretoneurin in macaque and baboon retinas. Their processes formed three distinct plexuses in the inner plexiform layer: one in the outermost stratum, one in the center and one in the innermost stratum. In light microscopic double immunolabeling experiments, GABA was colocalized with secretoneurin in these cells, but glycine transporter 1 and Substance P were not. ON bipolar cell axon terminals labeled with antibody to the cholecystokinin precursor, G6-gly, have ON responses to stimulation of short wavelength sensitive (S) cones. Axons of these bipolar cells made contacts with amacrine cell dendrites containing secretoneurin. Secretoneurin-IR amacrine cells also made contacts with retinal ganglion cell dendrites labeled with antibody to the photopigment melanopsin, which have OFF responses to stimulation of S cones. Using electron microscopic immunolabeling, 436 synapses from macaque retina were analyzed. Axons from bipolar cells were identified by their characteristic synaptic ribbons; their synaptic densities were asymmetric like those of excitatory synapses in the brain. Amacrine cells made and received conventional synapses with symmetric synaptic densities, like those of inhibitory synapses in the brain. Ganglion cell dendrites were identified by their absence of presynaptic specializations; they received inputs from both amacrine cells and bipolar cells. The majority of inputs to the secretoneurin-IR amacrine cells were from other amacrine cells, but they also received 21% of their input from bipolar cells. They directed most of their output, 54%, to amacrine cells, but there were many synapses onto bipolar cell axons and ganglion cell dendrites, as well. The synaptic connections were very similar in the three plexuses with one notable exception; output synapses to bipolar cells were significantly less common in the innermost one, where the S-ON bipolar cells terminate. Taken together, these findings suggest that the secretoneurin-IR amacrine cells in primates receive excitatory input from S-ON bipolar cells and, in turn, inhibit intrinsically photosensitive retinal ganglion cells.

Gamma knife surgery (GKS) is used for the treatment of various human brain disorders. However, the biological effects of gamma ray irradiation on both the target area, and the surrounding tissues are not well studied. The effects of gamma ray exposure to both targeted and untargeted regions were therefore evaluated by monitoring gene expression changes in the unilateral irradiated (60 Gy) and contralateral un-irradiated striata in the rat. Striata of irradiated and control brains were dissected 16 hours post-irradiation for analysis using a whole genome 44K DNA oligo microarray approach. The results revealed 230 induced and 144 repressed genes in the irradiated striatum and 432 induced and 239 repressed genes in the un-irradiated striatum. Out of these altered genes 39 of the induced and 16 of the reduced genes were common to both irradiated and un-irradiated tissue. Results of semiquantitative, confirmatory RT-PCR and western blot analyses suggested that gamma-irradiation caused cellular damage, including oxidative stress, in the striata of both hemispheres of the brains of treated animals.

Object. Although reports in the literature indicate that thalamic pain syndrome can be controlled with chemical hypophysectomy, this procedure is associated with transient diabetes insipidus. It was considered reasonable to attempt gamma knife surgery (GKS) to the pituitary gland to control thalamic pain. Methods. Inclusion criteria in this study were poststroke thalamic pain, failure of all other treatments, intolerance to general anesthetic, and the main complaint of pain and not numbness. Seventeen patients met these criteria and were treated with GKS to the pituitary. The target was the pituitary gland together with the border between the pituitary stalk and the gland. The maximum dose was 140 to 180 Gy. All patients were followed for more than 3 months. Conclusions. An initial significant pain reduction was observed in 13 (76.5%) of 17 patients. Some patients experienced pain reduction within 48 hours of treatment. Persistent pain relief for more than 1 year was observed in five (38.5%) of 13 patients. Rapid recurrence of pain in fewer than 3 months was observed in four (30.8%) of 13 patients. The only complication was transient diabetes insipidus in one patient. It would seem that GKS of the pituitary might have a role to play in thalamic pain arising after a stroke.

The short wavelength-sensitive (blue) cone bipolar cells was found to have a nonrandom distribution by analyzing the nearest neighbors and by calculating the density recovery profile (DRP). Blue cones had been shown previously to have a nonrandom distribution (Curcio et al., 1991). The relationship between the two arrays was then analyzed by calculating the cross-correlational density recovery profile (cDRP), which indicates the local density of blue cones around each blue cone bipolar cell. Although both cell types appeared to be distributed uniformly at the macroscopic level, the cDRP was 1.7 times higher within 15 μm of each bipolar cell perikaryon than in the surrounding area. The area of higher density was approximately the same as that in which the blue cone bipolar cells made synaptic contacts with blue cones. The finding that the blue cones and the blue cone bipolar cells were closer together than expected suggests that the positions of the perikarya of these neurons were influenced by their synaptic connections or other developmental interactions.

A distinct subpopulation of bipolar cells in macaque monkey retina was labeled with antisera that recognize glycine-extended cholecystokinin precursors. The labeled bipolar cells were found throughout the retina and had dendrites contacting a subpopulation of cone pedicles and axons ramifying in the fifth stratum of the inner plexiform layer. Several lines of evidence indicate that the labeled bipolar cells are a single type despite some variations in their morphology. First, the density of perikarya and their diameters varied continuously as a function of eccentricity. Second, the positions of perikarya within the inner nuclear layer and the level at which the axons branched in the inner plexiform layer were constant at all eccentricities. Bipolar cells with similar morphology have been described previously as “blue cone bipolar cells” (Mariani, 1984b), but there was no direct evidence that this was the case. In this study, we show by light microscopy that labeled bipolar cells have dendrites ending exclusively upon presumptive blue cones labeled by Procion black dye. All blue cones were contacted by labeled bipolar cells, and virtually all bipolar cells contacted blue cones, the only exceptions being in regions where blue cones had been lost. Approximately 20% more labeled bipolar cells than blue cones were found at every eccentricity; thus, connections between blue cones and labeled bipolar cells were not strictly one to one. The mean number of cones presynaptic to each bipolar cell was 1.2, and the mean number of bipolar cells postsynaptic to each cone was 1.8. By an electron microscopic study of labeled bipolar cell dendrites, we determined that they became central elements of ribbon synapses in blue cones. Some of their ribbon synapses were unusual: in one type, a single, large labeled dendrite was postsynaptic to two or more ribbons, while in the other type, ribbons had two or more central elements. The presence of these invaginating contacts and the axonal terminals in the proximal inner plexiform layer suggest that the labeled bipolar cells depolarize to short-wavelength stimuli and function to relay information from blue cones to the inner plexiform layer. There were also other, unlabeled bipolar cell dendrites that received inputs from blue cones at basal junctions and triad-associated flat contacts, which suggests that there are additional types of bipolar cells conveying information from short- wavelength cones in the primate retina.

Diagnostic modalities that can distinguish brain tumors from eloquent cortices or nerve fiber bundles are important for neurosurgery. For identifying nerve fiber bundles, various techniques such as diffusion tensor imaging and subcortical stimulation mapping have been used. In this article, we propose localization of nerve fiber bundles by polarization-sensitive optical coherence tomography (PS-OCT) for the first time. PS-OCT performs tomographic imaging by measuring the travel distance and the change in polarization of the backscattered light from the tissue at different traverse positions, enabling selective visualization of birefringent tissues such as nerve fiber bundles. We examined the imaging of nerve fiber bundles in blocks of fixed rat brains. Nerve fiber bundles in internal and external capsules of the rat brains appearing on the surfaces of the coronal, horizontal, and sagittal planes were identified as to their locations and orientations. The nerve fiber bundles were clearly visualized by PS-OCT. The image penetration depth of the PS-OCT images was about 1.0 mm in gray matter and about 0.5 mm in white matter, so the refractive indices of gray and white matters were assumed to be 1.4.

Background/Aims: Manipulation of brain functions via Gamma Knife (GK) irradiation would have numerous applications in clinical and experimental neurology. Methods: Alteration of brain functions in the unilaterally irradiated striatum was indexed through monitoring freely moving rat behaviors. Spontaneous activity and rotations on the apomorphine test, which can detect dopaminergic function imbalance, were indexed employing our behavior tracking system. The spatial distribution of necrotic lesions was explored using serial sections, and was assumed to represent the real foci of the GK target. Results: Distinct behavioral alterations corresponded to the precise locations of the lesions in various areas of the basal ganglia. Displacement of the irradiation sites in the anteromedial direction increased spontaneous activity, and posterolateral shift provoked circling behavior on the apomorphine test. Conclusion: Accurate positioning of the target is crucial for experimental GK irradiation locally focused on domains of a small brain such as that of the rat. Here, we propose a protocol for converting the ‘intended’ focus, based on brain map coordinates, to a ‘planned’ focus on the MR imaging coordinate system with the Régis-Valliccioni stereotactic frame.

Object. An animal model has been developed to study the effect of gamma knife surgery(GKS) on cerebral function. Methods. A rat was fixed in a newly developed Régis—Valliccioni frame that enables the target region to be planned directly on the magnetic resonance images. The left striatum was irradiated with 150 Gy via a 4-mm collimator of the Leksell gamma knife. Apomorphine (dopamine agonist) was administered to elicit a circling behavior (apomorphine test) after the GKS so as to examine the time course of the changes in dopaminergic functions of irradiated striatum. After a series of behavioral analyses, irradiated brains were subjected to histological examination. Necrosis was observed in the irradiated area surrounded by hemorrhage and gliosis. The distance between the histologically estimated and planned centers of the irradiation areas was 1.0 ± 0.5 mm. The extent of the distance was due to errors along dorsoventral axis. The distribution of the irradiation areas influenced the activity and the circling behaviors in apomorphine test, which was suggestive of involvement of the nigrostriatal pathway. Conclusions. Targeting by using the Régis—Valliccioni frame was very accurate compared with targeting with coordinates based on brain maps used hitherto. Although targeting improved the accuracy, further effort will still be necessary to reduce errors along dorsoventral axis. The apomorphine test indicated a reduced dopaminergic function of the irradiated area including striatum, which accompanied histological changes after a high dose of irradiation (150 Gy).

Rationale: Two or three decades ago, cancer pain was treated by surgical/chemical hypophysectomy. In one report, the control of central pain (thalamic pain syndrome) was also approached with chemical hypophysectomy. Although in most of the patients these treatments resulted in a decrease in severe pain, concomitantly severe adverse effects (panhypopituitarism, diabetes insipidus and visual dysfunction) occurred in most patients. This historical evidence prompted us to perform Gamma Knife surgery (GKS) for this kind of intractable severe pain using a high irradiation dose to the pituitary stalk/gland. In the majority of patients, marked pain relief was achieved, surprisingly without any of the complications mentioned above. Materials and Methods: A prospective multicenter study was conducted to evaluate the efficacy and safety in patients treated in Prague, Hong Kong and Tokyo. Indications of this treatment were: (1) failure of other effective treatment approaches prior to GKS, (2) good general patient condition (Karnofsky performance status >40%), (3) response to morphine for pain control (cancer pain), and (4) no previous radiotherapy of brain metastases (GKS/conventional radiotherapy). Eight patients with severe cancer pain due to bone metastasis and 12 patients with post-stroke thalamic pain syndrome were treated with GKS. The target was the border between the pituitary stalk and gland. Maximum dose was 160 Gy for cancer pain and 140 Gy for central pain. Follow-up included 6 patients (>1 month) with cancer pain and 8 patients (> 6 months) with thalamic pain syndrome. Results: All patients (6/6) with cancer pain experienced significant pain reduction, and 87.5% (7/8) of the patients with thalamic pain had initially significant pain reduction. In some patients, pain reduction was delayed for several hours. Pain relief was noted within 7 days (median 2 days). No recurrence was observed in the patients with cancer pain. However, in 71.4% (5/7) of the patients with thalamic pain syndrome, disease recurred during the 6-month follow-up. Up to now, other complications have not been observed. Conclusion: Our clinical study protocol is only preliminary. Further clinical results on the management of thalamic pain are required to develop this treatment protocol. However, efficacy and safety have been shown in all our cases. In our opinion, this treatment has a potential to control severe pain, and GKS will play an important role in the management of intractable pain.

In primates, the retinal ganglion cells that project to the magnocellular layers of the lateral geniculate nucleus have distinctive responses to light, and one of these has been identified morphologically as the parasol ganglion cell. To investigate their synaptic connections, we injected parasol cells with Neurobiotin in lightly fixed baboon retinas. The five ON-center cells we analyzed by electron microscopy received approximately 20% of their input from bipolar cells. The major synaptic input to parasol cells was from amacrine cells via conventional synapses and, in this respect, they resembled alpha ganglion cells of the cat retina. We also found the gap junctions between amacrine cells and parasol ganglion cells that had been predicted from tracer-coupling experiments. To identify the presynaptic amacrine cells, ON-center parasol cells were injected with Neurobiotin and Lucifer yellow in living macaque retinas, which were then fixed and labeled by immunofluorescence. Two kinds of amacrine cells were filled with Neurobiotin via gap junctions: a large, polyaxonal cell containing cholecystokinin and a smaller one without cholecystokinin. There were also appositions between cholecystokinin-containing amacrine cell processes and parasol cell dendrites. Cholinergic amacrine cell processes often followed parasol cell dendrites and made extensive contacts. In other mammals, the light responses of polyaxonal amacrine cells like these and cholinergic amacrine cells have been recorded, and the effects of acetylcholine and cholecystokinin on ganglion cells are known. Using this information, we developed a model of parasol cells that accounts for some properties of their light responses.

Antisera which recognize glycine-extended precursors of the peptide chole-cystokin in labeled neurons in the macaque retina with dendrites that ran obliquely and had diffuse dendritic terminals as is the case for blue cone bipolar cells described previously. They clearly formed a single population since the density and sizes of their perikarya varied monotonically with eccentricity, while the levels of their perikarya and axon terminals were constant. Short-wavelength cones were also labeled in some preparations, either with Procion Black or anti-blue opsin, and the labeled bipolar cells received input exclusively from these cones. The dendrites formed the central elements at ribbon synapses in the short-wavelength cones, and the axons of the labeled bipolar cells branched in the fifth stratum of the inner plexiform layer. Taken together, these findings indicate that the labeled bipolar cells were different from the invaginating midget bipolar cells that contact middle- and long-wavelength cones and suggest that the labeled bipolar cells depolarize in response to increments in short-wavelength stimuli. There were numerous, unlabeled bipolar cell dendrites receiving inputs from short-wavelength cones at other types of contacts, however, and these presumably belonged to bipolar cells with hyperpolarizing light responses.

The synaptic contacts between photoreceptors and horizontal cells in the retina of the turtle (Geoclemys) were studied. Horizontal cells were classified into three types according to their intracellularly recorded spectral responses: luminosity, biphasic chromaticity, and triphasic chromaticity horizontal cells (LHC, BHC, and THC). These cells were then iontophoretically filled with horseradish peroxidase (HRP). The various types of photoreceptors located within the dendritic field of the HRP-filled horizontal cells were identified either as rods or as one of the three chromatic types of cones; the latter were identified by the presence and colors of their oil droplets in the inner segments. The synaptic contacts between photoreceptors and labeled horizontal cells were then investigated by light and electron microscopy of serial sections on three LHCs, two BHCs, and one THC. LHCs made synaptic contacts with about 100 photoreceptors, including rods and three chromatic types of cones; two-thirds of these photoreceptors contacted the cell body and the remaining its axon terminal. BHCs contacted about 30 cones; red-, green-, and blue-sensitive cones in the ratio of 3:4:1. THC contacted 20 cones; red- and blue-sensitive cones in the ratio of 2:1. The dendritic processes of HRP-filled horizontal cells were found as the lateral element of the ribbon synaptic complexes. The present finding suggests that the responses of BHC and THC to red flashes are fed directly from red-sensitive cones in addition to the feedback pathway of cone-horizontal cell connections in the previous studies.

Using combined physiological and anatomical methods, we have shown that triphasic chromaticity horizontal cells (THC) in the turtle retina make ribbon synaptic contacts with about 20 cones, two-thirds were red-sensitive, while the rest were blue-sensitive. The response of THC to red flashes appeared to be generated via synapses from red-sensitive cones; this interpretation differs from those of the previous studies where only blue-sensitive cones were thought to make synaptic contacts with the THC.

L-type horizontal cells (271) of the carp retina were studied with the aid of intracellular injections of Lucifer yellow and horseradish peroxidase (HRP). Coupling among these cells was revealed by passage of the dye out of the injected cell. Thick processes that crossed axons filled with Lucifer yellow also contained the stain. These thick processes appear to be the axon terminals of other horizontal cells. Serial reconstruction of an axon terminal by electron microscopy revealed two groups of elements connected to the axon terminal with putative gap junctions. One large-diameter group was identified as axon terminals of other cells. From the results of the Lucifer dye-coupling experiments, the smaller-diameter elements are thought to be the axons of other horizontal cells. Thus, the axon terminals of carp horizontal cells have putative gap-junctional contacts not only with other axon terminals but also with the axons of other horizontal cells. This newly discovered connection could serve as a pathway for signal transfer between the cell body and the axon terminal of different horizontal cells.

In this study we examine the fine structure of mechanosensory hairs in the antennule of crayfish. The sensory hair is a stiff shaft with feather-like filaments. The hair's base is a large expansion of membrane which allows the hair shaft to deflect. The sensory transducing elements are located far from the hair, but are coupled mechanically with the hair shaft by a fine extracellular chorda. The sensory element is a type of scolopidium which consists of a scolopale cell and three sensory cells with a 9 + 0 type ciliary process. This type of scolopidium is characteristic of the chordotonal organ that has no cuticular structure on the surface of the exoskeleton. In this crustacean hair receptor, the deflection on the cuticular hair is transmitted through the chorda to the scolopidium which is a tension-sensitive transducer. The present study reveals that the mechanosensory hair of decapod crustaceans is a chordotonal organ accompanied by a cuticular hair structure. We also discuss comparative aspects of cuticular and subcuticular chordotonal organs in arthropods.