bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptation to suppression of visual information during catching
Authors: Lacquaniti F , Maioli C
Published: March 2018

We address the problem of whether and how adaptation to suppression of visual information occurs in catching behavior. To this end, subjects were provided with advance information about the height of fall and the mass of a ball and an auditory cue signaled the time of release. Adaptation did occur, as indicated by the unimpaired ability to catch the ball without vision; however, it involved a major reorganization of the muscle responses. The subjects were unable to produce anticipatory activity consistently, but preset the responses elicited by the impact. These responses were more complex and prolonged than those observed in the control experiments (with vision). In particular, medium- and long- latency responses were much larger, and the changes in elbow, wrist, and metacarpophalangeal angles following impact were more oscillatory than in the control. The general pattern of the EMG responses switched from that characteristic of catching with vision to that characteristic of catching without vision from the first trial of each experiment. However, the responses produced without vision were calibrated adaptively in the course of an experiment. In fact, the limb oscillations induced by the impact were significantly larger in the first trial than in the following trials. This seems to suggest that the parameters of the responses are adjusted based on an internal model of the dynamic interaction between the falling ball and the limb. This model is initially constructed from a priori knowledge on impact parameters and is subsequently updated on the basis of the kinesthetic and cutaneous information obtained during the first trial.
A quantitative study of the coexistence of peptides in varicosities within the superficial laminae of the dorsal horn of the rat spinal cord
Authors: Tuchscherer MM , Seybold VS
Published: March 2018

While several peptides have been shown to coexist in perikarya within dorsal root ganglia of rat, coexistence of peptides has not been confirmed in axons associated with these neurons. In this study, the coexistence of substance P (SP) with somatostatin (SOM), calcitonin gene-related peptide (CGRP), dynorphin A 1–8 (DYN), neurotensin (NT), galanin (GAL), and 5-HT in varicosities was visualized using fluorescence immunohistochemistry. Densities of immunoreactive varicosities within laminae I and II of the dorsal horn of the rat spinal cord were quantified by computer-assisted image analysis. Decreases in densities of immunoreactive varicosities as a result of multiple unilateral dorsal rhizotomies were used to determine proportions of immunoreactive varicosities associated with primary afferent neurons. Three observations were made. (1) Dorsal rhizotomy depleted greater than one-third of the varicosities individually immunoreactive for SP, SOM, GAL, or DYN, confirming the association of these peptides with primary afferent neurons. (2) SP coexisted with CGRP, GAL, and DYN in varicosities within the dorsal horn of normal animals. (3) CGRP-, SP+CGRP-, and SP+GAL-immunoreactive varicosities were nearly depleted following dorsal rhizotomy. The depletion of these peptides, particularly in combination, indicates that they may be used as markers for varicosities of some primary afferent neurons within the superficial laminae of the dorsal horn of the rat spinal cord.
Bursting induces persistent all-or-none EPSPs by an NMDA-dependent process in piriform cortex
Authors: Hoffman WH , Haberly LB
Published: March 2018

Burst responses to stimulation of excitatory fiber tracts in olfactory cortex slices after removal of extracellular Mg2+ or decreases in extracellular Cl-, resulted in long-lasting changes in response properties of neurons following a return to normal bathing medium. After bursting activity, the response of pyramidal cells to stimulation of afferent or associational fiber systems consisted of the normal graded depolarizing postsynaptic potential and a new, high-amplitude depolarizing potential that followed the graded potential at a variable latency. The new late potential had a waveform that resembled the initial graded response, but it occurred in an all-or-none fashion with a discrete threshold and persisted for many hours. Threshold for the late potential was similar for different cells in the same slice and was not affected by intracellular current injection, indicating that a synchronized interaction among a large number of cells is involved in its generation. Properties of the late potential indicate that it is an EPSP. NMDA receptor antagonists (APV and ketamine) had little effect on the late potential but prevented its development if present during bursting activity. The possible relevance of these findings to the study of the neuronal substrate for long-term memory and epilepsy is discussed.
Responses of lateral geniculate neurons that survive long-term visual cortex damage in kittens and adult cats
Authors: Tumosa N , McCall MA , Guido W , Spear PD
Published: March 2018

Damage to visual cortex (areas 17–19) in kittens or adult cats produces severe retrograde degeneration of neurons in the dorsal lateral geniculate nucleus (LGN). However, some neurons survive in otherwise degenerated portions of the LGN after a visual cortex lesion at any age. Previous studies have shown that there are well-defined differences in potential retinal inputs, soma size, synaptic connections, outputs, and physiological properties of output targets of the surviving LGN cells in cats that received visual cortex damage at different ages. The present experiment investigated the relationships between these differences and the responses of surviving LGN neurons to visual stimulation. Recordings were made from surviving neurons in the degenerated A- and C-layers of the LGN in cats that had received a visual cortex lesion on the day of birth, at 8 weeks of age, or as adults (survival was 11.5–36 months). Normal adult cats were studied for comparison. The visual receptive field was mapped, and tests were carried out to classify each cell as X, Y, or W. In addition, quantitative methods were used to assess response amplitude, strength of receptive-field surround inhibition, spatial-frequency tuning to drifting or counterphased sine-wave gratings, and response to nondominant-eye stimulation for each cell. We found that surviving cells in all LGN layers respond to light, have normal receptive-field organization, and have normal eye dominance following a lesion at any age tested. In addition, gross retinotopic organization of the LGN is normal. However, 2 main abnormalities were observed following a lesion at all 3 ages. First, there is a reduction in the percentage of X cells in the A layers, from 62% in normal LGNs to about 15% in degenerated LGNs. Second, many surviving cells in both the A- and C-layers have abnormally large receptive-field centers. Other differences that were observed between normal A-layer cells and surviving A-layer cells could be attributed to the loss of X cells. These results indicate that cells within a structure that shows severe retrograde degeneration after brain damage can maintain relatively normal function and can take part in potentially important residual neural pathways. Previous studies indicate that these residual pathways can show both anatomical and physiological compensation for the brain damage, and the present findings bear on the consequences and mechanisms of this compensation.
Immunocytological localization of pedal peptide in the central nervous system and periphery of Aplysia
Authors: Pearson WL , Lloyd PE
Published: March 2018

Immunocytology using antisera raised to conjugated pedal peptide (Pep) was used to localize the peptide in the CNS and periphery of Aplysia. A total of over 200 neurons in the CNS exhibited Pep-like immunoreactivity. As expected from results presented in the previous paper, immunoreactive neurons were heavily concentrated in the pedal ganglia, primarily in a broad ribbon comprised of about 60 large contiguous neurons on the dorsal side of each ganglion. Smaller and less numerous immunoreactive neurons were found in the other ganglia. A number of neurons primarily located in the abdominal ganglia had dense networks of immunoreactive varicose fibers surrounding their cell bodies. Many immunoreactive axons were observed in peripheral nerves, particularly those nerves leaving the pedal ganglia. Analyses of sections of body wall indicated that Pep-like immunoreactivity was localized to a series of varicose axons that appeared to be associated with vascular spaces, muscle fibers, and other large cells. These axons likely arise from pedal ganglion nerves that were shown to transport large amounts of 35S-labeled Pep to the periphery. These results suggest that Pep is a transmitter-like neuropeptide that is likely to have a number of important physiological actions in Aplysia.
Visual receptive fields in the striate-recipient zone of the lateral posterior-pulvinar complex
Authors: Chalupa LM , Abramson BP
Published: March 2018

The lateral posterior (LP)-pulvinar complex of the cat is known to contain multiple visual areas. In the present study, we examined the receptive field properties of single neurons isolated in the lateral division of this complex (the LPI). The LPI is designated the striate- recipient zone because it is the only region of the LP-pulvinar receiving cortical projections from areas 17 and 18. The recordings revealed that the striate-recipient zone of LP comprises 2 subareas, which we have termed LPI-1 and LPI-2. In the main segment (LPI-1), virtually all cells responded securely to visual stimuli. The vast majority of these neurons were binocular, with relatively small and well-defined receptive fields. More than half of the cells were found to be directionally selective, and almost this many were orientation specific. The orientation tuning of these cells was found to be quite precise, comparable to complex cells in area 17. In contrast, in the small dorsolateral segment of the striate-recipient zone (the LPI-2), a substantial proportion of cells could not be visually activated. Here, the visual cells had very large receptive fields, and relatively few were direction or orientation selective. The LPI-2 receives subcortical inputs from the superficial layers of the superior colliculus, the hypothalamus, and cerebellum, while the LPI-1 is innervated only by cortical axons. It is suggested that the subcortical connections of the LPI-2 account for the differences in the response properties of the 2 striate-recipient areas. The present results, in conjunction with our previous findings on the principal tectorecipient zone (Chalupa et al., 1983), permit 2 generalizations regarding the functional organization of the cat's LP-pulvinar complex. First, there are clear differences among the visual areas of the LP-pulvinar in the cellular processing of visual information. Second, these functional differences can be related to the principal sources of visual input to the various divisions of the LP-pulvinar.
Dynamics of alpha-tubulin deacetylation in intact neurons
Authors: Black MM , Baas PW , Humphries S
Published: March 2018

The majority of the alpha-tubulin in cultured neurons is acetylated (Black and Keyser, 1987). The present studies examine the relationships of the acetylation and deacetylation reactions to tubulin assembly and disassembly in intact neurons. Extraction assays which separate assembled and unassembled tubulin pools reveal that greater than or equal to 99% of the total acetylated, as well as newly acetylated, tubulin is cytoskeletal associated. Treatment of neurons with depolymerizing drugs results in a progressive decrease in the levels of total tubulin in polymer and a corresponding increase in the levels of soluble tubulin. These drugs also cause a progressive decrease in the levels of acetylated alpha-tubulin in polymer that closely parallels in rate and extent that of total alpha-tubulin. However, there is no corresponding increase in soluble acetylated tubulin. Because the total levels of alpha-tubulin remain unchanged during drug treatment, the decrease in levels of acetylated alpha-tubulin during depolymerization must reflect its rapid conversion to nonacetylated alpha-tubulin. These findings suggest alpha-tubulin is acetylated in the polymeric form and that deacetylation is closely coupled to depolymerization. The close coupling between alpha-tubulin deacetylation and depolymerization provided a means of estimating the rate at which subunits cycle off microtubules in intact neurons. Acetate turnover on tubulin in intact neurons was determined both by pulse-chase protocols with 3H-acetate and by measuring the loss of acetylated subunits (using quantitative immunoblotting) under conditions of net microtubule depolymerization induced by colchicine. Both methods yielded similar results. Acetate turnover occurred biphasically; 30–50% of the acetate on tubulin turns over with a t1/2 of 1.5–2 hr, and the remaining half or more turns over with a t1/2 of 5–10 hr. We suggest that these kinetically distinguishable pools of acetylated alpha-tubulin reflect distinct pools of acetylated microtubules that differ in their average rates of subunit turnover.
Passive membrane properties of motorneurons and their role in long- distance signaling in the nematode Ascaris
Authors: Davis RE , Stretton AO
Published: March 2018

In the motornervous system of the large parasitic nematode, Ascaris suum, the dorsal and ventral nerve cords are connected by a repeating pattern of single identified motorneuron processes, called commissures (Stretton et al., 1978). By making microelectrode penetrations of the commissures, we here report the first successful intracellular recordings of nematode neurons. These cells, like muscle cells of Ascaris, exhibit resting potentials of approximately -30 to -40 mV. Several tests indicate that these are the normal resting potentials of the cells and are not low due to damage. Using 2 intracellular microelectrodes (one for stimulation and one for recording), we have determined the input resistance and cable properties of commissural motorneurons. Over the physiological voltage range, the steady-state I- V plots are linear with little indication that voltage-sensitive conductances are contributing substantially to signaling. The membrane capacitance is comparable to that of single biological membranes (range, 0.4–0.9 microF/cm2) and the internal resistivity (range, 79–314 omega cm) is similar to that found in other cells. Because of unusually large membrane resistances (range, 61–251 k omega cm2), the space constants, lambda, are high (range, 4–10 mm). Such membrane properties produce cells that are well-designed for conducting passive signals over long distances. This long-distance signaling ability appears to be due to the intrinsic properties of the motorneuron membrane itself.
Transport of cytoskeletal elements from parent axons into regenerating daughter axons
Authors: McQuarrie IG , Lasek RJ
Published: March 2018

The kinetics of slow axonal transport in newly regenerating axonal sprouts were compared with those in nonelongating axons. The slowly transported cytoskeletal proteins of ventral motor axons were prelabeled by microinjection of 35S-methionine into the spinal cord. Pulse-labeled slow transport “waves” were observed as they progressed from the surviving “parent” axon stumps (located proximal to a crush lesion) into regenerating “daughter” axon sprouts (located distal to the lesion). Prelabeled cytoskeletal elements of the parent axons were transported into daughter axons, to become distributed into 2 transport waves, “a” and “b.” The rate and composition of these waves corresponded to the slow transport subcomponents, SCa and SCb. The shapes of the “a” and “b” waves suggested that the cytoskeletal elements had been reorganized at the junction between the parent and daughter axons. This hypothesis was supported by quantitative analyses of the transport distribution for individual radiolabeled cytoskeletal proteins (actin, spectrin, a 58–67 kDa group that includes microtubule- associated proteins, calmodulin, and tubulin). Specifically, during the first week of outgrowth, the amounts of radiolabeled calmodulin and 58– 67 kDa proteins were greater in daughter axons than in nonregenerating control axons. These results support Paul Weiss's “conservative” model of axonal regeneration, which holds that the preexisting transported cytoskeletal elements that continually maintain axonal structure can also provide the cytoskeletal elements required for axonal regeneration. In addition, the results elucidate some of the reorganizational changes in cytoskeletal elements that occur when these are recruited from the parent axon to form daughter axons.
Monoclonal antibodies differentiate neurofilament and glial filament proteins in the goldfish visual pathway: probes for monitoring neurite outgrowth from retinal explants
Authors: Jones PS , Tesser P , Borchert J , Schechter N
Published: March 2018

The expression of the neurofilament proteins of the goldfish visual pathway reflects the degeneration and regeneration of the optic nerve after nerve crush. To monitor these processes, monoclonal antibodies (mAb) were generated to the intermediate filament proteins of this pathway. The predominant goldfish visual pathway intermediate filament proteins have a molecular weight of 58K and can be separated into 4 isoelectric variants, 2 of which are neuronal (ON1 and ON2) and 2 of which are non-neuronal (ON3 and ON4). The specificities of the mAbs were characterized biochemically and histologically. Immunoblot analysis demonstrated that 2 of the antibodies reacted specifically with the neurofilament proteins (ON1/ON2) and another antibody reacted specifically with the glial filament proteins (ON3/ON4) and with a 48K optic nerve protein of non-neuronal origin. Chymotrypsin digestion of the ON proteins and immunoblotting of the resulting fragments showed that the anti-ON1/ON2 mAbs were directed toward the variable domains of the filament proteins. In contrast, the anti-ON3/ON4 mAb was directed toward the 40K chymotrypsin-resistant region of the glial filament proteins containing the conserved intermediate filament core. When sections of optic nerve tissue were incubated with anti-ON1/ON2 or anti- ON3/ON4 mAbs, the staining resulted in either axonal or glial patterns, respectively. In retina, after optic nerve crush, anti-ON1/ON2 labeled retinal ganglion cells and Muller fibers. In contrast, prior to optic nerve crush, only Muller fibers were labeled. One of the neuronal- directed mAbs was used to decorate growing neurites from retinal explants; anti-ON1/ON2 reactivity appeared in a time-dependent manner that paralleled the expression of ON1/ON2 in vivo. Thus, the antibodies can differentiate these 2 types of goldfish intermediate filament proteins and can be used to monitor optic nerve regeneration in the goldfish visual pathway both in vivo and in vitro.
Association of neurotensin binding sites with sensory and visceromotor components of the vagus nerve
Authors: Kessler JP , Beaudet A
Published: March 2018

Specific neurotensin (NT) binding sites were recently shown to be highly concentrated in the nucleus of the solitary tract (NTS), which receives primary vagal afferents, and in the dorsal motor nucleus of the vagus (DMN), which contains the cell bodies of origin of vagal preganglionic neurons. To investigate the relationship of these binding sites with sensory and visceromotor components of the vagus nerve, they were labeled here in vitro, using monoiodo[Tyr3]neurotensin (125I-NT) and visualized by light microscopic radioautography in the dorsomedial medulla of both intact and unilaterally vagotomized rats, in the nodose ganglia of intact animals, and in ligated vagus nerves. Unilateral vagotomy performed above the nodose ganglion resulted in a significant ipsilateral decrease in 125I-NT binding within both the NTS and the DMN, suggesting that NT binding sites were associated with both primary afferent fibers and preganglionic nerve cell bodies. The selective radioautographic labeling of a subpopulation (approximately 15%) of neuronal perikarya in the nodose ganglion confirmed that a proportion of vagal afferent neurons contained NT binding sites. Following vagus nerve ligation, a pile up of radiolabeled NT binding sites was observed on both sides of the nerve crush, indicating that NT receptor components were transported both anterogradely and retrogradely along fibers of the vagus nerve. We conclude that NT receptors are synthesized and transported within a subpopulation of afferent and efferent components of the vagus nerve and that NT may therefore act presynaptically upon vagal axon terminals in both central and peripheral nervous systems.
Protein kinase inhibitors selectively block phorbol ester- or forskolin- induced changes in excitability of Aplysia neurons
Authors: Conn PJ , Strong JA , Azhderian EM , Nairn AC , Greengard P , Kaczmarek LK
Published: March 2018

Exposure of the bag cell neurons of Aplysia to activators of protein kinase C, such as phorbol esters, enhances electrically evoked action potentials by increasing the voltage-dependent calcium current. We have hypothesized that this effect is mediated by the activation of protein kinase C (PKC). An important prediction of this hypothesis is that inhibitors of PKC should inhibit these phorbol ester-induced changes in bag cell neuronal excitability. We have now found that treatment of bag cell neurons with the protein kinase inhibitor 1-[5- isoquinolinesulfonyl]-2-methyl piperazine (H-7) inhibits the phorbol ester-induced enhancement of bag cell action potentials and prevents the enhancement of calcium current by phorbol esters. The height and width of electrically evoked action potentials in bag cell neurons can also be enhanced by cAMP analogs or agents that elevate cAMP. These agents do not influence the major voltage-dependent calcium current in the bag cell neurons but may act by modulating potassium currents and other voltage-dependent currents. We have found that microinjection of a protein inhibitor of cAMP-PK (PKA-I) into isolated bag cell neurons prevents and reverses the effect of the adenylate cyclase activator forskolin on action potentials of these cells. In contrast, H-7 does not inhibit the effects of forskolin on a variety of responses in these cells, including its effects on action potentials, granule movement, and 32P incorporation into phosphoproteins. This suggests that H-7 is selective for PKC relative to cAMP-PK in intact bag cell neurons.
Peripheral target choice by homologous neurons during embryogenesis of the medicinal leech. II. Innervation of ectopic reproductive tissue by nonreproductive Retzius cells
Authors: Loer CM , Kristan WB
Published: March 2018

Most Retzius (Rz) cells innervate the body wall of their own and adjacent segments, whereas Rz cells in segments 5 and 6 [Rz (5,6)] innervate the reproductive tissue, which is found only in those segments. Results from the preceding paper (Loer and Kristan, 1989a) showed that Rz (5,6) and standard Rz cells do not normally compete for their respective peripheral targets. These experiments did not, however, distinguish between 2 other possible mechanisms of target selection: intrinsic differences in target preference or differences in the timing of target contact. In order to separate these possibilities experimentally, we transplanted reproductive primordia to standard segments. We found that standard Rz cells were capable of densely innervating ectopic reproductive tissue, provided the target was transplanted at an appropriate time and location. Furthermore, after some processes of standard Rz cells contacted ectopic reproductive tissue, the rest of the cell's processes showed their growth in a way reminiscent of Rz (5,6) processes. These results strongly suggest that Rz (5,6) innervate reproductive tissue at least partly because their processes contact this target during a period that is optimal for them to associate with the target, or when the reproductive tissue is most attractive to Rz processes, or both.
Visual-visual associative learning and reward-association learning in monkeys: the role of the amygdala
Authors: Gaffan D , Gaffan EA , Harrison S
Published: March 2018

Three Cynomolgus monkeys (Macaca fascicularis) took part in an experiment on visual learning set in an automatic apparatus. Each new visual discrimination problem was solved using a visual secondary reinforcer consisting of a white line. If the monkey chose the correct stimulus (by touching it), the white line appeared over the correct stimulus. Primary food reward was delivered only after a new problem was solved to a criterion, and the problem was then replaced by a new one. Thus, within-problem learning did not rely on primary reinforcement but on the visual secondary reinforcer. The animals were trained preoperatively in visual learning set with this procedure and were assessed postoperatively for their ability to learn new visual discriminations with the same procedure. Bilateral amygdalectomy did not significantly impair the animals' learning ability in this task. Learning remained unimpaired when transection of the uncinate fascicle and of the fornix was added to amygdalectomy. The effect of bilateral amygdalectomy in this task was much less severe than in a similar task we previously studied, with auditory secondary reinforcers. The results show that the involvement of the amygdala in processes of secondary reinforcement depends on the sensory properties of the secondary reinforcer. From these and other recent results, we conclude that the sensory attributes of a reinforcer are easily associated with a discriminative stimulus when they are in the same modality and same spatial location as the discriminative stimulus and that this sensory- sensory association is independent of the amygdala.
Postnatal development of corticocortical efferents from area 17 in the cat's visual cortex
Authors: Price DJ , Zumbroich TJ
Published: March 2018

We are interested in the postnatal development of corticocortical connections in the cat's visual cortex. In this study, we injected the anterograde tracer 3H-proline into visual cortical area 17 of kittens, aged 4–70 d, and adult cats to visualize the distribution of terminals of the association projections to areas 18, 19, 21a, and the lateral suprasylvian visual cortex. The density of anterograde label was quantified using computerized image analysis. There was dense labeling at topographically appropriate locations in area 18 in animals of all ages. In 4- and 8-d-old kittens, other extrastriate areas (19, 21a and the lateral suprasylvian cortex) contained only sparse label, localized in a few solitary axons; these areas were densely labeled in animals aged 12 d or more. In kittens aged 4–20 d there was considerable, widespread label within fibers located in the white matter, and many of these axons lay underneath regions of extrastriate, and also striate, cortex that were almost certainly not destined to be persistently innervated by cells at the injection site. This pattern of extensive white matter label was not seen in animals older than 20 d. In each extrastriate region, from the earliest age at which we identified dense cortical innervation from area 17, the terminals were distributed in clusters. At first these patches were mainly in infragranular layers, but later, during the second and third postnatal weeks, they began to appear in more superficial laminae. By 70 d, an adult-like distribution of terminals was found in each extrastriate area: most fibers appeared to end in layers II and III in areas 18, 19, and 21a and centered on layer IV in the medial bank of the middle suprasylvian sulcus in adult cats. We suggest that the development of ipsilateral association projections from area 17 to extrastriate cortex is a 2-stage process. First, cells at a particular point in area 17 send immature fibers in a nonspecific fashion through white matter towards a very wide area of extrastriate cortex. Second, corticocortical axons penetrate extrastriate cortex mainly in patches at topographically appropriate regions and grow to their targets in a specific fashion.
Human fetal mesencephalic tissue grafted to dopamine-denervated striatum of athymic rats: light- and electron-microscopical histochemistry and in vivo chronoamperometric studies
Authors: Stromberg I , Almqvist P , Bygdeman M , Finger TE , Gerhardt G , Granholm AC , Mahalik TJ , Seiger A , Olson L , Hoffer B
Published: March 2018

Human fetal mesencephalic tissue obtained from elective first-trimester abortions was grafted to 6-hydroxydopamine-denervated striatum of athymic (nude) rats. After 3–6 months, the transplants were evaluated by light and electron microscopy using antibodies against tryosine hydroxylase (TH), human specific Thy-1 (Thy-1), 5-hydroxytryptamine (5- HT), and laminin. In vivo chronoamperometric studies of K+-induced release of electroactive species were done prior to the histochemical evaluations. At the light microscopical level, Thy-1-immunoreactivity was evenly distributed throughout the entire transplants. Thy-1- immunoreactive nerve fibers were observed radiating from the graft into the host striatum. In sections that were double-stained with antibodies against Thy-1 and TH, such nerve fibers contained both markers. Also 5- HT-immunoreactive cells were found in the grafts with processes both in the grafts and radiating into host neuropil. Laminin immunohistochemistry showed an even distribution of capillaries in the graft with less density than in host brain, suggesting immaturity of graft tissue. At the ultrastructural level, TH-immunoreactive axons made symmetric contacts with unlabeled dendritic shafts and dendritic spines within the host brain. A few asymmetric contacts with TH- immunoreactive axons were seen. 5-HT-immunoreactive terminals made both symmetric and asymmetric contacts with unlabeled dendritic shafts and spines. In vivo chronoamperometry using local application of K+ revealed average signals that were lower on the transplanted side than in control striatum. However, close to the grafts significant amounts of the K+-evoked signal amplitudes were as large as 1.3 microM, and the ratio of the reduction to oxidation currents suggested release of a mixture of dopamine and 5-HT. Taken together, this study shows that human fetal mesencephalic tissue pieces survive grafting into nude rats, develop normal vascularization, and express coexistence of TH- and Thy-1-immunoreactivity. Human TH- and 5-HT-immunoreactive nerve fibers form synapses in host striatum and release monoamine neurotransmitters.
Remodeling of neuromuscular junctions in adult mouse soleus
Authors: Wigston DJ
Published: March 2018

The stability of neuromuscular junctions (NMJs) was studied in soleus muscles of adult mice by labeling acetylcholine receptors in vivo with rhodamine alpha-bungarotoxin. Identified NMJs were examined in living animals by low-light-level fluorescence microscopy on 2 or 3 occasions separated by up to 6 months. Many NMJs appeared identical each time they were viewed except for overall enlargement probably related to growth of the animal. Forty-four percent of NMJs, however, changed their shape over 6 months; these changes consisted mostly of small deletions or additions to part of the initial configuration. NMJs in adult soleus appeared to be less malleable than suggested by earlier studies but more plastic than NMJs in another muscle, the mouse sternomastoid, in which virtually no remodeling was observed using similar methods to the present study (Lichtman et al., 1987a). Thus, the degree of remodeling at NMJs may vary among different muscles, perhaps depending on their pattern of use.
Amacrine cell interactions underlying the response to change in the tiger salamander retina
Authors: Maguire G , Lukasiewicz P , Werblin F
Published: March 2018

The neural circuitry and pharmacology underlying transient signal formation at the bipolar-amacrine cell interface were studied. Synaptic currents were measured with whole cell patch clamp in retinal slices. Cell types were identified with Lucifer yellow staining. Activity was initiated with puffs of kainate of known time course and spatial spread delivered at bipolar dendrites. OFF bipolar cells responded to kainate with a sustained inward current, but ON bipolar cells were silent. Two types of amacrine cell were found: (1) narrow field cells, with processes that extended laterally less than 200 microns, responding with a sustained inward current, and (2) wide field cells, with processes that extended laterally by up to 1 mm, responding with a brief transient inward current followed by a more sustained outward current. We pharmacologically dissected the synaptic interactions underlying the transient current in the wide field amacrine cell. In the presence of 5-aminovaleric acid (AVA), the time course of this transient current was increased so that it resembled the response of bipolar cells. Because AVA is a GABAB antagonist, it appears to block an opposing signal that truncates the sustained excitatory bipolar input, thereby generating the transient. GABAB specificity is confirmed by (1) block of the transient inward current by baclofen, a GABAB agonist, and (2) block of the baclofen effect by AVA. The site of GABAB action appears to be presynaptic to the amacrine cell membrane because neither baclofen nor AVA, in combination with picrotoxin, had a direct effect at the amacrine cell membrane. GABAB receptors are often found at presynaptic terminals where they modulate calcium or potassium conductances. It has been shown that bipolar cell terminals receive a GABAergic synaptic input (Vaughn et al., 1981; Wu et al., 1981; Tachibana and Kaneko, 1987). The narrow field sustained-responding amacrine cells appear to be GABAergic (Werblin et al., 1988). This suggests that transient activity measured in wide field amacrine cells is formed at a population of bipolar cell terminals by GABAergic feedback from narrow field amacrine cells at GABAB receptors.
Androgen-specific critical periods for the organization of the major pelvic ganglion
Authors: Melvin JE , Hamill RW
Published: March 2018

Previous studies indicate that the major pelvic ganglion (PG) is dependent on testosterone for normal development. Tyrosine hydroxylase (T-OH), DOPA decarboxylase, and choline acetyltransferase (CAT) activities are significantly reduced by postnatal castration on day 10- 11, while testosterone replacement therapy reversed all developmental enzyme activity deficits (Melvin and Hamill, 1987). In the present studies castration on the day of birth combined with various testosterone-replacement paradigms produced effects demonstrating that the PG is sensitive to testosterone dosage and time of administration during early postnatal development. Gonadal hormone replacement experiments show that the androgens testosterone and dihydrotestosterone were effective in restoring T-OH and CAT activity deficits produced by neonatal castration. Estrogen therapy reversed the deficits in CAT activity, but was ineffective in reversing the alterations in T-OH activity. Treatment of pregnant dams with the anti- androgen flutamide altered the ontogeny of T-OH and CAT activities in pups despite replacement therapy on the day of birth. Thus, androgen- critical periods exist prenatally as well as postnatally. These studies suggest that the organization of PG development is critically dependent on both the time of exposure and dose of testosterone. Prenatal and postnatal critical periods appear to exist. In addition, the lack of an effect of estradiol on tyrosine hydroxylase activity suggests that androgens are specifically responsible for organizing the noradrenergic development of the PG.
Evidence that glycine mediates the postsynaptic potentials that inhibit lumbar motoneurons during the atonia of active sleep
Authors: Chase MH , Soja PJ , Morales FR
Published: March 2018

Postsynaptic inhibition of somatic motoneurons underlies the atonia of active sleep. This inhibitory control depends, in large measure, on the bombardment of motoneurons during active sleep by a unique class of large-amplitude inhibitory postsynaptic potentials (IPSPs). These potentials are present only during this behavioral state and have therefore been designated as active sleep-specific IPSPs (AS-IPSPs). The present study was concerned with determining the neurotransmitter that mediates these AS-IPSPs. Lumbar motoneurons were recorded intracellularly during quiet and active sleep in intact, undrugged, normally respiring cats. The frequency and waveform parameters of the inhibitory postsynaptic potentials recorded from these motoneurons were examined following the microiontophoretic juxta-cellular administration of strychnine (a glycine receptor antagonist) and picrotoxin and bicuculline (GABA receptor antagonists). Microiontophoretically applied strychnine abolished the AS-IPSPs and a majority of smaller-amplitude IPSPs. Neither picrotoxin nor bicuculline modified the frequency, amplitude, or rising phase of the AS-IPSPs or the smaller-amplitude IPSPs. We conclude that the postsynaptic inhibitory drive that impinges on motoneurons during active sleep is principally mediated by glycine or a glycinergic substance.
Vasopressin neuromodulation in the hippocampus
Authors: Brinton RE , McEwen BS
Published: March 2018

This study explored an effector mechanism associated with the arginine vasopressin (AVP) recognition site in the hippocampus, namely, potentiation of norepinephrine (NE)-induced cAMP accumulation in the surviving hippocampal slice. The biochemical mechanisms that underlie the AVP potentiation were investigated as follows: First, the actions of AVP upon NE-induced accumulation of cAMP in hippocampal slices from rat brain were specific to AVP and not shared by other closely related peptides, namely, oxytocin and AVP4–9. Second, the AVP-induced neuromodulation involved beta-adrenergic receptors, with AVP having no effect on cAMP levels in the absence of NE. Third, the potentiation by AVP was biphasic, with lower AVP concentrations potentiating NE-induced cAMP accumulation, while higher concentrations did not potentiate. Fourth, an antagonist of V1-type AVP receptors blocked AVP potentiation. Fifth, AVP potentiation was dependent upon extracellular calcium concentrations. Sixth, AVP potentiation was blocked by 50 microM trifluoperazine, which is consistent with a calcium-calmodulin involvement but which might also implicate protein kinase C. These alternatives and the nature of the calcium involvement are discussed. AVP actions thus appear to involve interactions between several second- messenger systems and suggest a biochemical mechanism by which AVP exerts its centrally mediated behavioral effects.
Stable and dynamic forms of cytoskeletal proteins in slow axonal transport
Authors: Tashiro T , Komiya Y
Published: March 2018

Dynamic organization of the axonal cytoskeleton was investigated by analyzing slow axonal transport of tubulin and other major cytoskeletal proteins in the motor axons of rat sciatic nerve 1–4 weeks after injection of L-35S-methionine into the anterior horn area of L3-L5 lumbar spinal cord. A large proportion (50–65%) of tubulin transported in the axon was found to be insoluble when extracted with 1% Triton at 4 degrees C. This cold-insoluble tubulin was also resistant to other microtubule-destabilizing agents such as Ca2+, colchicine, and nocodazole, suggesting that it corresponded to the stably polymerized tubulin specific to the axon. From the cold-soluble fraction, microtubules containing a distinct set of associated proteins were recovered by the taxol-dependent procedure. Transport pattern of cold- soluble and -insoluble tubulin in this system showed a time-dependent broadening of the tubulin wave resulting in the appearance of a new faster wave enriched in cold-soluble tubulin. The slower and the faster waves of tubulin were defined as group V or slow component a (SCa) and group IV or slow component b (SCb), respectively, with respect to the 2 subcomponents of slow transport originally described in the optic system. However, compositions of groups IV and V in sciatic motor axons differed significantly from those of the optic system. Actin also exhibited a clear dual wave pattern of transport that coincided well with that of tubulin, indicating that both actin and tubulin were the major components of both groups IV and V.(ABSTRACT TRUNCATED AT 250 WORDS)
Astrocytes cultured from mature brain derive from glial precursor cells
Authors: Norton WT , Farooq M
Published: March 2018

We have previously shown that enriched preparations of oligodendrocytes from either mature bovine brain or 30-d-old rat brain, when cultured in serum-free medium, yield mixed cultures of oligodendrocytes and astrocytes even though no GFAP+ cells were present after 24 hr in culture (Norton et al., 1986, 1988). To test the possibility that the astrocytes in these cultures arose from glial precursor cells, we followed the expression of ganglioside GD3, galactosylceramide (GC), glial fibrillary acidic protein (GFAP), and vimentin in the cultures. GD3 has already been shown to be a marker of immature neuroectodermal cells, which in the postnatal brain are glial progenitor cells (Goldman et al., 1984, 1986). The cultures from both species contained at 1 DIV only two populations of cells; 90–95% GC+/GD3- oligodendrocytes and 4– 10% GD3+/GC- small, round cells. With time, the oligodendrocytes remained GD3-/GFAP-/vimentin-. The kinetics of antigen expression of the GD3+ cells could best be interpreted by the following sequence: (sequence; see text) We interpret these results to show that the astrocytes arose from a small population of GD3+ glial precursor cells present in the brain that were co-isolated with oligodendroglia. No evidence was obtained that these GD3+ cells could also differentiate into oligodendrocytes.
The effects of postsynaptic levels of cyclic AMP on excitatory and inhibitory responses of an identified central neuron
Authors: Wolszon LR , Faber DS
Published: March 2018

The effects of cAMP on Mauthner (M-) cell excitatory and inhibitory responses were studied in vivo. Cyclic AMP was iontophoresed into the M- cell lateral dendrite, after which we monitored the changes in cellular responsiveness to stimulation of 2 classes of identified presynaptic cells: (1) excitatory fibers from the posterior branch of the ipsilateral eighth cranial nerve and (2) inhibitory interneurons activated by the M-cell collateral and commissural networks. We found that postsynaptic injections of cAMP increased the magnitudes of the electrically and chemically mediated EPSPs from the eighth nerve and enhanced M-cell inhibitory responses as well. Furthermore, cAMP augmented paired-pulse facilitation of both types of excitatory potentials. No effects on input conductance, resting membrane potential, or presynaptic spike width were observed. All effects were mimicked by aminophylline, a cAMP-dependent phosphodiesterase inhibitor but not by 5′-AMP, the cAMP breakdown product. These results provide evidence for second-messenger modulation in vivo of electrotonic and chemical synaptic potentials at mixed synapses. In addition, they provide the first evidence for cAMP modification of a glycinergic receptor-channel complex. Preliminary results from some of these experiments have been reported previously (Wolszon and Faber, 1986).
Apical localization of the alpha subunit of GTP-binding protein Go in choroidal and ciliated ependymocytes [published erratum appears in J Neurosci 1989 Apr;9(4):following Table of Contents]
Authors: Peraldi S , Nguyen Than Dao B , Brabet P , Homburger V , Rouot B , Toutant M , Bouille C , Assenmacher I , Bockaert J , Gabrion J
Published: March 2018

The presence of GTP-binding proteins (G proteins) has been studied in murine adult choroid plexuses and cultured fetal choroidal or hypothalamic ependymal cells by ADP-ribosylation catalyzed by Bordetella pertussis toxin (PTX) and by immunodetection using affinity- purified polyclonal antibodies against the alpha subunit of the Go protein (Go alpha), the major brain G protein. ADP-ribosylation with 32P-NAD and PTX of choroid plexus revealed an intense labeling at the 40 kDa level in addition to the known PTX-substrates at 41 kDa (Gi alpha) and 39 kDa (Go alpha). This 40 kDa substrate was also predominant in cultured ependymal cells. However, a positive immunoreactivity with the anti-Go alpha antibodies was detected at the level of the 39 kDa faster component, indicating the presence of Go alpha in both choroid plexuses and cultured ependymal cells. In thin frozen sections as well as in cultured cells, Go alpha was mainly immunolocalized at the apical pole of choroidal ependymocytes and in the kinocilia of ciliated ependymal cells. At the ultrastructural level, using gold immunoprobes, the immunoreactivity of a Go alpha-like protein was detected on the cytoplasmic face of the apical plasma membrane, coated pits and vesicles, and in the apical cytoplasmic matrix. In ciliated ependymal cells, the positive immunostaining displayed a dotted pattern at the surface of demembranated axonema of apical kinocilia. These findings strongly suggest that G proteins, especially Go, are involved in transducing chemical signals that modulate traffic and exchanges between cerebrospinal fluid and ependyma through the apical membrane of ependymocytes.
The neurology of memory: quantitative assessment of retrograde amnesia in two groups of amnesic patients
Authors: Squire LR , Haist F , Shimamura AP
Published: March 2018

The phenomenon of retrograde amnesia has important implications for understanding normal memory as well as its neural organization. Using 6 tests of remote memory, we evaluated the extent and severity of retrograde amnesia in 2 groups of amnesic patients--7 patients with alcoholic Korsakoff's syndrome and 5 other patients with amnesia (anoxia or ischemia, N = 3; thalamic infarction, N = 1; unknown etiology, N = 1). Although there were individual differences, Experiment 1 showed that the severity and extent of retrograde amnesia was similar for the 2 groups. Retrograde amnesia was temporally graded across a period of about 15 years and was not detectable in more remote time periods. In Experiment 2, repeated testing during a 3 year period showed that amnesic patients and control subjects were similarly consistent in their responses. Amnesic patients did not catch up to control subjects by eventually accumulating as many correct answers as the control subjects. In Experiment 3, amnesic patients performed normally on a test of very difficult general information questions, which were based on material likely to have been learned long ago. In all 3 experiments, the 2 groups of amnesic patients performed similarly. The results support the following conclusions: (1) Extensive, temporally graded retrograde amnesia, which has been observed frequently in patients with Korsakoff's syndrome, occurs readily in other amnesic patients as well, even when their memory impairment appears well circumscribed; (2) patients with presumed damage to either the medial temporal or the diencephalic brain structures linked to memory functions can produce a similar kind of retrograde amnesia; (3) the impairment reflects a loss of usable knowledge, not simply difficulty accessing an intact memory store that can then be overcome given sufficient retrieval opportunities; (4) very remote memory, at least for factual information, can be intact in amnesia; (5) the structures damaged in amnesia support memory storage, retrieval, or both during a lengthy period of reorganization, after which representations in memory can become independent of these structures.