bluuebunny/crossref_metadata_2025 huggingface dataset:
Anatomy and physiology of a color system in the primate visual cortex
Authors: Livingstone MS , Hubel DH
Published: March 2018

Staining for the mitochondrial enzyme cytochrome oxidase reveals an array of dense regions (blobs) in the primate primary visual cortex. They are most obvious in the upper layers, 2 and 3, but can also be seen in layers 4B, 5, and 6, in register with the blobs in layers 2 and 3. We compared cells inside and outside blobs in macaque and squirrel monkeys, looking at their physiological responses and anatomical connections. Cells within blobs did not show orientation selectivity, whereas cells between blobs were highly orientation selective. Receptive fields of blob cells had circular symmetry and were of three main types, Broad-Band Center-Surround, Red-Green Double-Opponent, and Yellow-Blue Double-Opponent. Double-Opponent cells responded poorly or not at all to white light in any form, or to diffuse light at any wavelength. In contrast to blob cells, none of the cells recorded in layer 4C beta were Double-Opponent: like the majority of cells in the parvocellular geniculate layers, they were either Broad-Band or Color- Opponent Center-Surround, e.g., red-on-center green-off-surround. To our surprise cells in layer 4C alpha were orientation selective. In tangential penetrations throughout layers 2 and 3, optium orientation, when plotted against electrode position, formed long, regular, usually linear sequences, which were interrupted but not perturbed by the blobs. Staining area 18 for cytochrome oxidase reveals a series of alternating wide and narrow dense stripes, separated by paler interstripes. After small injections of horseradish peroxidase into area 18, we saw a precise set of connections from the blobs in area 17 to thin stripes in area 18, and from the interblob regions in area 17 to interstripes in area 18. Specific reciprocal connections also ran from thin stripes to blobs and from interstripes to interblobs. We have not yet determined the area 17 connections to thick stripes in area 18. In addition, within area 18 there are stripe-to-stripe and interstripe- to-interstripe intrinsic connections. These results suggest that a system involved in the processing of color information, especially color-spatial interactions, runs parallel to and separate from the orientation-specific system. Color, encoded in three coordinates by the major blob cell types, red-green, yellow-blue, and black-white, can be transformed into the three coordinates, red, green, and blue, of the Retinex algorithm of Land.
Receptive field properties in the cat's area 17 in the absence of on- center geniculate input
Authors: Sherk H , Horton JC
Published: March 2018

Most neurons of area 17 in the cat respond to both light and dark stimuli, and it is often assumed that these responses originate from the on-center and off-center cells, respectively, of the lateral geniculate nucleus. This has not been demonstrated experimentally, however. Whether the on and off pathways make unique contributions to some of the response properties characteristic of visual cortex, such as orientation selectivity, is also unknown. The aim of these experiments was to investigate these questions by inactivating the retinogeniculate on pathway. In cats in which D,L-2-amino-4- phosphonobutyric acid (APB) had been injected into one eye, we found that, in the geniculate layers driven by that eye, there were no cells with on-center responses (Horton, J. C., and H. Sherk (1984) J. Neurosci. 4: 374–380). The on pathway appeared to have been inactivated. To see how cortical receptive fields were affected, we examined 184 binocular cells in area 17 contralateral to the injected eye. Each cell still had a normal receptive field in the ipsilateral eye, and we compared the cell's response properties in that eye with those in the eye injected with APB to assess the drug's effects. Overall responsiveness in the injected eye was severely reduced, and responses to the onset of stationary light stimuli were almost entirely abolished. Responses to moving light edges were weak or absent in most cells but still strong in a few; simple cells tended to have more vigorous light edge responses than complex cells. The general reduction in responsiveness, and the specific reduction in light edge responses, indicated that the on and off pathways both contribute (directly or indirectly) to the responses of most cells in area 17. The remaining responses to light edges we think originated mainly from the on- surrounds of off-center geniculate cells. Responses to moving dark edges were somewhat depressed compared to those in the normal eye. There was, however, no systematic change in direction selectivity and no reduction in specificity for orientation or length. In general, receptive field properties remained surprisingly normal despite the conspicuous reduction in responsiveness.
Differential subcellular localization of tubulin and the microtubule- associated protein MAP2 in brain tissue as revealed by immunocytochemistry with monoclonal hybridoma antibodies
Authors: Caceres A , Binder LI , Payne MR , Bender P , Rebhun L , Steward O
Published: March 2018

The distribution and subcellular localization of tubulin and MAP2 in brain tissue were analyzed by immunocytochemistry with monoclonal hybridoma antibodies prepared against Chinese hamster brain tubulin and MAP2. We examined three anti-tubulin hybridoma antibodies (Tu3B, Tu9B, Tu12) specific for beta-tubulin, and two anti-MAP2 hybridoma antibodies (AP9,AP13). The specificity of each of the monoclonal antibodies was characterized by staining nitrocellulose electrophoretic blots of SDS- polyacrylamide gels of whole brain or hippocampal extracts. Each hybridoma antibody bound only its respective antigen in these preparations. Polyclonal antisera against tubulin were also examined. Sections reacted with antisera against tubulin or monoclonal antibodies against beta-tubulin revealed a wide variety of stained cellular compartments. The reaction product was found to decorate dendritic and axonal microtubles in neurons; glial cells were also stained. MAP2 immunoreactivity was found only in neurons. In the case of one of the monoclonal antibodies (AP9), staining was preferentially associated with dendritic processes. However, light but significant staining of axonal processes was seen with AP13. Within dendrites, MAP2 was found associated with dendritic microtubules and postsynaptic densities (psd), both in shaft and spine synapses. In addition, strong immunoreactivity for MAP2 was found within the cytoplasm of dendritic spines. There was little or no immunoreactivity for tubulin in the spine cytoplasm, although the psd was stained. The localization of MAP2 in dendritic spines and in the psd suggests that this protein may have a biological role independent of its association with microtubules. The observations on differential staining of the hybridoma antibodies against MAP2 suggest that there may be distinct subtypes or states of MAP2 within neurons.
Teleost luteinizing hormone-releasing hormone: action on bullfrog sympathetic ganglia is consistent with role as neurotransmitter
Authors: Jones SW , Adams PR , Brownstein MJ , Rivier JE
Published: March 2018

Bullfrog sympathetic ganglion neurons have a “late, slow” excitatory postsynaptic potential (EPSP) that is mediated by a peptide similar to mammalian luteinizing hormone-releasing hormone (M-LHRH) (Jan, Y. N., L. Y. Jan, and S. W. Kuffler (1979) Proc. Natl. Acad. Sci. U. S. A. 76: 1501–1505). On biochemical evidence (Eiden, L. E., E. Loumaye, N. Sherwood, and R. L. Eskay (1982) Peptides 3:323–327) the endogenous LHRH-like peptide in the ganglion may be identical to teleost LHRH (T- LHRH; [Trp7,Leu8]M-LHRH) (Sherwood, N., L. Eiden, M. Brownstein, J. Speiss, J. Rivier, and W. Vale (1983) Proc. Natl. Acad. Sci. U. S. A. 80: 2794–2798). We have found that T-LHRH acts qualitatively like M- LHRH on bullfrog ganglion cells, but it is quantitatively more potent. As for M-LHRH, the primary action of T-LHRH under single-electrode voltage clamp is to inhibit the M-current, a voltage-dependent potassium current that is active in the region between rest and threshold in these cells. The M-current is also inhibited during the late, slow EPSP. Both T-LHRH and the late, slow EPSP can also induce an additional inward current, associated with an increased conductance, in some cells. An LHRH antagonist is effective against both T-LHRH and the late, slow EPSP. These results are consistent with a role for T-LHRH as the natural transmitter for the late, slow EPSP in bullfrog sympathetic ganglia.
Retinal ganglion cell terminals change their projection sites during larval development of Rana pipiens
Authors: Reh TA , Constantine-Paton M
Published: March 2018

Interconnecting neuronal populations in the vertebrate CNS are typically not well matched in their overall topographic patterns of histogenesis and differentiation during development. One striking example of this mismatch is the retinotectal system of the frog, where the retina grows in concentric annuli, while the optic tectum, a major retinal target, adds new neurons at only the caudo-medial border. The retinal ganglion cell (RGC) terminals nevertheless form an organized map in the tectum during the period when the two structures are undergoing such disparate modes of growth. This led Gaze et al. (Gaze, R. M., M. J. Keating, and S. H. Chung (1974) Proc. R. Soc. Lond. (Biol.) 185: 301–330) to propose that the terminals must shift caudally during development. In the present study, we have directly tested the hypothesis of “shifting connections” by selectively labeling an identified population of RGC terminals, those at the optic nerve head (ONH), and determining their tectal projection site relative to a particular group of [3H]thymidine-labeled tectal neurons. With this double-label technique, we have found that RGC terminals from cells at the ONH move from a position rostral to the [3H]thymidine-labeled tectal cells to a position caudal to these same cells during the latter half of larval development. This represents a movement of approximately 1.4 mm across the tectal surface between stages T&K XII and T&K XXV. In addition, we have used electron microscopy and electrophysiology to demonstrate that the RGC terminals make functional synaptic connections during this period. This indicates that RGC terminals continually change the tectal neurons with which they form functional synapses during the development of the retinotectal system. We propose that such moving, but highly ordered connections can best be explained by a two stage mechanism for map formation, in which graded selective adhesions between cells in appropriate regions of retina and tectum provide the overall gross retinotopy of the projection, while competitive interactions between RGC terminals are responsible for the refinement of the precision in this system.
Tonic vasomotor control by the rostral ventrolateral medulla: effect of electrical or chemical stimulation of the area containing C1 adrenaline neurons on arterial pressure, heart rate, and plasma catecholamines and vasopressin
Authors: Ross CA , Ruggiero DA , Park DH , Joh TH , Sved AF , Fernandez-Pardal J , Saavedra JM , Reis DJ
Published: March 2018

We have studied the responses to electrical and chemical stimulation of the ventrolateral medulla in the chloralose-anesthetized, paralyzed, artificially ventilated rat. Locations of most active pressor responses were compared to regions containing neurons labeled immunocytochemically for phenylethanolamine N-methyltransferase (PNMT), the enzyme catalyzing the synthesis of adrenaline. Elevations of arterial pressure (+81.6 +/- 2.5 mm Hg) and cardioacceleration (+73 +/- 13.6 bpm) were elicited with low current (5 times threshold of 9.5 +/- 1.1 microA) electrical stimulation in a region of rostral ventrolateral medullary reticular formation we have termed the nucleus reticularis rostroventrolateralis (RVL). Electrical stimulation of the RVL increased plasma catecholamines (16.8-fold for adrenaline, 5.3-fold for noradrenaline, and 1.9-fold for dopamine) and vasopressin (1.7-fold before spinal transection, 4.7-fold after). The location of the most active pressor region in the ventrolateral medulla corresponded closely with the location of C1 adrenaline-synthesizing (PNMT-containing) neurons. In addition, the location of the most active pressor region in the dorsomedial medulla corresponded with the location of a bundle of PNMT-containing axons. Unilateral injections into the RVL of the excitatory amino acid monosodium L-glutamate (50 pmol to 10 nmol), but not saline, caused transient dose-dependent and topographically specific elevations (maximum +71.6 +/- 4.9 mm Hg) of arterial blood pressure and tachycardia. Injections of the rigid structural analogue of glutamate, kainic acid, caused large, prolonged (at least 15 min) pressor responses and tachycardia. Unilateral injections of the inhibitory amino acid gamma-aminobutyric acid (GABA) into the RVL caused transient dose-dependent hypotension (maximum -40.8 +/- 6.6 mm Hg) and bradycardia, whereas the specific GABA antagonist bicuculline caused prolonged (10 to 20 min) elevations (+64.2 +/- 6.8 mm Hg) of arterial pressure and tachycardia. By contrast, injections of the glycine antagonist strychnine had no significant effect. Bilateral injections of the neurotoxin, tetrodotoxin, dropped arterial pressure to low levels (51.7 +/- 4.7) not changed by subsequent spinal cord transection at the first cervical segment (52.5 +/- 6.2). We propose the following. (1) Neurons within the RVL, most probably C1 adrenaline- synthesizing neurons, exert an excitatory influence on sympathetic vasomotor fibers, the adrenal medulla, and the posterior pituitary. (2) These neurons are tonically active and under tonic inhibitory control, in part via GABAergic mechanisms--perhaps via the nucleus of the solitary tract (NTS).(ABSTRACT TRUNCATED AT 400 WORDS)
The acetylcholine receptor channel from Torpedo californica has two open states
Authors: Labarca P , Lindstrom J , Montal M
Published: March 2018

We recorded single channel currents activated by agonist binding to purified acetylcholine receptors from the electric organ of Torpedo californica reconstituted in planar lipid bilayers. Analysis of single channel records indicate that the acetylcholine receptor channel displays two kinetically distinct open states which differ in their mean open times but have similar channel conductances.
Muscarinic receptors: evidence for a nonuniform distribution in tracheal smooth muscle and exocrine glands
Authors: Basbaum CB , Grillo MA , Widdicombe JH
Published: March 2018

Muscarinic receptor distribution in smooth muscle, exocrine glands, and epithelium of the ferret trachea was determined using [3H]propylbenzilylcholine mustard ([3H]PrBCM) binding and autoradiography. Specific, atropine-sensitive [3H]PrBCM binding was quantified autoradiographically in the trachealis muscle (approximately 21 binding sites/microns2), surface epithelium (approximately 6 binding sites/microns2), and submucosal glands (approximately 5 binding sites/microns2). Serous and mucous cells in the glands did not differ in receptor density. Binding sites on gland and epithelial cells were associated with basolateral membranes. In the trachealis muscle, a gradient in receptor density was observed, with outer layers of muscle containing 3 to 10 times more receptors per unit area than inner layers. Receptor distribution in both glands and muscle paralleled the distribution of cholinergic axons. However, at the light microscope level, there was no evidence for the presence of receptor “hot spots” related to the position of individual axons. The parallelism in the distribution of axons and receptors suggests the possibility of neural control of the genesis and/or maintenance of receptor distribution in these tissues.
Effect of cholecystokinin-octapeptide on dopamine release from slices of cat caudate nucleus
Authors: Markstein R , Hokfelt T
Published: March 2018

The cat caudate nucleus has been reported to possess a rich and fairly even distribution of nerve endings, containing both dopamine- and cholecystokinin-like peptides. In this study, the effect of cholecystokinin-octapeptide (CCK-8) on basal and electrically evoked tritium outflow from slices of cat caudate nucleus previously labeled with [3H]dopamine was examined. Evoked tritium outflow from slices of cat caudate nucleus was Ca2+ dependent and abolished by tetrodotoxin, suggesting that it reflects action potential-induced [3H]dopamine release. In the presence of bovine serum albumin and bacitracin, the sulfated but not the unsulfated form of CCK-8 inhibited both basal and electrically evoked tritium outflow from slices of cat caudate nucleus at very low concentrations. CCK-8 sulfate was efficient in causing this effect in concentrations down to 10(-14) M, and the maximum effect was obtained with 10(-11) M. In contrast, without bovine serum albumin and bacitracin, no inhibitory effect of CCK-8 sulfate was seen, but instead, a marked enhancement of tritium outflow at 10(-7) M was observed. The findings suggest that CCK-8 sulfate in dopamine/CCK coexistence regions is involved in regulating dopamine release.
Fibrous and protoplasmic astrocytes are biochemically and developmentally distinct
Authors: Miller RH , Raff MC
Published: March 2018

We have studied semithin frozen sections of developing and adult rat central nervous system (CNS) by indirect immunofluorescence in order to determine the antigenic phenotype of protoplasmic and fibrous astrocytes. Using antibodies against glial fibrillary acidic protein (GFAP) to identify astrocytes, we show that the great majority of fibrous astrocytes in adult optic nerve are labeled by the monoclonal antibody A2B5, while the great majority of protoplasmic astrocytes in adult cerebral cortex are not. Astrocytes located at the periphery of the adult optic nerve that form the glial limiting membrane are more like protoplasmic astrocytes than fibrous astrocytes in that they strain relatively weakly with anti-GFAP antiserum and are A2B5-. In the developing rat optic nerve, protoplasmic-like astrocytes appear at least one week before the first fibrous astrocytes can be detected. Taken together with our previous observations on astrocytes in suspensions and cultures of developing rat optic nerve (Raff, M.C., E.R. Abney, J. Cohen, R. Lindsay, and M. Noble (1983) J. Neurosci. 3: 1289–1300; Raff, M.C., R.H. Miller, and M. Noble (1983) Nature 303: 390– 396), these results suggest that protoplasmic and fibrous astrocytes are distinct classes of glial cells that differ in their antigenic phenotype and developmental history, as well as in their morphology and location within the CNS.
Peripheral-type benzodiazepine receptors in the central nervous system: localization to olfactory nerves
Authors: Anholt RR , Murphy KM , Mack GE , Snyder SH
Published: March 2018

Binding levels of [3H]Ro5–4864, a ligand selective for peripheral-type benzodiazepine receptors, are substantially higher in homogenates of the olfactory bulb than in the rest of the brain. Among peripheral tissues evaluated, high levels of [3H]Ro5–4864 binding are found in the nasal epithelium. Drug displacement studies show that these binding sites are pharmacologically of the peripheral type. Their presence in the nasal epithelium and in the olfactory bulb can be demonstrated in several different mammalian species. Autoradiographic studies of murine nose reveal a bipolar staining pattern around the cell bodies of the olfactory receptor cells, suggesting the presence of peripheral-type benzodiazepine receptors on both processes of these bipolar neurons. In the brain a high density of [3H]Ro5–4864 binding sites occurs in the nerve fiber and glomerular layers of the olfactory bulb. Throughout the rest of the brain [3H]Ro5–4864-associated silver grains are diffusely distributed with intense staining over the choroid plexus and along the ependymal linings of the ventricles. Both the distribution and the ontogenic development of the peripheral-type benzodiazepine receptors differ from the central-type receptors. Intranasal irrigation with 5% ZnSO4 results in a 50% reduction of peripheral-type benzodiazepine receptors in the olfactory bulb without affecting the density of central-type benzodiazepine receptors. Thus, [3H]Ro5–4864 binding sites in the olfactory bulb appear in large part to be localized to olfactory nerves which originate in the nasal epithelium.
A transient potassium conductance regulates the excitability of cultured hippocampal and spinal neurons
Authors: Segal M , Rogawski MA , Barker JL
Published: March 2018

Cultured mouse spinal cord and rat hippocampal neurons were voltage clamped with a two-electrode system in the presence of tetrodotoxin (1 to 3 microM) and tetraethylammonium (25 mM). Depolarizing voltage commands from holding potentials negative to -50 mV evoked a transient outward current response that peaked within 10 msec and decayed exponentially with a time constant of 10 to 40 msec. The current was inactivated by holding at potentials more positive than -50 mV but could be reactivated by brief hyperpolarizing prepulses (20-msec steps to -90 mV reactivated 50%). The inversion potential of the tail current evoked in a double-step protocol was -70 to -75 mV, and this shifted in a depolarizing direction with elevated [K+]0. The transient outward current was blocked by external application of 4-aminopyridine (4-AP) with an IC50 of 2 mM. In experiments under current clamp, 4-AP suppressed an initial transient rectification of the electrotonic potential recorded in response to depolarizing current and reduced the threshold for single and repetitive action potentials. Thus, a transient K+ conductance similar to IA of molluscan neurons may serve to regulate the excitability of some central mammalian neurons. Depression of this conductance by 4-AP could contribute to the drug's convulsant effects in vivo.
Serotonin-induced protein phosphorylation in a lobster neuromuscular preparation
Authors: Goy MF , Schwarz TL , Kravitz EA
Published: March 2018

Three substances believed to be neurohormones in the lobster-- serotonin, octopamine, and proctolin--can modulate the physiology of the dactyl opener muscle of the lobster walking leg. All three act directly on muscle fibers to cause long-lasting contractures. In addition, serotonin enhances the release of transmitter from the excitatory and inhibitory axons that innervate the muscle. We now report that serotonin, applied to intact nerve-muscle preparations, increases the phosphorylation of a soluble 29,000-dalton protein by as much as 20-fold. In two respects the phosphorylation parallels the physiological effects of serotonin: both have a slow time course, and both are caused by low concentrations of serotonin (thresholds of approximately 10(-8) M). The 29,000-dalton protein is present in many lobster tissues, including thoracic ganglia, gills, and several different muscles. This suggests that the phosphorylation participates in some aspect of metabolism common to many types of cells, rather than in an activity unique to nerve or muscle. The function of the phosphorylated protein remains unknown. Several lines of evidence suggest that the phosphorylation is mediated by a cyclic nucleotide, probably cyclic AMP. (1) Adding cyclic AMP or cyclic GMP to nerve- muscle homogenates leads to the phosphorylation. (2) Adding 8-Br-cyclic AMP or 8-Br-cyclic GMP to intact preparations leads to the phosphorylation. (3) In intact tissue, forskolin, an adenylate cyclase activator, and isobutylmethylxanthine, a phosphodiesterase inhibitor, increase cyclic AMP and cyclic GMP and also cause the phosphorylation. (4) Serotonin increases cyclic AMP in intact preparations. (5) RMI 12,330A, which blocks the serotonin-induced cyclic AMP increase, also blocks the phosphorylation. (6) Serotonin has no detectable effect on cyclic GMP. This suggests that cyclic AMP, and not cyclic GMP, is the second messenger that mediates phosphorylation in vivo. In contrast, calcium is not likely to mediate the phosphorylation. Agents that block calcium channels do not block the serotonin-induced phosphorylation, and agents that increase sarcoplasmic calcium do not cause it. Furthermore, calcium does not induce the phosphorylation in a homogenate. One of the other modulators, proctolin, does not increase cyclic AMP or cause the phosphorylation even at concentrations 10(6)- fold greater than the hormone's threshold for producing contractures. The third modulator, octopamine, causes small increases in cyclic AMP and is a weak agonist of the phosphorylation. Neither proctolin nor octopamine alters cyclic GMP levels.
Effects of sensory deprivation on the developing mouse olfactory system: a light and electron microscopic, morphometric analysis
Authors: Benson TE , Ryugo DK , Hinds JW
Published: March 2018

Closure of the nostril by electrocauterization on postnatal day (PN) 1 or 2 was used to study effects of olfactory deprivation on developing olfactory epithelium (OE) and bulb (OB) in CD-1 mice. No damage was observed in OE sections 1 or 3 days after closure, and at PN 30 no difference was found in the number of OE receptors between closed and open sides. Odor deprivation and a decrease in functional activity in experimental bulbs was evident from deoxyglucose autoradiographs at PN 21 and PN 30. At PN 30 deprived bulbs appeared smaller than nondeprived bulbs. Nissl stains revealed normal cytoarchitecture, but a protargol stain demonstrated fewer intraglomerular dendrites in deprived bulbs. At PN 30, volumes of deprived bulbs were 26% smaller than nondeprived bulbs. The volume of each bulbar lamina was 13 to 35% smaller than the comparable nondeprived lamina except for the ventricular/subependymal zone which was not significantly different between bulbs. Volumes of bulbs contralateral to the closed naris and the volumes of their laminae were not significantly different from control bulbs, suggesting no hypertrophy of nondeprived laminae. Deprivation did not affect the number of mitral cells seen at PN 30, their nuclear size, or their number of nucleoli. Lateral olfactory tract cross-sectional area was also unaffected by deprivation. Mitral cell perikaryal size, however, was smaller in deprived bulbs. Soma surface areal density of deprived mitral-to-granule cell synapses in deprived bulbs was 65% of the nondeprived density, while the density of granule-to-mitral cell synapses was only 46% of the nondeprived density. It is concluded that neonatal naris closure brings about a functional deprivation of the OB without receptor degeneration. Neonatal olfactory deprivation affects the perikaryal surface area but not the number of mitral cells. Also, deprivation markedly affects the reciprocal synapses between mitral and granule cells. Olfactory sensation thus appears necessary for normal development of OB neurons and synapses.
Low molecular weight agents support survival of cultured neurons from the central nervous system
Authors: Varon S , Skaper SD , Barbin G , Selak I , Manthorpe M
Published: March 2018

Microcultures of dissociated neurons from various central and peripheral neural tissues were used for quantitative analysis and characterization of trophic agents directed to these test neurons. Media conditioned by a variety of central and peripheral glial as well as muscle cell cultures contain trophic activities for central neurons which are distinct from the more traditional protein factors directed to peripheral neurons, by at least two features: (1) they reside with low molecular weight (Mr less than 1000) agents which are resistant to heat, extremes of pH, and various proteolytic and peptidolytic enzymes; and (2) they are necessary for the short-term survival of a variety of rodent and avian central neurons, but they fail by themselves to support survival of peripheral neurons under the same culture conditions.
Optical measurements of potential changes in axons and processes of neurons of a barnacle ganglion
Authors: Ross WN , Krauthamer V
Published: March 2018

Optical techniques using voltage-sensitive dyes were used to record electrical events simultaneously from many positions on certain neurons of the barnacle supraesophageal ganglion. By signal-averaging, recordings with good signal-to-noise ratios and time resolution were obtained from fine dendritic processes as well as the axon and cell body. Controls established that the optical signals faithfully matched recordings made with intracellular electrodes for short times (5 to 10 msec), but deviations were observed at longer times. Pharmacological effects and photodynamic damage due to the dye were insignificant. The optical records were correlated with positions on the stimulated cell determined from Lucifer Yellow injections. This comparison demonstrated that signal-averaged records with large signal-to-noise ratios were obtained from those parts of the visual field which contained elements of the stimulated cell and hence could be attributed to specific locations on the cell. The quality of the optical signals were adequate to: (a) determine variations in the shape of action potentials in different parts of the cell; (b) demonstrate electrotonic spread of hyperpolarizing pulses; (c) determine the direction and velocity of action potential propagation, and (d) in some circumstances, using reasonable assumptions, estimate variations in the amplitude of action potentials or electrotonic pulses in different regions of the cell.
Locus ceruleus lesion by local 6-hydroxydopamine infusion causes marked and specific destruction of noradrenergic neurons, long-term depletion of norepinephrine and the enzymes that synthesize it, and enhanced dopaminergic mechanisms in the ipsilateral cerebral cortex
Authors: Harik SI
Published: March 2018

The local stereotaxic microinfusion of 5 micrograms of 6- hydroxydopamine in the region of the nucleus locus ceruleus causes severe loss of noradrenergic neurons with little evidence of nonspecific tissue reaction or destruction that could be detected by conventional light microscopic methods. Such lesion is accompanied by a marked and long-term depletion of norepinephrine and comparable loss of activity of its synthesizing enzymes, dopamine beta-hydroxylase and tyrosine hydroxylase, in the ipsilateral cerebral cortex. Locus ceruleus lesion was also found to increase tissue levels of dopamine and its metabolites, 3,4-dihydroxyphenylacetic acid and homovanillic acid, in the ipsilateral cortex. These results add further evidence to support the hypothesis that enhanced dopaminergic mechanisms may play a central role in compensating for chronic cortical noradrenergic denervation.
Effects of iontophoretically released peptides on primate spinothalamic tract cells
Authors: Willcockson WS , Chung JM , Hori Y , Lee KH , Willis WD
Published: March 2018

The peptides substance P (SP), methionine-enkephalin (M-ENK), leucine- enkephalin (L-ENK), and cholecystokinin (CCK) were released iontophoretically near spinothalamic tract (STT) cells in anesthetized monkeys and STT-like cells in decorticate, spinalized monkeys. Peptide effects were observed on background discharges, firing induced by release of glutamate, and activity evoked by pinching the skin. SP could have any of several actions on STT cells, including excitation, inhibition, or biphasic effects. Multiple effects often resulted while recording from an individual cell when the dose or the electrode position was changed. M-ENK and L-ENK generally inhibited STT cells, and in some cases it was possible to demonstrate a reversal of the inhibition by naloxone. CCK also caused an inhibition that was additive with that produced by L-ENK. The multiple actions of SP on STT cells suggests the possibility that there may be more than one type of SP receptor on STT cells, although alternative explanations should be considered. Inhibition of STT cells by M- and L-ENK is consistent with the known analgesic action of opiates through spinal cord mechanisms. CCK has an action on STT cells similar to that of the enkephalins.
An in vitro model of ischemia: metabolic and electrical alterations in the hippocampal slice
Authors: Whittingham TS , Lust WD , Passonneau JV
Published: March 2018

The transverse guinea pig hippocampal slice preparation was used to model the metabolic changes which occur in vivo during ischemia and recovery. Perfusing brain slices with medium devoid of glucose and oxygen elicits rapid decreases in phosphocreatine, ATP, intracellular pH, and in the evoked field potential recorded in the dentate gyrus. AMP and creatine rise during this period, while ADP and lactate levels remain unchanged. Cyclic AMP exhibits a transient increase in concentration. With the exception of ADP and lactate, these responses are very similar to those observed during in vivo ischemia. The return of glucose and oxygen to the incubation medium reverses these metabolic and electrophysiological effects and also leads to pronounced elevations in cyclic nucleotide concentrations. Metabolite concentrations approach, but do not reach, in vitro steady state levels during the first 30 min of recovery. Total adenylate and creatine steady state levels are approximately 50% of in vivo concentrations. The results suggest that, although hippocampal slices differ metabolically from in vivo tissue, they exhibit a similar pattern of metabolic responses to ischemic and reflow conditions.
Somatostatin pretreatment desensitizes somatostatin receptors linked to adenylate cyclase and facilitates the stimulation of cyclic adenosine 3':5'-monophosphate accumulation in anterior pituitary tumor cells
Authors: Reisine TD , Takahashi JS
Published: March 2018

Somatostatin-14 (SRIF) inhibits both hormone- and forskolin-stimulated cyclic adenosine 3′:5′-monophosphate (cyclic AMP) formation in tumor cells of the mouse anterior pituitary (AtT-20/D16–16). However, long- term pretreatment of cells with SRIF modifies the responsiveness of this system in two ways: The response of adenylate cyclase to stimulatory agents is enhanced, whereas the ability of SRIF to inhibit stimulated cyclic AMP formation is reduced. The supersensitive adenylate cyclase response and the SRIF desensitization were dependent on the concentration and duration of SRIF pretreatment. Enhancement of forskolin-stimulated cyclic AMP formation occurred within 4 hr, whereas that of corticotropin-releasing-factor-, (-)-isoproterenol-, and vasoactive intestinal peptide-induced cyclic AMP accumulation required 16 hr of pretreatment. The elevated responses to each of these stimulants were due to increases in their maximal ability to stimulate cyclic AMP formation. Cycloheximide treatment blocked the enhanced cyclic AMP response induced by SRIF pretreatment, suggesting a requirement for protein synthesis. In membrane preparations, SRIF pretreatment facilitated activation of adenylate cyclase by forskolin, sodium fluoride, and guanosine 5′-(beta,tau-imido)-triphosphate without affecting basal activity. These results suggest that desensitization of an inhibitory input to adenylate cyclase is accompanied by a supersensitivity of adenylate cyclase to stimulatory agents through a process requiring protein synthesis.
The D1.1 antigen: a cell surface marker for germinal cells of the central nervous system
Authors: Levine JM , Beasley L , Stallcup WB
Published: March 2018

A monoclonal antibody against a cell surface ganglioside present on neuroepithelial cells was produced by immunizing mice with the B49 cell line, a clonal line with properties of both neurons and glial cells. The expression of this antigen, designated as D1.1, was analyzed in the developing rat cerebellum. The D1.1 antigen was localized by the immunofluorescent staining method to germinal cells of the external granule layer (EGL). Fluorescent labeling of cells comprising the EGL was apparent on embryonic day 18 when the EGL first forms, and the labeling was present throughout the period of postnatal cerebellar development. No cells within the adult cerebellum were labeled with the anti-D1.1 antibody. The D1.1-labeled cells of the EGL synthesize DNA, as demonstrated by [3H] thymidine autoradiography. However, within 48 hr after their final mitosis, nascent cerebellar cells that had migrated away from the external granule layer were no longer labeled with antibody. Some of the neurons and some of the astrocytes in cerebellar cell cultures were fluorescently labeled with the anti-D1.1 antibody. The number of anti-D1.1-labeled neurons in the cultures decreased over the first 10 days in vitro in agreement with the findings that in vivo the fluorescent labeling of the D1.1 antigen disappears from postmitotic cells. The antibody recognizes a ganglioside that in thin layer chromatographic experiments has a mobility between that of the GM1 and GM2 ganglioside. These data suggest that the D1.1 ganglioside antigen is a cell surface marker for germinal cells and that the acquisition and subsequent loss of this antigen is an aspect of the biochemical maturation of neurons and glial cells.
Development of hyperpolarizing inhibitory postsynaptic potentials and hyperpolarizing response to gamma-aminobutyric acid in rabbit hippocampus studied in vitro
Authors: Mueller AL , Taube JS , Schwartzkroin PA
Published: March 2018

The postnatal development of IPSPs and response to locally applied GABA were examined using intracellular recording techniques in region CA1 of rabbit hippocampal slices maintained in vitro. Pyramidal neurons in slices from mature rabbits demonstrated an EPSP-IPSP sequence following stimulation of stratum radiatum. In these same slices, pressure application of GABA into stratum pyramidale and stratum radiatum produced membrane hyperpolarization and depolarization, respectively. Pyramidal neurons in slices from immature rabbits (age 6 to 10 days) responded differently. Stimulation of stratum radiatum produced a prolonged depolarizing postsynaptic potential; few IPSPs were observed. Ejection of GABA into either stratum pyramidale or stratum radiatum evoked a depolarizing response. The GABA agonist, 4,5,6,7- tetrahydroisoxazolo [5,4-c] pyridine-3-ol (THIP), which has been reported to activate “hyperpolarizing” GABA receptors selectively, primarily produced membrane hyperpolarization when applied to the somata of mature neurons, but it evoked a depolarization when applied to immature neurons. Bicuculline, a GABA antagonist which may have a preferential selectivity for “depolarizing” GABA receptors, was somewhat more efficacious (at 50 microM concentration) at antagonizing GABA-evoked depolarization in immature cells than GABA-evoked hyperpolarization in mature cells. This same concentration of bicuculline partially antagonized IPSPs in mature cells, and it markedly potentiated depolarizing PSPs in immature cells. Taken together, these results suggest that the late development of synaptic inhibition in rabbit hippocampus is due, at least in part, to an immaturity in the GABAergic system.
Hypothalamic neurons responding to hemodynamic input and to stimulation in the pons may influence adrenocorticotropin release
Authors: Carlson DE , Dornhorst A , Maran JW , Gann DS
Published: March 2018

Experiments were designed to identify hemodynamically sensitive neurons in the mediodorsal hypothalamus and to determine if they were also sensitive to electrical stimulation of areas in the dorsal rostral pons that were implicated previously in the control of adrenocorticotropin (ACTH) release. Cats were anesthetized with chloralose and urethane, immobilized with gallamine, and artificially respired. Hemodynamic stimuli included constriction (CC) of the supradiaphragmatic inferior vena cava to reduce venous return and sinusoidal volume pulsation (RA) of the right atrium (1 ml peak at 1 Hz). Previously, CC was shown to facilitate and RA was shown to inhibit ACTH release. Electrical stimulation in the pons consisted of single shocks (500 microA DC, 0.05 msec, negative-to-tip) delivered on each of an array of three or four bipolar co-axial electrodes in the pons. Twenty-three neurons were tested with only RA. Of these, two were inhibited, two were facilitated, and 19 did not respond. Thirty-two neurons were tested with CC. Of these, nine were inhibited, nine were facilitated, and 14 did not respond. Seventeen neurons that responded either to RA or to CC were tested with stimulation in the pons. Of these, three were orthodromically activated and two were inhibited from a total of eight pontine sites. Six of the eight sites were within 300 microns of an area shown previously to contain neurons that responded to CC. Of 31 additional sites that were stimulated, but at which stimulation did not drive neurons that responded to hemodynamic stimuli, 26 were located more than 300 microns from this area (p less than 0.01, X2 test). The data suggest that some hypothalamic neurons involved in the hemodynamic control of ACTH release receive a projection from or through the dorsal raphe nucleus medially, and the ventral locus ceruleus, locus subceruleus, and underlying reticular formation laterally. However, other neurons may receive projections that bypass these regions.
Thermodynamic parameters of end-plate channel blockade
Authors: McLarnon JG , Quastel DM
Published: March 2018

The reaction kinetics for drug blockade of postsynaptic channels at the mouse neuromuscular junction were studied. The activation energies associated with the onward and off-rate constants, from a sequential model, were measured for procaine, scopolamine, octanol, and heptanol, and from these the transition state thermodynamic parameters of free energy (delta G++), enthalpy (delta H++), and entropy (delta S++) of activation were determined. All agents showed positive entropies of activation for the channel blocking rate constant kappa 2, with the values for the alcohols significantly greater than those for the two positively charged local anesthetics. No significant differences in the activation energies for the off-rate constant kappa-2 were observed between any of the agents. The magnitude of kappa-2 decreased as the hydrophobicity of the agent increased. The large activation energies measured for kappa 2 and kappa-2 (in excess of 10 kcal/mol) are higher than expected for simple rate-limiting diffusion, and the possibility exists that channel blockade involves conformational changes in a protein segment, induced by a hydrophobic interaction between agent and intrachannel site or sites. The large entropy increase observed in the blocking step is indicative of the agent replacing structured waters of hydration near a hydrophobic region of a protein.
A critical period for the recovery of sound localization accuracy following monaural occlusion in the barn owl
Authors: Knudsen EI , Knudsen PF , Esterly SD
Published: March 2018

We studied the ability of barn owls to recover accurate sound localization after being raised with one ear occluded. Most of the owls had ear plugs inserted before they reached adult size, and therefore they never experienced normal adult localization cues until their ear plugs were removed. Upon removal of their ear plugs, these owls exhibited large systematic sound localization errors. The rate at which they recovered accurate localization decreased with the age of the bird at the time of plug removal, and recovery essentially ceased when owls reached 38 to 42 weeks of age. We interpret this age as the end of a critical period for the consolidation of associations between auditory cues and locations in space. Owls that had experienced adult localization cues for a short period of time before ear plugging recovered normal accuracy rapidly, even if they remained plugged well past the end of the critical period. This suggests that a brief exposure to normal adult cues early in the critical period is sufficient to enable the recovery of localization accuracy much later in life.
Architecture and physiology of insect cerebral neurosecretory cells
Authors: Carrow GM , Calabrese RL , Williams CM
Published: March 2018

The architecture of neurosecretory cells (NSCs) from each of two bilaterally symmetrical clusters of somata in the brain of the moth, Manduca sexta, was determined by intracellular injection of Lucifer Yellow and horseradish peroxidase. Furthermore, the ionic basis of the action potential in these cells was examined. NSC somata were visualized in the desheathed pupal protocerebrum by their reflective opalescence under direct fiberoptic illumination. Intracellular staining revealed at least six morphological classes of monopolar neurons distinguishable by the size and position of their somata as well as the patterns of their dendritic fields, axonal pathways, and terminal projections. The number of morphological classes of NSCs is in accord with the estimated number of brain neurohormones--a finding that suggests a different neuroendocrine function for each class. The observed overlap of dendritic fields is consistent with synaptic interaction among NSCs or the sharing of common inputs. Finally, the demonstration of terminal ramifications and varicosities in the corpora cardiaca and corpora allata confirms that these are the neurohemal organs for cerebral NSCs. Intracellular recordings revealed that the NSC somata had resting membrane potentials of 35 to 45 mV and were electrically excitable; they showed broad (10 to 20 msec) overshooting action potentials, long hyperpolarizing afterpotentials, and postsynaptic potentials. Impulse amplitude was maintained in the absence of external sodium or in the presence of 10(-5)M tetrodotoxin, but impulses were completely and reversibly blocked by 10 mM cobalt. Postsynaptic potentials were blocked by all three conditions. These results indicate that impulses in the somata are generated primarily by calcium inward currents. Cations, tetrodotoxin, and horseradish peroxidase in the bathing medium did not readily exchange with the extracellular space of the desheathed brain. However, light protease treatment of the brain facilitated ion exchange. These findings provide evidence for the persistence of a blood-brain barrier even in desheathed ganglia.
Preserved learning in monkeys with medial temporal lesions: sparing of motor and cognitive skills
Authors: Zola-Morgan S , Squire LR
Published: March 2018

In an effort to bring into correspondence the findings from human amnesic patients and the findings from monkeys with surgical lesions of those brain regions thought to be affected in the human cases, we have addressed in three experiments the implication of findings that human amnesia spares motor and cognitive skills. In the first experiment, monkeys with conjoint lesions of hippocampus and amygdala (H-A), which reproduced the surgical removal sustained by the noted amnesic case H.M., were only mildly impaired in learning relatively difficult pattern discrimination tasks. Monkeys with lesions of temporal stem matter (TS) were severely impaired on the same tasks, due to an apparent deficiency in visual information processing. In the second experiment, monkeys with H-A lesions were severely impaired at learning relatively easy discrimination tasks that could be acquired rapidly by normal monkeys. Monkeys with TS lesions were not impaired. In the third experiment, monkeys with H-A lesions exhibited normal acquisition of two motor skill tasks. These data can be understood in the light of a distinction between kinds of memory, founded in recent studies of the neuropsychology of human amnesia. These studies have led to a distinction between the learning of skills or procedures, which is spared in human amnesia, and the learning of facts and episodes, which is impaired. Monkeys with H-A lesions are normal at skill learning like human amnesic patients with similar lesions. This conclusion depends in part on the argument developed here that pattern discrimination learning, as accomplished by monkeys, has a large skill-like component. These results bring into correspondence the behavioral data from human amnesic patients and operated monkeys and set the stage for identifying precisely what brain structures must be damaged to produce amnesia.