Experimental Brain Research

Seress, L.; Frotscher, M.; Ribak, C.

doi: 10.1007/BF00230680pmid: 2591505

221 78 78 1 1 L. Seress M. Frotscher C. E. Ribak Institute of Anatomy, Johann Wolfgang Goethe University Theodor-Stern-Kai 7 D-6000 Frankfurt 70 Federal Republic of Germany Department of Anatomy and Neurobiology University of California 92717 Irvine CA USA Summary Glutamate decarboxylase (GAD)-positive and Golgi impregnated local circuit neurons of the hippocampal formation of five day old rats were examined in light and electron microscopic preparations. The ultrastructural features of these neurons were similar in both the dentate gyrus and CA1 area of Ammon's horn. Somata displayed a perikaryal cytoplasm rich in organelles but lacked organized Nissl bodies. Most nuclei showed intranuclear infoldings of varying degrees but no intranuclear sheets or rods were found. Somata and dendrites were contacted by relatively immature axon terminals that formed mainly symmetric synapses. The axons of local circuit neurons in both the dentate gyrus and Ammon's horn formed symmetric synapses with somata and dendrites of the principal neurons in these regions. Thus, both GAD-positive and Golgi-impregnated terminals of local circuit neurons were observed to form synapses with pyramidal and granule cells. These terminals were usually small and contained relatively few pleomorphic synaptic vesicles. The results show that a circuitry for inhibition is established in the 5 day old dentate gyrus and Ammon's horn, even though the local circuit neurons lack some of the typical adult ultrastructural features at this age.

Forget, R.; Pantieri, R.; Pierrot-Deseilligny, E.; Shindo, M.; Tanaka, R.

doi: 10.1007/BF00230681pmid: 2591506

221 78 78 1 1 R. Forget R. Pantieri E. Pierrot-Deseilligny M. Shindo R. Tanaka Clinical Neurophysiology, Rééducation Hôpital de la Salpêtrière F-75651 13 Paris Cedex France Université de Montréal, Faculté de Médecine, Ecole de Réadaptation Montréal Quebec Canada Clinica Neurologica dell'Universitá Bologna Italy Department of Medicine (Neurology) Shinshu University Matsumoto Japan Tokyo Metropolitan Institute for Neurosciences Tokyo Japan Summary The neuronal pathway of the facilitation of quadriceps (Q) motoneurones (MNs) evoked by stimulation of the common peroneal nerve (CPN) has been reinvestigated using both the post-stimulus time histogram (PSTH) method for measurement of the firing probability of individual units and the H reflex technique. It has been found that Ia (and to an unknown extent Ib) afferents from pretibial flexors — but not from peroneal muscles — are responsible for this excitation. The central latency of the CPN-induced excitation of Q MNs was estimated to be 3–3.7 ms longer than that of their monosynaptic Ia excitation. To further investigate the neuronal pathway of the CPN-induced excitation the spatial facilitation technique was used, the effects on the Q H reflex of two conditioning stimuli (applied to the CPN and the femoral nerve — FN) being compared when applied separately and together. When the two conditioning volleys were timed to reach the spinal cord simultaneously the facilitation of the H reflex on combined stimulation was larger than the algebraic sum of the effects by separate stimuli in 40% of the cases. It is argued that this additional facilitation reflects summation at a premotoneuronal level and it is concluded that non-monosynaptic Ia excitation of Q MNs from Q and pretibial flexors is, at least partly, mediated through a common pathway. In those individual units in which stimulation of the FN and/or the CPN evoked a non-monosynaptic Ia excitation, this excitation was reduced on combined stimulation of the two nerves. It is argued that this reflects inhibition of the interneurones mediating the excitation, i.e. consists in a disfacilitation of the MNs. It is suggested that the non-monosynaptic (homonymous and heteronymous) Ia excitation of Q MNs in man (and the inhibition of this excitation) is mediated through a system of neurones similar to the system recently described in the cat by Edgley and Jankowska (1987).

Forget, R.; Hultborn, H.; Meunier, S.; Pantieri, R.; Pierrot-Deseilligny, E.

doi: 10.1007/BF00230682pmid: 2591514

221 78 78 1 1 R. Forget H. Hultborn S. Meunier R. Pantieri E. Pierrot-Deseilligny Clinical Neurophysiology, Rééducation, Hôpital de la Salpêtrière F-75651 13 Paris Cedex France Université de Montréal, Faculté de Médecine, Ecole de Réadaptation Montréal Quebec Canada Department of Neurophysiology The Panum Institute, University of Copenhagen Copenhagen Denmark Clinica Neurologica dell' Università Bologna Italy Summary The facilitation of the quadriceps (Q) H reflex evoked by stimulation of group I afferents from pretibial flexors exhibits biphasic changes during Q voluntary contraction. At short conditioning-test intervals the facilitation is increased, whereas it is decreased at longer intervals and/or at high conditioning stimulus intensities and/or when the contraction strength is increased. The spatial facilitation at a premotoneuronal level observed at rest on combined stimulation — common peroneal nerve (CPN) and femoral nerve (FN) — regularly disappeared during contraction. It is argued that the increase in facilitation at the onset of the weakest Q contraction reflects a descending facilitation of the interneurones mediating the CPN-induced excitation to Q MNs. An occlusion of descending and peripheral excitation in these interneurones can easily account for the depression of the facilitation when the conditioning stimulus intensity and/or the strength of the contraction is increased. However, occlusion cannot explain all the results and inhibition of the neurones mediating excitation of MNs, i.e. disfacilitation of the MNs, probably contributes to the decrease in facilitation observed during contraction.

Crone, C.; Nielsen, J.

doi: 10.1007/BF00230683pmid: 2591515

221 78 78 1 1 C. Crone J. Nielsen Department of Neurophysiology The Panum Institute, University of Copenhagen Blegdamsvej 3C DK-2200 Copenhagen N Denmark Department of Clinical Neurophysiology Rigshospitalet Blegdamsvej 9 DK-2100 Copenhagen Ø Denmark Summary A long lasting inhibition (> 8 s) of the soleus Hoffmann reflex (H-reflex) was evoked by a preceding soleus H-reflex, by a brief voluntary ankle flexor or extensor muscle contraction or by a tap applied to the Achilles tendon. The time course of this long lasting inhibition was similar in all these cases, suggesting that the same spinal mechanism is involved. Furthermore, it was shown that the post-activation depression may interfere with the determination of inhibitory or facilitatory effects on the H-reflex. It is stressed that when the onset of inhibitory or facilitatory effects on the soleus H-reflex is to be determined in relation to start of an ankle movement, either very long stimulus intervals (> 8 s) must be used, or the onset must be determined in relation to a reference value of the soleus H-reflex, which may be influenced by the long lasting inhibitory effect, but not yet by the succeeding muscle contraction.

Ceccatelli, S.; Cintra, A.; Hökfelt, T.; Fuxe, K.; Wikström, A.; Gustafsson, J.

doi: 10.1007/BF00230684pmid: 2591516

221 78 78 1 1 S. Ceccatelli A. Cintra T. Hökfelt K. Fuxe A. -C. Wikström J. Å. Gustafsson Department of Histology and Neurobiology Karolinska Institute P.O. Box 60400 S-104 01 Stockholm Sweden Department of Medical Nutrition Huddinge Hospital S-104 01 Stockholm Sweden Summary The paraventricular nucleus (PVN) of male albino rats was analyzed for the presence of glucocorticoid receptor-like immunoreactivity (GR-LI) in neuropeptide containing neurons. Using immunohistochemistry, coronal sections trough the entire PVN were double-stained with a mouse monoclonal antibody against GR and one of the following antisera: rabbit antiserum to corticotropin releasing factor (CRF), neurotensin (NT), enkephalin (ENK), cholecystokinin (CCK), thyrotropin releasing hormone (TRH), galanin (GAL), peptide histidine isoleucine (PHI), vasoactive intestinal polypeptide (VIP), somatostatin (SOM) or tyrosine hydroxylase (TH). For comparison the occurrence of GR-LI in NT-, SOM-, NPY- or TH-positive neurons of the arcuate nucleus was also studied. Our results indicate that GR-LI is present in the parvocellular part of the PVN but not in its magnocellular portion. Virtually every parvocellular neuron in the PVN containing one of the above mentioned peptides was also positive for GR, with the exception of SOM neurons, of which only about two thirds showed detectable levels of GR-LI. All TH-positive, presumably dopamine neurons in the PVN were GR-positive. In the arcuate nucleus all TH- and NPY-positive neurons as well as a large proportion of the SOM- and NT-immunoreactive neurons contained GR-LI. The results indicate that in the PVN, in addition to the CRF neurons, certain peptidergic neurons in the parvocellular part of the PVN, without any established role in the control of ACTH synthesis and release, may also be under glucocorticoid control. This seems to be the case also for most arcuate neurons.

Kosaka, T.; Heizmann, C.; Barnstable, C.

doi: 10.1007/BF00230685pmid: 2591517

221 78 78 1 1 T. Kosaka C. W. Heizmann C. J. Barnstable National Institute for Physiological Sciences Myodaiji 444 Okazaki Japan Department of Pediatrics, Division of Clinical Chemistry University of Zürich Steinwiesstraße 75 CH-8032 Zürich Switzerland Department of Ophthalmology and Visual Science and Section of Neuroanatomy Yale University School of Medicine 06510 New Haven CT USA Department of Anatomy, Faculty of Medicine Kushu University Higashi-ku 812 Fukuoka Japan Summary Monoclonal antibody VC1.1 is shown to stain selectively a subpopulation of GABAergic neurons in the rat cerebral cortex. Almost all VC1.1 immunoreactive cells were also GABA-like immunoreactive (GABA-LI) and parvalbumin (PV) immunoreactive, whereas they were about 30% and 65% of GABA-LI and PV-positive cells in the parietal cortex and about 13% and 32% in the occipital cortex, respectively. Although a few VC1.1 positive cells showed somatostatinlike and/or cholecystokinin-like immunoreactivities, they were exceptional (less than 1% of VC1.1 positive cells). Furthermore about 90% of VC1.1 positive cells were also stained with a lectin, Vicia villosa agglutinin, with a specific affinity for terminal N-acetylgalactosamine.

Romaiguère, P.; Vedel, J.; Pagni, S.; Zenatti, A.

doi: 10.1007/BF00230686pmid: 2591518

221 78 78 1 1 P. Romaiguère J. -P. Vedel S. Pagni A. Zenatti Laboratoire de Neurosciences Fonctionnelles, C.N.R.S. 31, Chemin Joseph Aiguier F-13402 Marseille Cédex 9 France Summary The physiological properties of 355 motor units (MUs) recorded in the extensor carpi radialis muscles were studied in 34 healthy human subjects during isometric contractions. MU selective twitches were educed from the whole muscle force using the spike-triggered averaging method. The twitch contraction times and twitch forces were measured. From these data it was attempted to estimate the distribution of fast and slow MUs in the muscles studied. MU recruitment thresholds were systematically measured during stereotyped slow ramp contractions (force increase=0.25 N·s -1 ). Degrees of correlation between contraction times, twitch forces and recruitment thresholds were pair analysed by computing simple regression curves and correlation coefficients. The degrees of correlation were compared between 245 MUs recorded in 34 subjects and 66 MUs recorded in a single subject. Analysis of the instantaneous discharge frequency of 132 MUs showed the existence of a remarkable degree of correlation (correlation coefficient, r =-0.75) between the “frequency rise times” (discharge onset to maximal frequency) and the MU twitch contraction times; i.e., the “frequency rise times” increase when the twitch contraction times decrease. The possibility that muscle contraction may be differentially modulated on the basis of this discharge property of the MUs is discussed. The results are compared to previous data and the limitations of the spike-triggered averaging method applied to long muscles in man are extensively discussed.

John, K.; Goodwin, A.; Darian-Smith, I.

doi: 10.1007/BF00230687pmid: 2591519

221 78 78 1 1 K. T. John A. W. Goodwin I. Darian-Smith Department of Anatomy University of Melbourne Grattan Street 3052 Parkville Victoria Australia Summary The ability of human subjects to discriminate plane metal plates of different thickness was measured using a forced-choice paradigm. The plates, made by electroplating a thin layer of copper onto flat brass shims, were gripped between the thumb and the index finger. Subjects were presented with either 2 standard plates (0.2 mm thick), or a standard plate and a test plate that was slightly thicker, and were required to state which alternative had occurred. When the edges of the plates could not be touched, a difference in thickness of about 0.075 mm could be discriminated. Surprisingly, when the edges were included in the grip, performance did not improve. All hypotheses of strategies used by the subjects required them to sense the angles of the finger joints with a precision of about 0.1°.

Doudet, D.; Miyake, H.; Finn, R.; McLellan, C.; Aigner, T.; Wan, R.; Adams, H.; Cohen, R.

doi: 10.1007/BF00230688pmid: 2512179

221 78 78 1 1 D. J. Doudet H. Miyake R. T. Finn C. A. McLellan T. G. Aigner R. Q. Wan H. R. Adams R. M. Cohen Section on Clinical Brain Imaging LCM, NIMH Bldg. 10/4N317 20892-1000 9000 Rockville Pike, Bethesda MD USA Radiopharmaceutical Chemistry NMD, CC 9000 Rockville Pike 20892-1000 Bethesda MD USA Laboratory of Neuropsychology, NIMH, NIH 9000 Rockville Pike 20892-1000 Bethesda MD USA Summary Positron emission tomography following intravenous administration of 6-( 18 F)-L-fluorodopa was used to investigate the usefulness of PET for the assessment of normal and abnormal dopaminergic function. For this purpose, the incracerebral distribution of 6-( 18 F)-L-fluorodopa and its metabolites was evaluated in normal control and asymptomatic MPTP-treated rhesus monkeys. MPTP is a neurotoxic compound which destroys selectively the dopaminergic neurons of the nigrostriatal pathways in primates. The 18 F accumulation was found to be significantly reduced in the striatum, putamen more than caudate, of the MPTP-treated animals compared to the normal controls. The 18 F accumulation in dopamine-poor areas did not differ between the two groups. The ratios of striatum to dopamine-poor brain area were highly correlated to the concentrations of the dopamine metabolite, homovanillic acid, in the cerebrospinal fluid of the same animals. The findings are consistent with the hypothesis that “silent damage” to the dopaminergic nigral neurons may precede the onset of parkinsonism by many years and that PET scanner examination using 6-( 18 F)-L-fluorodopa may be useful in the detection of subtle dopaminergic dysfunctions as may exist in DA-related motor syndromes and neuropsychiatric disorders.

Luijtelaar, M.; Steinbusch, H.; Tonnaer, J.

doi: 10.1007/BF00230689pmid: 2591520

221 78 78 1 1 M. G. P. A. van Luijtelaar H. W. M. Steinbusch J. A. D. M. Tonnaer Department of Pharmacology Free University van der Boechorststraat 7 NL-1081 Amsterdam BT The Netherlands Department of CNS Pharmacology Organon Int. Oss BV The Netherlands Summary Recent morphological observations have suggested neurotransmitter specific degeneration of amongst others, the serotonergic system in the aged rat brain. However, morphological studies can only give a static picture of the events that take place over a period of several months. In the present study we used an experimental model in which degeneration of the serotonergic system in the young adult rat brain was produced on a short time scale. Morphological changes were studied 2 h and 1 or 14 days after intracerebroventricular injection of 5,7-dihydroxytryptamine (5,7-DHT). Nonspecific damage and severe depletion of serotonergic fibers was observed in the immediate surroundings of the injection site, representing the effects of high local concentrations of 5,7-DHT. Sometime after injection swollen varicosities and dilated non-varicose fibers were observed. Fourteen days after the 5,7-DHT treatment cluster-like fibers appeared. It is argued that these swollen and crumpled fiber knots are slowly degenerating fibers. A comparison is made with the abnormal serotonergic fibers in the aged rat brain and it is concluded that these aged abnormal fibers represent axonal degeneration of the serotonergic system in the senescent rat brain.