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- Brodin, L, et al.
(författare)
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The reticulospinal glutamate synapse in lamprey: plasticity and presynaptic variability
- 1994
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Ingår i: Journal of Neurophysiology. - 0022-3077 .- 1522-1598. ; 72, s. 592-604
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Tidskriftsartikel (refereegranskat)abstract
- 1. The glutamatergic synapses formed between the unbranched giant reticulospinal axons onto spinal neurons in lamprey offer a central vertebrate synapse in which the presynaptic element can be impaled with one or several microelectrodes, which may be used for recording as well as microinjection of different substances. To provide a basis for the use of this synapse in studies of release mechanisms, we have examined the use-dependent modulation of the synaptic response under conditions of conventional cell body stimulation, and during direct stimulation of the presynaptic axon. 2. To examine the stability of the mixed electrotonic and chemical reticulospinal excitatory postsynaptic potential (EPSP) over time, action potentials were evoked at a rate of 1 Hz for 800-1000 trials. In three out of seven synapses the chemical component remained at a similar amplitude, while in four cases a progressive decrease (up to 35%) occurred. The electrotonic component remained at a similar amplitude in all cases. 3. During paired pulse stimulation of the reticulospinal cell body (pulse interval 65 ms) the chemical EPSP component showed a net facilitation in all cases tested [from 0.64 +/- 0.35 to 0.89 +/- 0.48 (SD) mV, n = 13], while the peak amplitude of the electrotonic component was unchanged (1.37 +/- 0.68 and 1.36 +/- 0.66 mV, respectively). Recording of the axonal action potential during paired pulse stimulation showed that the width of the first and second action potential did not differ [1/2 width (2.48 +/- 0.39 ms and 2.48 +/- 0.42 ms, respectively; n = 8)]. 4. The degree of facilitation varied markedly between different synapses, ranging from an increase of a few percent to a two-fold increase (24 +/- 16% mean change of total EPSP amplitude, corresponding to 44 +/- 26% mean change of chemical EPSP amplitude). This type of variability was also observed in synapses made from the same unbranched reticulospinal axon onto different postsynaptic cells. 5. When paired pulse stimulation was applied to the reticulospinal axon in the very vicinity of the synaptic area (0.1-1 mm) a net depression of the chemical component occurred in 11 out of 19 cases, and in the remaining cases the level of net facilitation was lower as compared with cell body stimulation (range between +17 and -23% change of total EPSP amplitude; mean -5%; n = 19). 6. To test if the change of the EPSP plasticity during local stimulation correlated with an increased transmitter release, two microelectrodes were placed in the same reticulospinal axon at different distances from the synaptic area.(ABSTRACT TRUNCATED AT 400 WORDS)
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| 2. |
- Ericsson, J., et al.
(författare)
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The lamprey provides a vertebrate blueprint of the mammalian basal ganglia
- 2010
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Konferensbidrag (refereegranskat)abstract
- The basal ganglia are a group of subcortical nuclei that play a prominent role in motor function in mammals as well as in lamprey. The aim of the present study was to characterize the different components of the lamprey basal ganglia, and determine to what extent they correspond to those found in the mammalian basal ganglia. Anatomical tract tracing, immunohistochemistry and acute brain slice patch clamp recordings were employed to address this question.Two pallidal regions were identified in the lamprey; one region, considered homologous to the mammalian globus pallidus, was located ventral to the ementia thalami on the telencephalic/diencephalic border. It receives striatal input from inwardly rectifying neurons (IRNs) and contains GABAergic projection neurons, of which those projecting to the tectum were shown to be tonically active. It also contains neurons immunoreactive for parvalbumin. Separate subpopulations of pallidal neurons project to the optic tectum, the diencephalic and mesencephalic locomotor regions (MLR).Another region, in the midbrain, considered homologous to the substantia nigra pars reticulata receives input from a different subset of IRNs and sends GABAergic projections to the tectum and the diencephalic locomotor region. This midbrain region also contains parvalbumin immunoreactive neurons. The main population of striatal neurons, IRNs, displays the anatomical and electrophysiological hallmarks of mammalian medium spiny neurons, including inward rectification and ramping responses to first spike. It also contains neurons with properties similar to fast-spiking neurons. The striatum receives pallial and thalamic input as well as ascending dopaminergic, serotonergic and histaminergic inputs, similar to that in mammals.Our results suggest that the basic features of the basal ganglia with regard to both structure and function are conserved throughout the vertebrate phylogeny, including striatal/pallidal subdivisions.
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| 6. |
- Wikström, M, et al.
(författare)
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The action of 5-HT on calcium-dependent potassium channels and on the spinal locomotor network in lamprey is mediated by 5-HT1A-like receptors.
- 1995
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Ingår i: Brain Research. - 0006-8993 .- 1872-6240. ; 678, s. 191-199
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Tidskriftsartikel (refereegranskat)abstract
- 5-HT has a powerful modulatory action on the firing properties of single neurons as well as on locomotor activity. In lamprey, 5-HT increases the neuronal firing frequency in spinal neurons by reducing the conductance in Ca(2+)-dependent K+ channels (KCa) underlying the slow afterhyperpolarization (sAHP), and it also lowers the burst frequency of the spinal locomotor network. To elucidate which type of 5-HT receptor mediates these effects, different specific receptor agonists and antagonists were applied during intracellular current clamp recordings and during NMDA-induced fictive locomotion in the lamprey spinal cord in vitro preparation. The 5-HT1A receptor agonist 8-OH-DPAT ((+/-)-8-hydroxy-dipropylaminotetralin hydrobromide), the 5-HT1 receptor agonist 5-CT (5-carboxyamidotryptamine maleate) and the 5-HT2 receptor agonist alpha-CH3-5-HT (alpha-methylserotonin maleate) all reproduced the actions of 5-HT at both the cellular and the network levels. The effects of all agonists were completely or partially blocked by the 5-HT1A and 5-HT2 receptor antagonist spiperone (spiroperidol hydrochloride) while selective 5-HT2 receptor antagonists were ineffective. The selective 5-HT1A receptor antagonist S(-)-UH301 (S(-)-5-fluoro-8-hydroxy-dipropylaminotetralin hydrochloride) also counteracted the effect of 5-HT on the sAHP. 5-HT3 and 5-HT4 receptor agonists and antagonists were without effects. The intracellular coupling mechanism was not sensitive to pertussis toxin nor to the cAMP dependent protein kinase blocker (Rp)-cAMPS.(ABSTRACT TRUNCATED AT 250 WORDS)
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