| 1. |
- Garwicz, Martin, et al.
(författare)
-
Functional organization of the intermediate cerebellum.
- 1995
-
Ingår i: Alpha and Gamma Motor Systems. - Boston, MA : Springer US. - 9780306451867 - 9781461519355 ; , s. 399-402
-
Konferensbidrag (refereegranskat)abstract
- The uniform organisation of the neuronal circuitry throughout the cerebellar cortex suggests a uniform mode of operation and thus emphasises the importance of local afferent and efferent connections in determining the function of a particular part of the cortex. Based on the organisation of these connections the cerebellar cortex of the cat is divided into about ten sagittally oriented zones (see Ito, 1984 for references). A zone is anatomically defined by its projection to a restricted part of the intracerebellar or vestibular nuclei and its climbing fibre input from a circumscribed part of the inferior olive. Some of the zones are functionally coupled in that they receive branching collaterals from common olivary neurones and in turn project to the same subdivision of the intracerebellar nuclei. Since each part of the inferior olive receives input from a specific set of spino-olivary pathways, the zones can be electrophysiologically identified by the latencies and receptive fields of climbing fibre responses evoked on peripheral stimulation. The organisation of olivary afferent and nuclear efferent connections suggests that each zone, or in some cases an ensemble of zones, controls specific motor systems.
|
|
| 2. |
- Gladden, M H, et al.
(författare)
-
Coupling between serotoninergic and noradrenergic neurones and gamma-motoneurones in the cat.
- 2000
-
Ingår i: The Journal of physiology. - 0022-3751. ; 527 Pt 2, s. 213-23
-
Tidskriftsartikel (refereegranskat)abstract
- Noradrenaline is known to suppress transmission from group II muscle afferents when locally applied to gamma-motoneurones, and serotonin (5-HT) facilitates the transmission. The purpose of this investigation was to search for evidence of monoaminergic innervation of gamma-motoneurones. Eight gamma-motoneurones were labelled with rhodamine-dextran, and 50 micrometer thick sagittal sections of the spinal cord containing them were exposed to antibodies against dopamine beta-hydroxylase (DBH) and 5-HT. All the cells were directly and/or indirectly excited by muscle group II afferents from the muscle they innervated and/or other muscles. Appositions between monoaminergic fibres and the labelled somata and dendrites were located with three-colour confocal laser scanning microscopy by examining series of optical sections at 1 or 0.5 micrometer intervals. DBH and 5-HT varicosities formed appositions with the somata and dendrites of all the gamma-motoneurones. The mean packing densities for 5-HT (1.12 +/- 0.11 appositions per 100 micrometer(2) for somata and 0.91 +/- 0.07 per 100 micrometer(2) for dendrites) were similar to the densities of contacts reported for alpha-motoneurones. Monoaminergic varicosities in apposition to dendrites greatly outnumbered those on the somata. The density of DBH appositions was consistently lower - corresponding means were 53% and 62% of those for 5-HT on the somata and dendrites, respectively. It is concluded from an analysis of the distribution and density of varicosities in apposition to the gamma-motoneurones compared with the density in the immediate surround of the dendrites that there is indeed both a serotoninergic and noradrenergic innervation of gamma-motoneurones.
|
|
| 3. |
- Gladden, M. H., et al.
(författare)
-
Coupling between serotoninergic and noradrenergic neurones and γ-motoneurones in the cat
- 2000
-
Ingår i: Journal of Physiology. - : Wiley. - 0022-3751 .- 1469-7793. ; 527, s. 213-223
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Noradrenaline is known to suppress transmission from group II muscle afferents when locally applied to γ-motoneurones, and serotonin (5-HT) facilitates the transmission. The purpose of this investigation was to search for evidence of monoaminergic innervation of γ-motoneurones. 2. Eight γ-motoneurones were labelled with rhodamine-dextran, and 50 μm thick sagittal sections of the spinal cord containing them were exposed to antibodies against dopamine β-hydroxylase (DBH) and 5-HT. All the cells were directly and/or indirectly excited by muscle group II afferents from the muscle they innervated and/or other muscles. 3. Appositions between monoaminergic fibres and the labelled somata and dendrites were located with three-colour confocal laser scanning microscopy by examining series of optical sections at 1 or 0·5 μm intervals. 4. DBH and 5-HT varicosities formed appositions with the somata and dendrites of all the γ-motoneurones. The mean packing densities for 5-HT (1·12 ± 0·11 appositions per 100 μm2 for somata and 0·91 ± 0·07 per 100 μm2 for dendrites) were similar to the densities of contacts reported for α-motoneurones. Monoaminergic varicosities in apposition to dendrites greatly outnumbered those on the somata. 5. The density of DBH appositions was consistently lower - corresponding means were 53% and 62% of those for 5-HT on the somata and dendrites, respectively. 6. It is concluded from an analysis of the distribution and density of varicosities in apposition to the γ-motoneurones compared with the density in the immediate surround of the dendrites that there is indeed both a serotoninergic and noradrenergic innervation of γ-motoneurones.
|
|
| 4. |
- Gladden, M H, et al.
(författare)
-
New observations on coupling between group II muscle afferents and feline gamma-motoneurones.
- 1998
-
Ingår i: The Journal of physiology. - 0022-3751. ; 512 ( Pt 2), s. 507-20
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Extra- or intracellular recordings were made from seventy-six gamma-motoneurones of hindlimb muscles in chloralose anaesthetized cats to re-assess the coupling between secondary muscle spindle afferents (group II muscle afferents) and these neurones. The latencies of a number of responses evoked by group II muscle afferents in gamma-motoneurones were shorter than minimal latencies of responses induced disynaptically in other spinal neurones. These latencies are therefore compatible with monosynaptic coupling between muscle spindle secondaries and gamma-motoneurones. 2. Responses fulfilling criteria for monosynaptically evoked responses were seen in about one third of gamma-motoneurones with input from the group II muscle afferents tested (in 6 of 18 motoneurones recorded intracellularly and in 26 of 74 motoneurones recorded extracellularly). They were usually evoked from only one of the stimulated nerves, stimulation of group II afferents of other nerves being followed by responses at longer latencies. 3. Most gamma-motoneurones were excited by group II afferents from several muscles, both flexors and extensors. However, a comparison of group II input to gamma-motoneurones innervating medial gastrocnemius and four other hindlimb muscles revealed differences in both incidence and sources. 4. This study extends results of previous studies by providing evidence that some synaptic actions of group II afferents, including afferents from the same muscle, are evoked monosynaptically, and may assist in sustaining the activation of gamma-motoneurones by positive feedback.
|
|
| 5. |
|
|
| 6. |
- Jankowska, Elzbieta, et al.
(författare)
-
Modulation of responses of feline gamma-motoneurones by noradrenaline, tizanidine and clonidine.
- 1998
-
Ingår i: The Journal of physiology. - 0022-3751. ; 512 ( Pt 2), s. 521-31
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Effects of noradrenaline (NA) and the alpha2 agonists tizanidine and clonidine were tested on extracellularly recorded responses of gamma-motoneurones in deeply anaesthetized cats. Two types of responses were used; firstly, short latency phasic responses evoked by electrical stimulation of group II afferents in a muscle nerve and, secondly, tonic background discharges. 2. Responses evoked by group II muscle afferents were depressed when NA and tizanidine were applied ionophoretically close to a gamma-motoneurone and when clonidine was applied systemically. The number of spike potentials evoked by stimulation of these afferents decreased and their latencies increased. Responses evoked by flexor or extensor afferents in gamma-motoneurones innervating flexors or extensors were similarly depressed. 3. Tonic discharges were inconsistently and/or insignificantly affected by locally applied NA and tizanidine but were depressed by systemically applied clonidine. 4. Control tests indicate specific effects of NA and tizanidine application since similarly ionophoresed H+ ions did not change responses of gamma-motoneurones to stimulation of group II afferents, or only weakly enhanced their background discharges. Furthermore, serotonin ejected from a solution with a similar pH facilitated rather than depressed responses of gamma-motoneurones. 5. The results indicate that some antispastic effects of clonidine and tizanidine may be due to the depression of group II-evoked responses of gamma-motoneurones, resulting in weaker responses of muscle spindles to muscle stretches.
|
|
