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N Dusticier

Publications and source records attributed to N Dusticier.

28 records · Page 2Linked to original sources
PubMed1982

Effect of superficial radial nerve stimulation on the activity of nigro-striatal dopaminergic neurons in the cat: role of cutaneous sensory input.

The release of 3H-dopamine (DA) continuously synthesized from 3H-tyrosine was measured in the caudate nucleus (CN) and in the substantia nigra (SN) in both sides of the brain during electrical stimulation of the superficial radial nerve in cats lightly anaesthetized with halothane. Use of appropriate electrophysiologically controlled stimulation led to selective activation of low threshold afferent fibers whereas high stimulation activated all cutaneous afferents. Results showed that low threshold fiber activation induced a decreased dopaminergic activity in CN contralateral to nerve stimulation and a concomitant increase in dopaminergic activity on the ipsilateral side. Stimulation of group I and threshold stimulation of group II afferent fibers induced changes in the release of 3H-DA mainly on the contralateral CN and SN and in the ipsilateral CH. High stimulation was followed by a general increase of the neurotransmitter release in the four structures. This shows that the nigro-striatal dopaminergic neurons are mainly--if not exclusively--controlled by cutaneous sensory inputs. This control, primarily inhibitory in the side contralateral to the stimulation, seems rather non-specific when high threshold cutaneous fibers are also activated. Such activations could contribute to reestablish sufficient release of DA when the dopaminergic function is impaired as in Parkinson's disease.

Animals↗
PubMed1981

Increased glutamate decarboxylase activity in the red nucleus of the adult cat after cerebellar lesions.

Glutamate decarboxylase (GAD)activity, a marker for GABAergic structures, was studied in the cat red nucleus. GAD is more concentrated in the rostral than in the caudal third of the structure. GAD levels were measured after chronic unilateral lesions of the cerebellum. Destruction of the dentate area and of the nucleus interpositus induced increases of GAD in the contralateral but not in the ipsilateral red nucleus. Similar changes also occurred in the denervated nucleus ventralis lateralis (VL) and nucleus ventralis anterior (VA) of the thalamus. Results show that loss of the excitatory cerebellar input could lead to changes in inhibitory GABAergic nerve terminals. This increase may be induced transsynaptically within existing neurons or, more likely, additional GAD-containing nerve terminals may be formed by axonal sprouting.

Afferent Pathways↗
PubMed1981

Decrease in choline acetyltransferase and in high affinity glutamate uptake in the red nucleus of the cat after cerebellar lesions.

Acetylcholine (ACh) is suggested to be a neurotransmitter in cerebellothalamic and cerebellorubral fibres. We therefore measured choline acetyltransferase (CAT) activity in the cat red nucleus after lesion of the contralateral cerebellum. Decreased CAT activity was obtained (-37%), specifically localized in the red nucleus and particularly in its rostral parvocellular part. Since the red nucleus of the cat displays rather low CAT levels, the possible cholinergic input seems not be sufficient to explain the powerful action of the cerebellum on red nucleus magnocellular neurons. As glutamic acid (Glu) may be the neurotransmitter of many excitatory systems in the brain, we measured high affinity Glu uptake in the red nucleus after lesions of the contralateral cerebellum. Results showed a decreased (-35%) Glu activity restricted to the red nucleus and particularly in its caudal magnocellular part.

Animals↗
PubMed1981

Glutamate decarboxylase distribution in discrete motor nuclei in the cat brain.

The distribution of activity of glutamate decarboxylase (GAD), the enzyme synthesising gamma-aminobutyric acid (GABA), was measured in the cat brain by means of microdissection of the structures from frozen slices and a radioisotopic assay for the enzyme. About 20 cerebral regions were chosen for study because of their role in sensorimotor integration. GAD presented an uneven distribution among these areas. Highest activities were found in the basal ganglia, particularly in the substantia nigra and in the globus pallidus, and to a lesser extent in the cerebellum. Relatively low levels of the enzyme were found in the thalamus and in the cerebral motor cortex. Special detailed studies were made in the caudate nucleus, the substantia nigra, and in the red nucleus for the purpose of defining the intranuclear distribution of their GABAergic innervation. There were only small differences in the rostro-caudal distribution of the enzyme in the head of the caudate nucleus but GAD activity was higher in the ventral than in the dorsal part of the structure. In the substantia nigra, GAD activity was high in both the medial and intermediate thirds of the structure. The GAD activity decreased from the caudal to the rostral part of the nucleus. GAD levels were lower in the caudal part of the red nucleus than in the rostral part. These results indicate that GABA would be present as a putative neurotransmitter in many motor nuclei of the cat brain. In view of the general inhibitory action of this amino acid, this could be related to the presence of inhibitory responses widely distributed in these nuclei as identified by mean of electrophysiological studies. The origin of these GABAergic innervations in many cases remains to be determined.

Animals↗
PubMed1980

Choline acetyltransferase activity in discrete regions of the cat brain.

Choline acetyltransferase (CAT) activity was measured in the cat brain using a microdissection of the structures from frozen slices and an extremely sensitive radioisotopic assay for the enzyme. About 20 cerebral regions were chosen for study because of their role in sensorimotor integration. Highest CAT activity was found in the basal ganglia, followed by the thalamus and the cerebral cortex. The cerebellum had the lowest level of CAT. Special detailed studies were made in the substantia nigra, nucleus ventralis lateralis of the thalamus, areas 4 and 6 of the cerebral cortex, the red nucleus in the mesencephalon and the deep cerebellar nuclei in order to define the intranuclear distribution of their cholinergic innervation.

Animals↗
PubMed1980

Effects of alpha-chloralose on the activity of the nigrostriatal dopaminergic system in the cat.

The effects of alpha-chloralose anaesthesia were studied in the cat on the release of 3H-dopamine (#H DA) from the caudate nucleus and the substantia nigra using the push-pull cannula method and continuous labelling of the structures with L-3,5-3H-tyrosine. Results were compared to those obtained under the same experimental conditions in both halothane-anaesthetized animals and 'encéphale isolé' preparations. The alpha-chloralose-anaesthetized preparation showed the lowest level of 3H-DA release, both from dopaminergic nerve terminals in the caudate nucleus and from dendrites of dopaminergic neurons in the substantia nigra. Furthermore, the time required to reach a steady-state release of 3H-DA was longer in alpha-chloralose-anaesthetized cats than in animals under halothane. This indicated that the activity of the dopaminergic neurons is depressed under alpha-chloralose anaesthesia. In the second part of the study, we measured the effects of unilateral somatic stimulation on the release of 3H-DA from the caudate nuclei and substantiae nigrae on both sides of the brain. The results show that under alpha-chloralose anaesthesia, the electric stimulation of the paw of the right forelimb does not significantly affect the release of 3H-DA from any of the above four structures. This contrasts with the changes of 3H-DA release seen in the same experimental conditions under halothane anaesthesia.

Animals↗
PubMed1980

Changes in dopamine release in caudate nuclei and substantia nigrae after electrical stimulation of the posterior interposate nucleus of cat cerebellum.

The effect of unilateral electrical stimulation of the posterior interposate nucleus of the cerebellum was examined on the activity of the nigro-striatal dopaminergic pathways on both sides of the brain in alpha-chloralose anaesthetized cats. Push-pull cannulae were inserted into both caudate nuclei and both substantia nigrae to measure the release of [3H]dopamine ( [3H]DA) which was continuously synthesized from L-[3,5-3H]tyrosine. The stimulation of the cerebellum induced long-lasting well-organized changes in [3H]DA release in the four structures: an increased release of the neurotransmitter in both the contralateral caudate nucleus and the ipsilateral substantia nigra and a reduction in the release of DA from the ipsilateral caudate nucleus and the contralateral substantia nigra. This finding supports the concept of a functional interaction between the cerebellum and the basal ganglia.

Animals↗
PubMedDate not supplied

Putative neurotransmitters in the red nucleus and their involvement in postlesion adaptive mechanisms.

A variety of putative neurotransmitters has been described in the red nucleus (RN). Measurement of neurotransmitter biochemical markers and study of their specific localizations using morphological techniques in lesion and deafferentation of the RN indicate the participation of glutamate (Glu) in corticorubral transmission and the presence of GABA in RN intrinsic neurones. The cerebellorubral projection may contain at least two populations of fibres, the one using acetylcholine and the other Glu as neurotransmitter. The presence of a serotoninergic input was also demonstrated. Selective deafferentations of the RN, particularly from its cerebellar input, result in biochemical and immunohistochemical responses indicative of increased corticorubral glutamatergic and local GABAergic transmission. These adaptive changes of neuronal transmission as well as the previously described sprouting of corticorubral nerve terminals may contribute to functional recovery after cerebellectomy in adult animals.

Animals↗