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  • Electrophysiology  (2)
  • 6-hydroxydopamine  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Muscarinic action of acetylcholine in the rat ventromedial thalamic nucleus (1984)
    Springer
    Experimental brain research 55 (1984), S. 553-561 
    Details
    ISSN: 1432-1106
    Keywords: Thalamus ; Electrophysiology ; Iontophoresis ; Acetylcholine ; Choline acetyltransferase ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Several lines of evidence suggest a role for ACh in the mediation of cerebello-thalamic transmission. The physiological, pharmacological and biochemical experiments described were designed to test this hypothesis for the rat cerebello-thalamic pathway. Unilateral electrolytic lesions of the superior cerebellar peduncle resulted in modest falls of CAT from both ventromedial thalamic nuclei (contralateral 35%, ipsilateral 15%). Iontophoretic application of ACh to relay cells evokes three types of response (i) excitation (ii) inhibition (iii) polyphasic combinations of (i) and (ii). The type of response evoked was directly related to the firing pattern of the cell. Thus, for example, excitatory responses were never recorded during high-frequency bursting but were easily evoked following a switch to tonic, single-spike activity. All responses to ACh and synaptic responses to cerebellar stimulation were sensitive to muscarinic but not to nicotinic cholinergic antagonists. The nicotinic antagonist mecamylamine was a potent blocker of excitant amino acid responses but had no effect on cerebellarevoked synaptic responses. Cholinergic and anticholinergic agents had a profound action on relay cell firing pattern. ACh promoted single-spike activity whereas atropine promoted high-frequency bursting. The actions of ACh are discussed with reference to recently discovered voltage-sensitive ionic conductances. Because of the modulatory action of ACh on relay cell firing pattern and excitability no firm conclusion can be reached concerning the hypothesis under test here. We tentatively suggest a dual role for ACh as both neurotransmitter and neuromodulator.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235286
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dysfunction of the midbrain angular complex can accentuate or attenuate circling behaviour in the rat (1985)
    Springer
    Experimental brain research 58 (1985), S. 45-55 
    Details
    ISSN: 1432-1106
    Keywords: Apomorphine ; Muscimol ; Electrolesion ; Circling ; Holeboard ; 6-hydroxydopamine ; γ-vinyl GABA ; Angular complex ; Stereotypy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of the midbrain angular complex (AC) in the execution of motor behaviours was investigated in the rat. In an automated holeboard apparatus bilateral AC electrolesions attenuated exploration and increased locomotor performance of drug-free rats on the first and second test occasions respectively; the latter result may signify a retarding of between-session habituation. Apomorphine also decreased locomotion and almost abolished head dipping and rearing in the holeboard; bilateral AC lesions reinstated locomotion to a normal level without modifying the other behavioural parameters. An electrolesion of one AC did not affect the animal's posture or spontaneous locomotion in the open field, but gave rise to pronounced ipsiversive circling when coupled with systemic administration of apomorphine. In unilaterally 6-hydroxydopamine (6-OHDA) treated rats subcutaneous injection of apomorphine evoked robust contraversive circling. A concomitant lesion of the ipsilateral AC introduced an additional ipsilateral bias to these animals' movements; contraversive circling was initially curtailed and posture reduced (or reversed), while stereotyped activities (particularly grooming) were suppressed. Contralateral orientation and circling were restored by subsequently lesioning the contralateral AC as well; bilateral AC lesions significantly potentiated circling to systemic apomorphine. Contralateral locomotor asymmetry was also produced by depositing apomorphine stereotaxically into the supersensitive caudate, or by microinjecting one substantia nigra zona reticulata with muscimol (in naive rats). Both rotational responses were facilitated by injury to the ipsilateral AC. The effects of electrocoagulating the AC were generally duplicated by discrete microinjection of muscimol or γ-vinyl GABA into this area, suggesting GABA-mediated synapses are normally operative in this part of the brain. These results do not support the claim that the AC is specifically engaged in mediating postural asymmetry in the unilaterally 6-OHDA denervated rat. Instead, we believe that impairment of neurotransmission through one AC imposes an independent and reciprocal tendency to move towards that side of the brain, as well as attenuating stereotypy and facilitating locomotion. The resultant behavioural response to systemic apomorphine shown by animals bearing these two types of lesion embodies these separate actions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238952
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for a GABAergic nigrothalamic pathway in the rat (1980)
    Springer
    Experimental brain research 40 (1980), S. 55-61 
    Details
    ISSN: 1432-1106
    Keywords: Substantia nigra ; Thalamus ; Inhibition ; GABA ; Electrophysiology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular recordings were made from neurones in the ventromedial and parafascicular nuclei of the rat thalamus, many of which had demonstrable capsular or caudate projections. These cells responded to electrical stimulation of the ipsilateral substantia nigra with a short latency (4 ms) inhibition presumed to be monosynaptic. This inhibitory response was often preceded by a brief period of increased excitability (latency ∼3 ms) attributed to activation of corticofugal collaterals. Longer latency, presumably oligosynaptic excitations (latency ∼8 ms) and inhibitions (∼18 ms) were also obtained, but were more commonly evoked in non-projection neurones. All units were inhibited by iontophoretically applied GABA, glycine or 5-HT. Short and long latency synaptic and GABA-induced inhibitions were selectively blocked by bicuculline. Strychnine only antagonised glycine, while 5-HT was not affected by either convulsant. Intranigral injection of muscimol greatly elevated the spontaneous discharge rate of thalamic neurones, particularly those with a striatal projection. These data are compatible with nigrothalamic neurones maintaining a tonically active, GABA-mediated inhibition of cells in the ventromedial and parafascicular nuclei of the thalamus. It is speculated that intranigral muscimol indirectly activates these thalamic cells and thereby initiates contraversive circling behaviour by suppressing this inhibitory system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236662
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    Paper (German National Licenses)
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