Synaptic responses of propriospinal neurons to stimulation of the stepping strip of the dorsolateral funiculus in cats

1985 ◽  
Vol 17 (2) ◽  
pp. 195-202 ◽  
Author(s):  
O. V. Kazennikov ◽  
M. L. Shik ◽  
G. V. Yakovleva
Keyword(s):  
Dorsolateral Funiculus ◽  
Propriospinal Neurons ◽  
Stimulation Of ◽  
Synaptic Responses

Increase in extracellular dopamine levels during clozapine-induced potentiation in the hippocampal dentate gyrus of chronically prepared rabbits

2008 ◽  
Vol 86 (5) ◽  
pp. 249-256 ◽  
Author(s):  
Takashi Kubota ◽  
Itsuki Jibiki ◽  
Akira Ishikawa ◽  
Tomomi Kawamura ◽  
Sonoko Kurokawa ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
Nmda Receptor ◽  
Dentate Gyrus ◽  
Negative Symptoms ◽  
Clinical Effect ◽  
Perforant Path ◽  
Hippocampal Dentate Gyrus ◽  
Extracellular Dopamine ◽  
Stimulation Of ◽  
Synaptic Responses

We previously found that 20 mg/kg clozapine i.p. potentiated the excitatory synaptic responses elicited in the dentate gyrus by single electrical stimulation of the perforant path in chronically prepared rabbits. We called this phenomenon clozapine-induced potentiation and proved that it was an NMDA receptor-mediated event. This potentiation is presumably related to clozapine’s clinical effect on negative symptoms and cognitive dysfunctions in schizophrenia. In the present study, to investigate the mechanisms underlying clozapine-induced potentiation, we examined whether extracellular dopamine and 5-HT levels changed during the potentiation by using a microdialysis technique in the dentate gyrus. The extracellular concentrations of dopamine and 5-HT levels were measured every 5 min during all experiments. Extracellular 5-HT levels did not change, but dopamine levels eventually increased significantly during clozapine-induced potentiation. The increase in the dopamine levels occurred almost simultaneously with the induction of clozapine-induced potentiation. These results suggest that clozapine-induced potentiation is at least partly attributable to a dopamine-mediated potentiation of excitatory synaptic transmission. The present study implies that such phenomena occur also in the perforant path–dentate gyrus pathway.

Dynamics of Excitatory Transmitter Release: Analysis of Synaptic Responses in CA3 Hippocampal Neurons After Repetitive Stimulation of Afferent Fibers

1998 ◽  
Vol 79 (4) ◽  
pp. 1977-1988 ◽  
Author(s):  
Marco Canepari ◽  
Enrico Cherubini
Keyword(s):  
Transmitter Release ◽  
Hippocampal Neurons ◽  
Repetitive Stimulation ◽  
Patch Clamp Technique ◽  
Afferent Fibers ◽  
Presynaptic Mechanisms ◽  
Release Analysis ◽  
Excitatory Transmitter ◽  
Stimulation Of ◽  
Synaptic Responses

Canepari, Marco and Enrico Cherubini. Dynamics of excitatory transmitter release: analysis of synaptic responses in CA3 hippocampal neurons after repetitive stimulation of afferent fibers. J. Neurophysiol. 79: 1977–1988, 1998. The patch-clamp technique (whole cell configuration) was used to record excitatory postsynaptic currents (EPSCs) evoked by repetitive stimulation (4 pulses at 50-ms intervals) of afferent fibers in the stratum lucidum-radiatum. Different synaptic behaviors (EPSC patterns) were classified in terms of facilitation or depression of the mean amplitude of the second, third, and fourth EPSC with respect to the previous one. A large variety of EPSC patterns was observed by stimulating different afferent fibers. Experiments with the mGluR2/mGluR3 agonist 2-(2,3-dicarboxycyclopropyl)glycine (DCG-IV) (1 μM), a compound that reduces release at mossy but not at associative commissural fibers and therefore allows to identify the origin of synaptic responses, showed that particular EPSC patterns could not be associated to the activation of a specific type of synaptic input. To investigate the role of the probability of release in the dynamics of synaptic activity, the extracellular calcium concentration was varied from 0.8 to 4 mM in several experiments. EPSC patterns dominated by depression, characteristics of high release probability conditions, could be observed in the majority of the cases in the presence of higher calcium concentrations. A quantitative model for dynamics of transmitter release has been developed. Experimental results were compared with data computed with the model taking into account the probability of release and the time course of reavailability. This work indicates that short-term changes of presynaptic conditions occurring during a train of action potentials can account for the high variability of EPSC responses. The model that is proposed also suggests a general method of experimental data analysis to investigate the possible presynaptic mechanisms underlying long-lasting changes in synaptic efficacy.

Red Nucleus Stimulation Inhibits Within the Inferior Olive

1998 ◽  
Vol 80 (6) ◽  
pp. 3127-3136 ◽  
Author(s):  
K. M. Horn ◽  
T. M. Hamm ◽  
A. R. Gibson
Keyword(s):  
Inferior Olive ◽  
Red Nucleus ◽  
Salient Feature ◽  
Cutaneous Stimulation ◽  
Motor Pathways ◽  
Peripheral Stimulation ◽  
Dorsal Columns ◽  
Dorsolateral Funiculus ◽  
Somatosensory Responses ◽  
Stimulation Of

Horn, K. M., T. M. Hamm, and A. R. Gibson. Red nucleus stimulation inhibits within the inferior olive. J. Neurophysiol. 80: 3127–3136, 1998. In the anesthetized cat, electrical stimulation of the magnocellular red nucleus (RNm) inhibits responses of rostral dorsal accessory olive (rDAO) neurons to cutaneous stimulation. We tested the hypothesis that RNm-mediated inhibition occurs within the inferior olive by using stimulation of the ventral funiculus (VF) of the spinal cord in place of cutaneous stimulation of the hindlimb. Fibers in the VF terminate on hindlimb rDAO neurons, so inhibition of this input would have to occur within the olive. rDAO responses elicited by VF stimulation were inhibited by prior stimulation of the RNm, indicating that inhibition occurs within the olive. In contrast, evoked potentials recorded from the VF or dorsal columns following hindlimb stimulation were not affected by prior stimulation of RNm, indicating that stimulation of the RNm does not inhibit olivary afferents at spinal levels. RNm stimulation that inhibited rDAO responses had little effect on evoked somatosensory responses in thalamus, indicating that inhibition generated by activity in RNm may be specific to rDAO. To test limb specificity of RNm-mediated inhibition, conditioning stimulation was applied to the dorsolateral funiculus at thoracic levels, which selectively activates RNm neurons projecting to the lumbar cord. Stimulation at thoracic levels inhibited evoked responses from hindlimb but not forelimb regions of rDAO, suggesting that inhibitory effects of RNm activity are limb specific. Several studies have reported that olivary neurons have reduced sensitivity to peripheral stimulation during movement; it is likely that RNm-mediated inhibition occurring within the olive contributes to this reduction of sensitivity. Inhibition of rDAO responses by descending motor pathways appears to be a salient feature of olivary function.

Interaction of descending spinal sympathetic pathways and afferent nerves

1978 ◽  
Vol 234 (3) ◽  
pp. H223-H229
Author(s):  
S. M. Barman ◽  
R. D. Wurster
Keyword(s):  
Nerve Fibers ◽  
Nerve Activity ◽  
Afferent Nerves ◽  
Afferent Nerve Fibers ◽  
Somatosympathetic Reflex ◽  
Reflex Activation ◽  
Dorsolateral Funiculus ◽  
Ventrolateral Funiculus ◽  
Stimulation Of ◽  
Excitatory Pathway

With the use of computer-aided techniques, the interaction of descending spinal sympathetic pathways and afferent nerve fibers (cervical dorsal roots and tibial nerve) in regulation of thoracic (T2) preganglionic nerve activity was investigated in anesthetized, vagotomized, and paralyzed cats. High-frequency activation of a sympathoinhibitory pathway (ventrolateral funiculus) depressed the evoked discharges in the T2 preganglionic nerve elicited by stimulation of a sympathoexcitatory pathway (dorsolateral funiculus) and the spinal component of the somatosympathetic reflex. Submaximal evoked responses were also inhibited through baroreceptor reflex activation (blood pressure elevations up to 225 mmHg). Facilitation of the spinal component of the somatosympathetic reflex occurred during stimulation of the excitatory pathway. Carotid occlusion (baroreceptor inactivation) facilitated the submaximal evoked discharges from stimulation of the descending excitatory pathway. These data support the contention that sympathetic nerve activity can be modified by the integration of excitatory and inhibitory impulses at the spinal level.

Spinally mediated inhibition of abdominal and lumbar sympathetic activities

1988 ◽  
Vol 254 (4) ◽  
pp. R655-R658 ◽  
Author(s):  
R. F. Taylor ◽  
L. P. Schramm
Keyword(s):  
Sympathetic Nerve ◽  
Sympathetic Activity ◽  
Sympathetic Nerve Activity ◽  
Sympathetic Nerves ◽  
Grouped Data ◽  
Response Curves ◽  
Spinal Transection ◽  
Stimulus Response ◽  
Dorsolateral Funiculus ◽  
Stimulation Of

Renal, splenic, and lumbar sympathetic nerve activities were recorded in the paralyzed, anesthetized, artificially ventilated, and spinally transected rat. Electrical stimulation of the dorsolateral funiculus caudal to the spinal transection was used to generate stimulus-response curves for changes in sympathetic activity in each of the three sympathetic nerves using five stimulus frequencies. In all rats, spinal stimulation inhibited sympathetic activity in renal and splenogastric nerves by approximately 50%. In grouped data, threshold frequency for inhibition of renal and splenogastric sympathetic nerve activity was 5 Hz, and inhibitions were maximal (50-60%) at 10 Hz. In contrast, activity in the lumbar sympathetic chain was inhibited in only two of five rats, and grouped data did not exhibit any statistically significant inhibitions. We conclude that lumbar sympathetic activity which remains after spinal transection can be inhibited only marginally by spinal stimulation, which substantially reduces renal and splenogastric sympathetic activity.

Behavior of upper cervical inspiratory propriospinal neurons during fictive vomiting

1991 ◽  
Vol 65 (6) ◽  
pp. 1492-1500 ◽  
Author(s):  
S. Nonaka ◽  
A. D. Miller
Keyword(s):  
Firing Pattern ◽  
Impulse Activity ◽  
Abdominal Muscle ◽  
Lateral Funiculus ◽  
Upper Cervical ◽  
Spinal Segments ◽  
Propriospinal Neurons ◽  
Lumbar Cord ◽  
Stimulation Of

1. The role of upper cervical inspiratory (UCI)-modulated neurons in respiratory muscle control during vomiting was examined by recording the impulse activity of these neurons during fictive vomiting in decerebrate, paralyzed cats. Fictive vomiting was identified by a characteristic series of bursts of coactivation of phrenic and abdominal muscle nerves, elicited either by electrical stimulation of supradiaphragmatic vagal nerve afferents or by emetic drugs, which would be expected to produce expulsion of gastric contents in nonparalyzed animals. 2. Data were recorded from 43 propriospinal UCI neurons, located in the C1-C3 spinal segments near the border of the intermediate gray matter and lateral funiculus, which were antidromically activated with floating pin electrodes placed in the ipsilateral lateral funiculus, usually at T1-T3. Some cells (9/21 tested) were also activated from the upper lumbar cord (L1). During respiration, most neurons (n = 40) had an augmenting discharge pattern during inspiration. In addition, more than one-half (55%) fired tonically during the remainder of the respiratory cycle. About 40% of UCI neurons showed variations in their firing pattern during the noninspiratory portion of respiration. These latter two properties of UCI neurons were not observed in dorsal and ventral respiratory group (DRG and VRG-, respectively) bulbospinal inspiratory (I) neurons previously recorded under similar conditions. 3. During fictive vomiting, the firing pattern of most UCI neurons fell into one of three main categories. More than one-half (53%) were active in phase with bursts of phrenic discharge and were thus classified as Active-type cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Subthalamic Stimulation-Induced Synaptic Responses in Substantia Nigra Pars Compacta Dopaminergic Neurons In Vitro

1999 ◽  
Vol 82 (2) ◽  
pp. 925-933 ◽  
Author(s):  
Yuji Iribe ◽  
Kevin Moore ◽  
Kevin C. H. Pang ◽  
James M. Tepper
Keyword(s):  
Substantia Nigra ◽  
Glutamate Receptor ◽  
Dopaminergic Neurons ◽  
Reversal Potential ◽  
Substantia Nigra Pars Compacta ◽  
Inhibitory Effects ◽  
Synaptic Potentials ◽  
Stimulation Of ◽  
Synaptic Responses

The subthalamic nucleus (STN) is one of the principal sources of excitatory glutamatergic input to dopaminergic neurons of the substantia nigra, yet stimulation of the STN produces both excitatory and inhibitory effects on nigral dopaminergic neurons recorded extracellularly in vivo. The present experiments were designed to determine the sources of the excitatory and inhibitory effects. Synaptic potentials were recorded intracellularly from substantia nigra pars compacta dopaminergic neurons in parasagittal slices in response to stimulation of the STN. Synaptic potentials were analyzed for onset latency, amplitude, duration, and reversal potential in the presence and absence of GABA and glutamate receptor antagonists. STN-evoked depolarizing synaptic responses in dopaminergic neurons reversed at approximately −31 mV, intermediate between the expected reversal potential for an excitatory and an inhibitory postsynaptic potential (EPSP and IPSP). Blockade of GABAA receptors with bicuculline caused a positive shift in the reversal potential to near 0 mV, suggesting that STN stimulation evoked a near simultaneous EPSP and IPSP. Both synaptic responses were blocked by application of the glutamate receptor antagonist, 6-cyano-7-nitroquinoxalene-2,3-dione. The confounding influence of inhibitory fibers of passage from globus pallidus and/or striatum by STN stimulation was eliminated by unilaterally transecting striatonigral and pallidonigral fibers 3 days before recording. The reversal potential of STN-evoked synaptic responses in dopaminergic neurons in slices from transected animals was approximately −30 mV. Bath application of bicuculline shifted the reversal potential to ∼5 mV as it did in intact animals, suggesting that the source of the IPSP was within substantia nigra. These data indicate that electrical stimulation of the STN elicits a mixed EPSP-IPSP in nigral dopaminergic neurons due to the coactivation of an excitatory monosynaptic and an inhibitory polysynaptic connection between the STN and the dopaminergic neurons of substantia nigra pars compacta. The EPSP arises from a direct monosynaptic excitatory glutamatergic input from the STN. The IPSP arises polysynaptically, most likely through STN-evoked excitation of GABAergic neurons in substantia nigra pars reticulata, which produces feed-forward GABAA-mediated inhibition of dopaminergic neurons through inhibitory intranigral axon collaterals.

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