Cat Caudate Neurons Research Articles

Activity change of cat caudate neurons related to the learning of memory-guided saccade task

Activity change of cat caudate neurons related to the learning of memory-guided saccade task

2220 Activity change of cat caudate neurons related to the learning of memory-guided saccade task

2220 Activity change of cat caudate neurons related to the learning of memory-guided saccade task

1655 The activity of cat caudate neurons associated with memory-guided eye movement task

1655 The activity of cat caudate neurons associated with memory-guided eye movement task

Neurophysiological, pharmacological and morphological properties of human caudate neurons recorded in vitro

Tissue samples from the caudate nucleus were obtained from eight children (eight to 172 months of age) who underwent hemispherectomies for the relief of intractable seizures. Neurophysiological, pharmacological and morphological properties of caudate neurons were characterized by intracellular recordings in an in vitro slice preparation. These properties were compared with those of tissue obtained from animal studies. Electrophysiological properties of human caudate neurons that were similar to those of cat caudate and rat neostriatal cells included resting membrane potential, input resistance, action potential rise time, fall time, duration and action potential afterhyperpolarization amplitude, as well as the general characteristics of locally evoked synaptic responses. Properties that were different included action potential amplitudes and time-constants. Human caudate neurons also displayed responses similar to those of cat caudate or rat neostriatal cells to manipulation of excitatory amino acid receptor systems and to dopamine application. Kynurenic acid, a broad-spectrum excitatory amino acid receptor antagonist, decreased the amplitude of evoked synaptic responses, indicating that they were partially mediated by excitatory amino acids. In Mg 2+ free Ringer's solution, the amplitudes and durations of postsynaptic responses were increased and bursts of action potentials were induced. These effects were mediated by activation of N-methyl- d-aspartate receptors since they were blocked by 2-amino-5-phosphonovalerate, a specific N-methyl- d-aspartate-receptor antagonist. Iontophoretic application of N-methyl- d-aspartate also induced membrane oscillations and bursts in almost all caudate neurons. Dopamine decreased the amplitude of postsynaptic responses, an effect antagonized by domperidone, a selective D 2 dopamine receptor antagonist. Developmentally, the greatest change was an increase in action potential amplitude, although input resistance decreased and action potential afterhyperpolarization amplitude increased. Postsynaptic responses were similar across age. All but one of the caudate neurons identified by intracellular injection of biocytin or Lucifer Yellow were medium-sized spiny cells. These experiments show that human caudate neurons display a number of electrophysiological properties similar to rat neostriatal or cat caudate neurons recorded in brain slices. Furthermore, few electrophysiological parameters changed significantly over the age period examined suggesting that the human caudate at eight months displays many of the neuronal functions of the more mature caudate nucleus.

Neurophysiological maturation of cat substantia nigra neurons: Evidence from in vitro studies

The membrane properties and synaptic physiology of developing cat substantia nigra (SN) neurons were studied in in vitro slice preparations. Stable intracellular recordings were obtained from 46 neurons in 20 kittens ranging in age from fetal day (F) 51 to postnatal day (P) 120. Only two of these properties changed with development. The percentage of cells displaying inward rectification and the percentage of cells that generated low-threshold Ca++ spikes increased with age. Properties that did not change included resting membrane potentials, action potential amplitudes and durations, and input resistances. At all ages locally evoked synaptic responses consisted of sequences of excitatory postsynaptic potentials followed by inhibitory postsynaptic potentials. Most of the cells recorded had the electrophysiological properties which have been attributed to SN dopamine-containing neurons. To identify neurons morphologically, and verify the recording site, cells were filled with Lucifer yellow at the end of each experiment. Somatic shapes varied widely from oval to fusiform to triangular. Somatic diameters and dendritic length increased with development. Filopodial processes and growth cones were present up to the first postnatal month. Dye-coupling occurred only in the fetal group. These results indicate that cat SN neurons have many mature physiological properties during late fetal and early postnatal development. This contrasts with the significant maturation that occurs in cat caudate neurons during the same developmental period.

Neurophysiological maturation of cat caudate neurons: Evidence from in vitro studies

The membrane properties and synaptic physiology of developing cat caudate (Cd) nucleus neurons were studied in in vitro slice preparations. Recordings were obtained from 98 cells in kittens from fetal day (F) 56 to postnatal day (P) 90. With increasing age, the following maturational changes occurred; resting membrane potentials became more negative, action potential rise times decreased, action potential amplitudes increased, and action potential durations and input resistances decreased. The frequency of occurrence of afterhyperpolarizations and of anomalous rectification increased with age. The primary response to local extracellular stimulation was a depolarization usually accompanied by an action potential. Evoked hyperpolarizing responses were seen after P28 but only occurred if the membrane was depolarized by intracellular current injection. Cells identified by intracellular injection of Lucifer yellow were primarily medium-sized spiny neurons although it was not always possible to determine the cell type in slices from animals less than P5. Somatic diameter, dendritic length, and spine density increased with age. Dye-coupling occurred in slices less than P20. Its frequency decreased with age. These results show that Cd neurons undergo significant maturation during late prenatal and early postnatal periods. In contrast, substantia nigra neurons mature more rapidly and should be capable of influencing the less mature Cd neurons during development.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic NMDA exposure of developing cerebellar granule cells decreases their sensitivity to NMDA : M. Didier 1, F.A. Rassendren 2, J.M. Mienville 1, P. Soubrié 1, J. Bockaert 1 and J.P. Pin 3. 1SANOFI RECHERCHE ligne neuropsychiatrie, 2CNRS CRBM UPR41, INSERM U249, 3CCIPE Montpellier France

Responses evoked byl-cysteine-sulphinate (l-CSA) andl-aspartate (l-Asp) were recorded with intracellular electrodes from caudate neurons in halothane anesthetized cats.l-CSA andl-Asp were applied microiontophoretically to caudate cells and their effects on membrane and action potentials, as well as on cortically evoked synaptic potentials were evaluated.l-CSA andl-Asp induced depolarizations accompanied by regular firing resembling kainate (KA)- or quisqualate (QUIS)-induced excitation patterns (type 1) in 82% and 72% of the recorded neurons, respectively, and a mixed pattern consisting of aN-methyl-d-aspartate (NMDA)-like excitation (type 2) followed by a regular type 1 pattern in the remaining cells. In about a quarter of the cells the effects ofl-CSA andl-Asp, but not those of KA or QUIS, were partially antagonized by 2-amino-7-phosphonoheptanoate (AP-7), a specific NMDA receptor antagonist. Kynurenate, a broad spectrum excitatory amino acid antagonist, blocked responses elicited by eitherl-CSA or QUIS. The actions ofl-CSA andl-Asp on the firing pattern and membrane potential of cat caudate neurons in situ provide evidence in favor of their mixed agonist nature with respect to NMDA and non-NMDA excitatory amino acid receptors.

Differential effects of ( d)- and ( l)-homocysteic acid on the membrane potential of cat caudate neurons in situ

The enantiomers of homocysteic acid have been applied by microiontophoresis to neurons of the cat caudate nucleus in situ. The ( l)-enantiomer elicited a bursty firing pattern similar to the one caused by N-methyl- d-aspartate, but differing from the N-methyl- d-aspartate pattern inasmuch as ( l)-homo-cysteate induced depolarization shifts were shorter and had a smaller amplitude. ( l)-Homocysteate induced excitations could be strongly inhibited by the selective N-methyl- d-aspartate antagonist 2-amino-7-phosphonoheptanoic acid but they were less sensitive to this antagonist than N-methyl- d-aspartate itself. ( d)-Homocysteate elicited a more regular firing pattern similar to the one caused by non- N-methyl- d-aspartate excitatory amino acids such as quisqualate. These excitations were only rarely inhibited by 2-amino-7-phosphonoheptanoic acid. Our results suggest that ( l)-homocysteate, a transmitter candidate at central mammalian synapses, is a mixed excitatory amino acid agonist with a strong preference for N-methyl- d-aspartate receptors in the cat caudate nucleus, while ( d)-homocysteate has a predominant action at non- N-methyl- d-aspartate excitatory amino acid receptors.

Effects of l-cysteine-sulphinate and l-aspartate, mixed excitatory amino acid agonists, on the membrane potential of cat caudate neurons

Responses evoked by l-cysteine-sulphinate ( l-CSA) and l-aspartate ( l-Asp) were recorded with intracellular electrodes from caudate neurons in halothane anesthetized cats. l-CSA and l-Asp were applied microiontophoretically to caudate cells and their effects on membrane and action potentials, as well as on cortically evoked synaptic potentials were evaluated. l-CSA and l-Asp induced depolarizations accompanied by regular firing resembling kainate (KA)- or quisqualate (QUIS)-induced excitation patterns (type 1) in 82% and 72% of the recorded neurons, respectively, and a mixed pattern consisting of a N-methyl- d-aspartate (NMDA)-like excitation (type 2) followed by a regular type 1 pattern in the remaining cells. In about a quarter of the cells the effects of l-CSA and l-Asp, but not those of KA or QUIS, were partially antagonized by 2-amino-7-phosphonoheptanoate (AP-7), a specific NMDA receptor antagonist. Kynurenate, a broad spectrum excitatory amino acid antagonist, blocked responses elicited by either l-CSA or QUIS. The actions of l-CSA and l-Asp on the firing pattern and membrane potential of cat caudate neurons in situ provide evidence in favor of their mixed agonist nature with respect to NMDA and non-NMDA excitatory amino acid receptors.

In vitro release and electrophysiological effects in situ of homocysteic acid, an endogenous N-methyl-(D)-aspartic acid agonist, in the mammalian striatum

A potassium-induced, calcium-dependent release of endogenous homocysteic acid (HCA) from rat striatal slices was demonstrated. A precolumn derivatization high-performance liquid chromatography method was developed that allowed quantitative determination of sulfur-containing amino acids at the picomole level. Intracellular recordings from cat caudate neurons during simultaneous microiontophoretic application of drugs and electrical stimulation of the corticocaudate pathway showed that (L)-HCA evoked a depolarization pattern similar to that induced by N-methyl-(D)-aspartic acid (NMDA), and both these depolarizations could be selectively inhibited by a specific NMDA antagonist, (D)-2-amino-7-phosphonoheptanoic acid [(D)-AP-7]. A selective antagonism of (L)-HCA-induced depolarizations by (D)-AP-7 was confirmed in quantitative experiments with the frog hemisected spinal cord in vitro. Small quantities of iontophoretically applied (L)-HCA, but not of quisqualate, potentiated cortically evoked EPSPs in cat caudate neurons. These observations suggest that (L)-HCA might be a candidate as an NMDA-receptor-preferring endogenous transmitter in the caudate nucleus. One possible function for such transmitter systems could be the enhancement of EPSPs.

Baclofen attenuates hyperpolarizing not depolarizing responses of caudate neurons in cat

The effects of baclofen, a γ-aminobutyric acid (GABA) analogue, were studied on the intracellular responses of caudate neurons to cortical and thalamic stimulation. Systemic or intracaudate injections of baclofen did not reduce the initial excitatory postsynaptic potential (EPSP) to these stimuli; however, it did completely block evoked hyperpolarizations. These results suggest that the GABA-b receptor (one possible site of baclofen action) is not found on the corticostriate synaptic terminals. Furthermore, our results clearly indicate that evoked hyperpolarizations recorded in caudate neurons are not the result of cortical disfacilitation.

Evidence for GABA as the transmitter for early cortically evoked inhibition of cat caudate neurons.

Bicuculline methochloride derived from (+) bicuculline was applied by microiontophoresis to intracellularly recorded cat caudate neurons during stimulation of the cortico-caudate pathway. This resulted in a distinct increase of the duration and amplitude of the evoked excitatory postsynaptic potentials and an increase of the delay to the following hyperpolarizations. In most cases, however, a residual hyperpolarization remained even after prolonged applications of bicuculline methochloride. Iontophoretic application of GABA usually reduced the amplitude of the cortically evoked depolarizations. Very similar effects were seen if bicuculline methochloride was applied to dorsal hippocampal neurons while the fimbria/fornix was stimulated, an augmentation of the evoked depolarizations with a concomitant reduction of the following evoked inhibition. From these observations it was concluded that GABA is very probably the transmitter for the early part of cortically evoked hyperpolarizations in cat caudate neurons and that one of its functions is to regulate the strength of cortically evoked excitation.

Effects of amphetamine on intracellular responses of caudate neurons in the cat

The effects of acute administration of amphetamine on membrane potentials and evoked postsynaptic potentials of caudate neurons in cats were assessed using intracellular recording. High doses of amphetamine (0.5 mg/kg, i.v.) produced a reversible depolarization of the cell membrane in 78% of cells tested. Low doses (0.1 mg/kg) had no effect on the resting membrane potential. Long-lasting increases in amplitude of both excitatory and inhibitory components of evoked postsynaptic potential sequences were observed after both high and low doses of amphetamine. These changes were more evident to cortical than to substantia nigra or to intralaminar thalamic stimulation. These results were shown to be independent of the peripheral autonomic actions of amphetamine. These effects appear to be mediated by the ability of amphetamine to alter catecholaminergic mechanisms in the caudate nucleus and suggest that increased dopamine release may have a facilitatory effect on both excitatory and inhibitory synaptic transmission.

Interaction between influences of functionally different cortical areas on caudate neurons in cats

Unit activity in the caudate nucleus evoked by paired stimulation of the anterior sigmoid and middle suprasylvian gyri was studied in acute experiments on cats. Responses in most neurons to testing stimulation of the anterior sigmoid gyrus during the period of inhibition of spontaneous activity evoked by conditioning stimulation of the suprasylvian gyrus were preserved, but in isolated cases they were actually facilitated. Meanwhile conditioning stimulation of the anterior sigmoid gyrus in the period of inhibition depressed responses to testing stimulation of the suprasylvian gyrus. Similar results were obtained in experiments on animals with deep transcortical sections between the sensomotor and parietal regions, ruling out the possibility of interaction between the stimulated zones at the cortical level.

Intracellular analysis of synaptic potentials in rat neostriatum following stimulation of the cerebral cortex, thalamus, and substantia nigra

Intracellular recordings were obtained from neostriatal neurons of unparalyzed male hooded rats anesthetized with urethane. Electrical stimulation of the cerebral cortex (Cx), centromedian-parafascicular area of the thalamus (CMP), and the substantia nigra (SN) elicited monosynaptic excitatory postsynaptic potentials (EPSPs) in neostriatal neurons. Response latencies were, on the average, 3.7 msec, 3.3 msec, and 3.8 msec, for Cx, CMP and SN stimulation, respectively. Over 85% of recorded neurons showed convergence of inputs from all three stimulation sites. The SN induced EPSP sometimes had two components, with the second component beginning 10–15 msec after the first. EPSPs from all three stimulation sites were often followed by inhibitory postsynaptic potentials (IPSPs) lasting from 50–250 msec. Double shock experiments indicated that SN induced EPSPs could be reduced in amplitude by 20–80% when preceded by conditioning stimulation to Cx, CMP or SN. In contrast, the EPSP elicited by Cx stimulation were unaffected by conditioning stimulation. Some recorded neurons were morphologically identified by means of intracellular injection of horseradish peroxidase. All were “medium spiny” neurons. The results of the present study agree well with those of previous studies of cat caudate neurons, and extend them to rat neostriatal neurons.

Iontophoretically applied dopamine depolarizes and hyperpolarizes the membrane of cat caudate neurons

Dopamine (DA) was applied iontophoretically on intracellularly recorded cat caudate neurons. Ejected approximately 100 μm away from the cell soma, it caused slow depolarizations of the membrane while the ongoing firing rate was reduced. This last effect was not due to sodium inactivation. Cortically evoked EPSP-IPSP sequences were inhibited during the depolarizations. The latency of cortically evoked action potentials was consistently increased during DA-ejections. These effects were blocked by fluphenazine, a relatively selective blocker of the DA-sensitive adenylate cyclase. Nevertheless, there are serious doubts as to the specificity of these actions of DA as a number of other substances like naloxone, nicotine, acetylcholine or glutamate-diethylester occasionally had very similar effects on membrane potential, firing rate and cortically evoked EPSP-IPSP sequences. If DA was applied nearer to the soma, approximately 50 μm away, 70% of the recorded neurons continued to display the slow depolarizations above described, while 30% of the cells now reacted by a hyperpolarization accompanied also by a reduced firing rate. If DA was applied for prolonged periods on such cells, the initial hyperpolarization was followed by the slow depolarization. The observation that during the slow depolarization there is a decrease in firing rate and amplitude of the cortically evoked IPSP is explained by the assumption that the region of the axon hillock is hyperpolarized by DA, and that the slow depolarization is a phenomenon restricted to the distant recording site and possibly to the dendritic region. None of the 74 responsive neurons displayed an increased firing rate when DA was ejected either continously, i.e. for more than 5 sec, or in short pulses of 50–500 msec.