Caudal Neurons Research Articles

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.

Identification of neurotransmitters involved in responses of rat caudal medulla neurones to noxious and non-noxious facial stimuli and to stimulation of the periaqueductal gray (PAG)

Identification of neurotransmitters involved in responses of rat caudal medulla neurones to noxious and non-noxious facial stimuli and to stimulation of the periaqueductal gray (PAG)

Responses of caudate neurons to acoustic stimulation in cats

Responses of 141 neurons of the caudate nucleus to acoustic stimuli — tones (500 and 2000 Hz) and clicks of different frequency (0.2 and 0.8/sec) and intensity (75, 80, 95 dB) — were recorded extracellularly in chronic experiments on cats. The responses recorded showed great variability with respect to character (phasic, tonic), structure (one or two phases of excitation), latent periods (from 7.5 to 300.0 msec), and burst discharge frequency (from 90 to 800 spikes/sec). Analysis of averaged poststimulus histograms and graphs of the dynamics of the responses showed that responses of 74% of neurons were much better expressed if less frequent stimuli were used: The regularity of the responses and the number of spikes in each response increased. Responses of neurons also increased and acquired a more distinct temporal structure if the intensity of the clicks increased. The character of responses to clicks and tones differed qualitatively in 17% of neurons studied: Phasic excitation arose in response to clicks, tonic changes in spike activity to tones. The particular features of responses of caudate neurons to acoustic stimulation with different parameters are discussed.

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.

Raphe and periaqueductal gray induced suppression of non-nociceptive neuronal responses in the dorsal column nuclei and trigeminal sub-nucleus caudalis

Electrical stimulation of the feline periaqueductal gray matter and nucleus raphe magnus was found to inhibit the firing of trigeminal sub-nucleus caualis nocipeptive neurons, as has been previously reported. However, stimulation at these same sites using similar current intensities was also found to be equally effective in inhibiting the responses of non-nociceptive neurons in both nucleus caudalis and in the dorsal column nuclei.

Glycine enhancement of caudate neuronal activities: Relationship with the dopaminergic nigrostriatal pathway

Glycine microinjection into the substantia nigra zona compacta (SNC) in lightly anesthetized rats produced a marked and rapid decrease in spontaneous discharges of SNC neurons and a simultaneous enhancement of caudate nucleus (CN) activities. In animals pretreated with the dopamine receptor blocker, haloperidol, intranigral microinjection of glycine produced a dissociation of the nigral inhibition and caudate excitation. The SNC neurons were similarly suppresed with the CN neurons exhibited no discernible changes in firing frequency. A possible role was suggedted fro glycine as an inhibitory neurotransmitter acting on the cells of origin of the nigrostriatal pathway.

Development of spiny and aspiny neurons in the caudate nucleus of the dog during the first postnatal month.

The adult and developmental morphology of spiny and aspiny neurons in the dog caudate nucleus was examined using the Golgi-Kopsch technique. In the adult, three types each of spiny and aspiny neurons were identified based upon dendritic morphology and cell soma size. They corresponded in large part to those neurons described previously in the caudate nuclei of the rat, cat, and monkey. At birth, dendrites of spiny neurons possessed varicosities, filopodia, and thick proximal dendritic stumps--all characteristic of immaturity. Maturation of these processes involved the thinning of proximal dendrites, lengthening of dendritic shafts, and growth of dendritic spines. Although most of the dendritic maturation occurred during the first postnatal month, spine densities and dendritic lengths of spiny I neurons at 30 days were still less than those seen in the adult. Aspiny I neurons were also immature at birth but lacked the filopodia and thicker proximal dendrites that characterized immature spiny neurons. Aspiny dendritic development involved primarily the lengthening of dendritic processes; by 30 days the aspiny I neurons were indistinguishable from those seen in the adult. These results suggest that dendritic development of spiny I neurons may extend well past the end of the first postnatal month and that studies investigating functional development in the caudate nucleus should consider the relatively extended time period required for maturation of these primary synaptic sites.

Long-term decreases in spontaneous firing of caudate neurons induced by amphetamine in cats

Long-term decreases in spontaneous firing of caudate neurons induced by amphetamine in cats

The role of the basal ganglia in controlling a movement initiated by a visually presented cue

This study examines the effects on single neurons in caudate nucleus and globus pallidus of a visual stimulus, which is a cue to begin a tracking movement involving the forelimb on the side contralateral to the recording site. The experiments were designed to examine the relationship between activity of single neurons in these structures and movement initiation. Four monkeys were prepared for chronic recording of single neurons. The animals were trained to perform a tracking task that involved flexion and extension of the wrist at the onset of visual cue. The activities of a large proportion of neurons examined were correlated with the task, the proportion being greater in globus pallidus than in caudate nucleus. The majority of correlated neurons were activated after the onset of muscle activity and subsequent movement. It is thus unlikely that these cells were involved in movement initiation. However a role in movement execution is not excluded by the results. The fact that many cells were responsive only to certain specific conditions of the visual cue trial suggests an influence on these cells by highly processed visual information from other brain areas.

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.

Slow rhythmic activity of caudate neurons in the cat: Statistical analysis of caudate neuronal spike trains

Spike trains of caudate neurons initially having mean interspike intervals of less than 4 ms were analyzed with progressive administration of pentobarbital (5 to 20 mg/kg). Among the neurons investigated, 77% ( N = 79) showed evidence of a rhythmic basis of their activity in first-order interspike interval histograms and/or autocorrelation histograms in the course of becoming silent due to progressive administration of pentobarbital. Although the rhythmicies of given units varied depending on the level of anesthesia the most prominent cycle was almost always within the range of 200 to 320 ms; the majority were not discernable on visual inspection of the spike trains. Cortical stimuli reset the cycle. Cross-correlation histograms constructed from pairs of caudate neurons provided some evidence that their spontaneous firing was mutually inhibited. The possibility that the rhythmicities might arise from such mutual inhibition of spontaneously firing caudate neurons is discussed.

The spontaneous firing patterns of forebrain neurons. V. Time course of changes in caudate unit activity following dopamine-depleting lesions

The effects of unilateral medial forebrain bundle (‘MFB’) lesions on the spontaneous firing patterns of caudate neurons on both sides of the brain in cats were studied 3 days, 7 days and more than 2 weeks postlesion. Our results indicate that: (1) the spontaneous firing of neurons in the caudate nucleus ipsilateral to the lesion slows significantly by 3 days postlesion and returns to control values by 7 days postlesion, (2) the spontaneous activity of contralateral caudate neurons slows progressively with postlesion time and (3) these changes in neural activity are not correlated with changes in dopamine concentrations in the caudate nucleus.

Hypothalamic input to brain stem neurons responsive to oropharyngeal stimulation

The aim of this study was to determine if electrical stimulation of diencephalic sites previously implicated in feeding behavior and metabolic homeostasis could influence the unit activity of caudal brain stem neurons receiving oropharyngeal input. Electrical stimulation of the chorda tympani nerve (CT) was used to first identify brain stem units. A significant number of these CT-responsive neurons could also be driven by lateral hypothalamic area (LHA) stimulation. Medially placed diencephalic stimulating electrodes were not effective in altering unit activity of CT-responsive brain stem neurons. Tests of temporal summation showed that LHA conditioning pulses could significantly alter brain stem unit responses to CT test pulses at short interpulse intervals. These results demonstrate the presence of descending input from the LHA-medial forebrain bundle (MFB) to brain stem neurons possibly involved in oropharyngeal sensation and gustatory-evoked phenomena.

Interactions between p-tyramine, m-tyramine, or β-phenylethylamine and dopamine on single neurones in the cortex and caudate nucleus of the rat

p-Tyramine, applied to cortical and caudate neurones with weak iontophoretic currents (0-10 nA), did not usually cause any alteration of base-line firing rate. However, neuronal responses to dopamine (DA) during such weak applications of p-tyramine were greatly enhanced. Cortical neurone responses to noradrenaline (NA) were similarly potentiated, but both cortical and caudate neurone responses to alpha-aminobutyric acid were unaffected by p-tyramine. In addition, weak background applications of DA which did not affect cell firing rate were also without effect on the neuronal responses to the standard application of DA. The responses of cortical neurones to DA were also potentiated by m-tyramine and beta-phenylethylamine applied with weak cationic currents. The results may suggest that trace amines can enhance NA and DA transmission in the central nervous system.

Change in catecholamine-sensitive Na+,K+-ATPase activity in the rat striatum microsomes following electrolytic or 6-hydroxydopamine-induced lesions of dopaminergic neurons.

Ungerstedt (1) demonstrated that the degeneration of nigrostriatal dopamine (DA) system by microinjection of 6-hydroxydopamine (6-OHDA) produced a postsynaptic supersensitivity to inhibitory action of DA in the caudate neurons. Since then, there have been a number of reports concerned with the development of supersensitivity to DA in the caudate neurons following various procedures, e.g. surgical or chemical denervation of nigrostriatal DA neurons, sustained attenuation or blockade of dopaminergic transmission, etc. (2–6). DA stimulates the synthesis of cyclic AMP in the caudate nucleus (7) and, there is controversy about the role of adenylate cyclase in the development of supersensitivity (8–10).

Change in Catecholamine-Sensitive Na+,K+-ATPase Activity in the Rat Striatum Microsomes Following Elegtrolytic or 6-Hydroxydopamine-Induced Lesions of Dopaminergic Neurons

Ungerstedt (1) demonstrated that the degeneration of nigrostriatal dopamine (DA) system by microinjection of 6-hydroxydopamine (6-OHDA) produced a postsynaptic supersensitivity to inhibitory action of DA in the caudate neurons. Since then, there have been a number of reports concerned with the development of supersensitivity to DA in the caudate neurons following various procedures, e.g. surgical or chemical denervation of nigrostriatal DA neurons, sustained attenuation or blockade of dopaminergic transmission, etc. (2–6). DA stimulates the synthesis of cyclic AMP in the caudate nucleus (7) and, there is controversy about the role of adenylate cyclase in the development of supersensitivity (8–10).

Effects of iontophoretic 5-hydroxytryptamine on the unitary discharge frequency of caudate nucleus neurons in the rat.

Microiontophoretic application of 5-hydroxytryptamine (5-HT) on rat caudate nucleus neurons has both facilitatory and inhibitory effects on the discharge frequency of the neurons; in many cases 5-HT has a two-phase action. An analysis was made of the behaviour of facilitatory and inhibitory responses in time considering the mean firing rate variations during and after 5-HT iontophoretic release. The experimental results were statistically elaborated.

Responses of caudate neurons to clicks in chronic experiments on cats

Spontaneous and evoked unit activity in response to repeated application of clicks at a frequency of 0.3–2.0 Hz in the caudate nucleus was studied by an extracellular recording technique in chronic experiments on cats. Four types of spontaneous unit activity in the caudate nucleus were distinguished. Altogether 44% of neurons tested responded by changes in spontaneous activity to clicks. Five types of responses of caudate neurons to clicks were discovered: phasic excitation, phasic inhibition, tonic activation, tonic inhibition, and mixed tonic responses; the commonest type was tonic activation. During prolonged stimulation by clicks extinction of the phasic responses was not observed. Complete or partial extinction of tonic responses in the course of frequent repetition of stimulation was observed in 33% of responding neurons. The question of possible convergence of specific and nonspecific influences on caudate neurons is discussed.

Incorporation of intrastriatally injected [ 3H]fucose into electrophoretically separated synaptosomal glycoproteins. I. Turnover and molecular weight estimations

The radioactivity profiles of electrophoresed neostriatal P2 fraction glycoproteins were examined at a series of times (2.5, 3 and 4 h; 1, 5 and 10 days) following intracranial injections of [3H]fucose into the neostriatum. Ten major fucosylglycoprotein peaks were discerned in these profiles and certain aspects of their metabolism were characterized. The half-life of fucosylglycoproteins in the P2 fraction was estimated to be 9.7 days. The half-lives of the individual glycoprotein peaks ranged from 4.9 to 17.9 days. The apparent molecular weights of the glycoprotein peaks obtained by our procedures ranged from 32,000 to 180,000 daltons. One peak (peak VIII) incorporated radioactivity primarily at short intervals following the injection. The time course of [3H] fucose incorporation into this peak suggests involvement in the transport, activation and/or incorporation of fucose in brain. Since intracranial injections of [3H]fucose are incorporated into proteins in the cell body, synaptosomal fractions from caudate neurons alone are labeled by this technique. This may be useful in separating pre- and postsynaptic glycoprotein biochemistry. Finally, we tentatively propose that the glycoprotein peaks observed in neostriatum may be identical to previously isolated glycoproteins of known function or subcellular location.

Inhibitory effects of nucleus raphe magnus on neuronal responses in the spinal trigeminal nucleus to nociceptive compared with non-nociceptive inputs

The effect of stimulation in nucleus raphe magnus on neurones in the spinal trigeminal nucleus was studied in decerebrate cats. Short trains of raphe stimulation reduced or abolished the responses of neurones in nucleus oralis and nucleus caudalis to nociceptor stimulation (tooth pulp or cornea) but had a much weaker or insignificant effect on responses to non-noxious inputs (hair movement or low intensity stimulation of the infraorbital nerve). Maximum inhibition was seen 10--50 msec following the raphe stimulation and persisted up to 300 msec. The depression of neuronal responses was paralleled by an increase in the threshold of the jaw-opening reflex evoked by tooth pulp stimulation. The relation to stimulus-produced analgesia is discussed.