Spontaneous unit activity of the monkey caudate nucleus under chronic experimental conditions

Spontaneous unit activity and changes in its statistical parameters during electrical stimulation of the palms at 25 or 50/min were studied in four monkeys under chronic experimental conditions. Altogether 337 recordings of the activity of 64 neurons for durations of 2 and 3 min were studied. The mean firing rate was relatively low (5.7 spikes/sec). As a rule the unit activity remained stable for several tens of minutes. It could change spontaneously to new patterns and again remain stationary. These transitions took place during recording of spontaneous activity and also during stimulation of the animal, but they were independent of it. Interspike interval histograms were varied and most were polymodal. Their pattern changed with changes in the firing rate of the neurons. The position of the modes along the time axis and the type of distribution were the most conservative characteristics of the histograms. The probability of appearance of intervals was highest at 30, 60, 90, and 210–240 msec. The presence of stable intervals with increased probability of appearance may be the result of the existence of chains of neurons in the caudate nucleus with fixed temporal parameters.     

Dopamine receptors in canine caudate nucleus

Summary Physiological, pharmacological, histochemical and biochemical studies indicate that dopamine receptors are heterogenous in the, central nervous system with each individual functions. This review describes pharmacological and biochemical characteristics of dopamine receptors, particularly in canine caudate nucleus, which have been studied in our laboratory with a brief comparison to the current studies by other workers in similar research fields.Two distinct dopamine receptors have been characterized by means of [³H]dopamine binding to the synaptic membranes from canine caudate nucleus. One of the receptors with a Kd of about 3 M for dopamine may be associated with adenylate cyclase and referred to as D, receptor. The other receptor with a Kd of about 10 nM for dopamine is independent of adenylate cyclase and referred to as D₂. A photochemical irreversible association of [³H]dopamine with the membraneous receptors makes it possible to separate D₁ and D₂ receptors from one another by gel filtration on a Sephadex G-200 column after solubilization with Lubrol PX. On the basis of selective inhibition of [³H]dopamine binding to D₁ and D₂ receptors, dopamine antagonists can be classified into three classes: D₁-selective (YM-09151-2), D₂-selective (sulpiride) and nonselective (haloperidol, chlorpromazine). Effects of these typical antagonists on the metabolism of rat brain dopamine suggest that D₁ receptor is more closely associated with the neuroleptic-induced increase in dopamine turnover. Studies with 28 benzamide derivatives and some classical neuroleptics reveal that apomorphine-induced stereotypy displays a greater association with D₁ than with D₂ receptors.Dopamine-sensitive adenylate cyclase in canine caudate nucleus can be solubilized with Lubrol PX in a sensitive form to either dopamine, Gpp(NH)p or fluoride. Sephadex G-200 gel filtration separates adenylate cyclase from D₁ receptors with a concomitant loss of dopamine sensitivity. Addition of the D₁ receptor fraction to the adenylate cyclase restores the responsiveness to dopamine. The solubilized dopamine-unresponsive adenylate cyclase can be further separated into two distinct fractions by a batch-wise treatment with GTP-sepharose: a catalytic unit which does not respond to fluoride, and a guanine nucleotide regulatory protein. The regulatory protein confers distinct responsiveness to Gpp(NH)p and fluoride upon adenylate cyclase. These results indicate that dopamine-sensitive adenylate cyclase is composed of at least three distinct units; D₁ receptor, guanine nucleotide regulatory protein and adenylate cyclase.     

Neural responses during anticipation of a primary taste reward

The aim of this study was to determine the brain regions involved in anticipation of a primary taste reward and to compare these regions to those responding to the receipt of a taste reward. Using fMRI, we scanned human subjects who were presented with visual cues that signaled subsequent reinforcement with a pleasant sweet taste (1 M glucose), a moderately unpleasant salt taste (0.2 M saline), or a neutral taste. Expectation of a pleasant taste produced activation in dopaminergic midbrain, posterior dorsal amygdala, striatum, and orbitofrontal cortex (OFC). Apart from OFC, these regions were not activated by reward receipt. The findings indicate that when rewards are predictable, brain regions recruited during expectation are, in part, dissociable from areas responding to reward receipt.     

Primary cultures of human caudate nucleus

It is possible to grow functional primary dissociated cultures and explants from stereotactic biopsies of human parkinsonian caudate nuclei. Two major classes of cells were identified on morphological grounds. The culture cells appear to be stimulated by an unidentified soluble factor(s) obtained from human fetal neuronal cells in vitro. Culture of primary neuronal and glial cells from human adult cerebral nuclei seems to be a useful tool for several research purposes and in particular for studying both trophic factor action and target effects on afferent neurons for prospective human brain grafting.     

Spatial organization of the caudate nucleus in dogs

The dog caudate nucleus was studied by the Nissl, Kluver-Barrera, and Golgi methods in the usual planes of section. A complex spatial organization of the caudate nucleus was established. Radial bundles of fibers form fibrous layers through which run blood vessels and in which large neurons (long-axon reticular and large short-axon smooth-dendritic) and also two types of small cells are located. In the mesh of the fibrous layers barrel-shaped concentrations of small (17.5 µm, about 2–4%, small short-axon smooth-dendritic) and medium-sized (25 µm, about 96–98%, long-axon densely branching spinous) cells can be observed. These concentrations have the appearance of two or three layers of elongated "barrels," their axis perpendicular to the surface of the internal capsule. The stria periventricularis of the caudate nucleus and certain others of its regions are less differentiated.     

Efferent connections of the caudate nucleus in cats

Structural and ultrastructural changes in the frontal areas of the cortex and in the region of the globus pallidus were investigated after local and extensive destruction of the caudate nucleus. It was shown by the Fink-Heimer method that after local injury to the caudate nucleus by means of electrodes implanted 2–16 months before electrolytic destruction, only a few degenerating fibers of medium and thin caliber were present. Extensive destruction of the caudate nucleus (without preimplantation of electrodes) was followed by massive degeneration of fibers of different caliber in the frontal area of the cortex. After local injury to the caudate nucleus numerous thin degenerating axons 0.5–0.6 µ in diameter and degenerating terminals were found in the region of the globus pallidus. Degenerative changes in the axo-dendritic and axo-somatic terminals followed the "dark" type of course. It is concluded that no considerable direct projections of neurons of the caudate nucleus are present in the cortex. Degenerating fibers of average caliber in frontal areas of the cortex after destruction of the caudate nucleus are evidently axons of thalamic neurons and not from cells of the damaged nucleus.A. A. Bogomol'ets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 7, No. 2, pp. 165–171, March–April, 1975.     

Pharmacological modification of evoked caudate nucleus potentials

To stimulation of the Substantia nigra the nucleus caudatoputamen of the rat responds with the release of a short-latent sum action potential that may serve to characterize the interaction between the two nuclear areas. The partly conflicting results reported in the literature about drug effects on this potential prompted us to examine the effectiveness of dopaminergic and cholinergic substances or their antagonists following systematic administration. Chloropromazine increases the amplitude of the potential, while apomorphine has a distinct antagonistic effect. Interesting appear to be the analogical effects of Tricuran, arecoline and apomorphine, and the furtherance of the chloropromazine effect by arecoline.     

Electrophysiological investigation of effect of pulvinar stimulation of caudate nucleus neurons that react to visual stimulation

Responses of caudate neurons to electrical stimulation of the afferent input from thepulvinar thalamic nucleus and to visual stimuli of various orientations were studied extracellularly in awake chronic cats. Activation responses dominated among reactions of these neurons. The response latencies have ranged from 4 to 85 msec for units with primary activation and from 20 to 150 msec for inhibited ones. The values are indicative of both rapidly and slowly conducting afferent pathways. A possibility of monosynaptic transmission in thepulvinarcaudate projections is also revealed.Pulvinar stimulation is found to be efficient for a significant (more than 50 percent) number of caudate neurons responding to visual stimuli, including orientation-selective cells. The mode of influences from other structures of the visual system (optic tract, area 17, the Clare-Bishop area) on caudate neurons responding topulvinar stimulation is described. The data are discussed with respect to the possible role of cortical and subcortical projections of the visual system in the creation of sensory specific responses of the caudate nucleus.A. A. Bogomolets Physiology Institute, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 520–529, September–October, 1991.     

Phenylalanine in the caudate nucleus of dopamine depleted rats

Dopamine depleting lesions of the substantia nigra result in a reduction of the striatal accumulation of 2-phenylethylamine following monoamine oxidase inhibition. It is established that this effect may not be due to a change in availability of aromaticL-amino acid decarboxylase in striatum. Nevertheless, the possibility remains that striatal concentrations of phenylalanine (the precursor of 2-phenylethylamine) may be altered by dopamine-depleting lesions. The present experiments assessed the effects of dopamine depletion induced by 6-OHDA (7 days following 8 g/4 l unilateral substantia nigra injection) on striatal concentrations of phenylalanine, dopamine, 5-hydroxytryptamine and their metabolites. In addition, the effects of reserpine-induced (10 mg kg^–1, 2h, sc) amine depletion on these striatal levels were also assessed. Under equivalent conditions reserpine is reported to increase striatal accumulationof 2-phenylethylamine. 6-OHDA induced a significant unilateral depletion of dopamine, DOPAC and HVA and increased 5-HIAA but had no significant effect on phenylalanine levels. Reserpine decreased dopamine and 5-hydroxytryptamine and increased DOPAC, HVA and 5-HIAA levels, no changes in phenylalanine were observed. This pattern of results was also observed when lesioned animals or reserpine-treated animals were pretreated with (-)-deprenyl (2 mg kg^–1, 2 hr, sc), the treatment previously used to induce accumulation of 2-phenylethylamine. These data indicate that changes in 2-phenylethylamine previously observed under these conditions may not simply be secondary to a change in striatal phenylalanine concentrations.     

The subcellular fractionation of the bovine caudate nucleus

Two synaptosomal fractions could be obtained from bovine caudate nucleus on sucrose density gradients one of which had a much greater capacity for high affinity choline uptake than the other but comparable amounts of CAT and choline kinase activity. Specific binding of QNB was widely distributed among all the subcellular fractions except the mitochondrial fraction and in quantitative terms by far the greatest amount was in the microsomal fraction. Only the microsomal fraction contained measurable amounts of glycerophosphocholine phosphodiesterase.This paper is dedicated to Dr. Derek Richter on his seventy-fifth birthday.     

Oxytocin in the rat caudate nucleus influences pain modulation

Our previous studies have demonstrated that oxytocin (OXT) in the central nervous system plays a role in pain modulation. Many studies have found that caudate nucleus (CdN) enriches OXT and OXT receptors by the methods of historadioautograph and gene expression. The communication was designed to investigate OXT effect in the rat CdN on pain modulation. The results showed that (1) intra-CdN microinjection of OXT receptor antagonist, desGly-NH₂, d(CH₂)₅[d-Tyr₂, Thr-sup-4]OVT decreased the pain threshold, whereas the local administration of OXT increased the pain threshold in a dose-dependent manner; (2) OXT receptor antagonist can attenuate the analgesic role induced intra-CdN administration of OXT; and (3) pain stimulation could increase OXT concentration in the CdN perfusion liquid. The data suggested that OXT in the CdN was involved in this pain process via OXT receptors.