Intense inhibitory avoidance training increases nuclear-phosphorylated glucocorticoid receptors in neurons of CA1 of hippocampus and ventral caudate putamen

Corticosterone (CORT), the principal glucocorticoid in rodents, is released after stressful experiences such as training with high foot-shock intensities in the inhibitory avoidance task (IA). CORT reaches the glucocorticoid receptor (GR) located in almost all brain cells; the GR is subsequently phosphorylated at serine 232 (pGRser232). This has been reported as an indicator of ligand-dependent activation of the GR, as well as a requirement for its translocation into the nucleus for its transcription factor activity. The GR is present in the hippocampus with a high concentration in CA1 and dentate gyrus (DG), and a smaller proportion in CA3, and sparsely present in the caudate putamen (CPu); both structures are involved in memory consolidation of IA. To study the participation of CORT in IA, we quantified the ratio of pGR-positive neurons in both dorsal hippocampus (CA1, CA3 and DG) and dorsal and ventral regions of CPu of rats trained in IA, using different foot-shock intensities. Brains were dissected 60 min after training for immunodetection of pGRser232 positive cells. The results show that the groups trained with 1.0 and 2.0 mA had higher retention latencies than the 0.0 mA or 0.5 mA groups. An increase in the ratio of pGR-positive neurons was found in CA1 and ventral region of CPu only for the 2.0 mA trained group. These findings suggest that activation of GRs in CA1 and ventral CPu is involved in the consolidation of a stronger memory of IA, possibly through the modulation of gene expression.

GABAB receptor signaling in the caudate putamen is involved in binge-like consumption during a high fat diet in mice

Previous studies suggest that signaling by the gamma-aminobutyric acid (GABA) type B receptor (GABABR) is involved in the regulation of binge eating, a disorder which might contribute to the development of obesity. Here, we show that intermittent access to a high fat diet (HFD) induced binge-like eating behavior with activation of dopamine receptor d1 (drd1)-expressing neurons in the caudate putamen (CPu) and nucleus accumbens (NAc) in wild-type (WT) mice. The activation of drd1-expressing neurons during binge-like eating was substantially increased in the CPu, but not in the NAc, in corticostriatal neuron-specific GABABR-deficient knockout (KO) mice compared to WT mice. Treatment with the GABABR agonist, baclofen, suppressed binge-like eating behavior in WT mice, but not in KO mice, as reported previously. Baclofen also suppressed the activation of drd1-expressing neurons in the CPu, but not in the NAc, during binge-like eating in WT mice. Thus, our data suggest that GABABR signaling in CPu neurons expressing drd1 suppresses binge-like consumption during a HFD in mice.

GABAergic inputs from direct and indirect striatal projection neurons onto cholinergic interneurons in the primate putamen

Striatal cholinergic interneurons (ChIs) are involved in reward-dependent learning and the regulation of attention. The activity of these neurons is modulated by intrinsic and extrinsic γ-aminobutyric acid (GABA)ergic and glutamatergic afferents, but the source and relative prevalence of these diverse regulatory inputs remain to be characterized. To address this issue, we performed a quantitative ultrastructural analysis of the GABAergic and glutamatergic innervation of ChIs in the postcommissural putamen of rhesus monkeys. Postembedding immunogold localization of GABA combined with peroxidase immunostaining for choline acetyltransferase showed that 60% of all synaptic inputs to ChIs originate from GABAergic terminals, whereas 21% are from putatively glutamatergic terminals that establish asymmetric synapses, and 19% from other (non-GABAergic) sources of symmetric synapses. Double pre-embedding immunoelectron microscopy using substance P and Met-/Leu-enkephalin antibodies to label GABAergic terminals from collaterals of "direct" and "indirect" striatal projection neurons, respectively, revealed that 47% of the indirect pathway terminals and 36% of the direct pathway terminals target ChIs. Together, substance P- and enkephalin-positive terminals represent 24% of all synapses onto ChIs in the monkey putamen. These findings show that ChIs receive prominent GABAergic inputs from multiple origins, including a significant contingent from axon collaterals of direct and indirect pathway projection neurons.

Comparison of fMRI BOLD response patterns by electrical stimulation of the ventroposterior complex and medial thalamus of the rat

The objective of this study was to compare the functional connectivity of the lateral and medial thalamocortical pain pathways by investigating the blood oxygen level-dependent (BOLD) activation patterns in the forebrain elicited by direct electrical stimulation of the ventroposterior (VP) and medial (MT) thalamus. An MRI-compatible stimulation electrode was implanted in the VP or MT of α-chloralose-anesthetized rats. Electrical stimulation was applied to the VP or MT at various intensities (50 µA to 300 µA) and frequencies (1 Hz to 12 Hz). BOLD responses were analyzed in the ipsilateral forelimb region of the primary somatosensory cortex (iS1FL) after VP stimulation and in the ipsilateral cingulate cortex (iCC) after MT stimulation. When stimulating the VP, the strongest activation occurred at 3 Hz. The stimulation intensity threshold was 50 µA and the response rapidly peaked at 100 µA. When stimulating the MT, The optimal frequency for stimulation was 9 Hz or 12 Hz, the stimulation intensity threshold was 100 µA and we observed a graded increase in the BOLD response following the application of higher intensity stimuli. We also evaluated c-Fos expression following the application of a 200-µA stimulus. Ventroposterior thalamic stimulation elicited c-Fos-positivity in few cells in the iS1FL and caudate putamen (iCPu). Medial thalamic stimulation, however, produced numerous c-Fos-positive cells in the iCC and iCPu. The differential BOLD responses and c-Fos expressions elicited by VP and MT stimulation indicate differences in stimulus-response properties of the medial and lateral thalamic pain pathways.

Distribution of GABAergic interneurons and dopaminergic cells in the functional territories of the human striatum

Background

The afferent projections of the striatum (caudate nucleus and putamen) are segregated in three territories: associative, sensorimotor and limbic. Striatal interneurons are in part responsible for the integration of these different types of information. Among them, GABAergic interneurons are the most abundant, and can be sorted in three populations according to their content in the calcium binding proteins calretinin (CR), parvalbumin (PV) and calbindin (CB). Conversely, striatal dopaminergic cells (whose role as interneurons is still unclear) are scarce. This study aims to analyze the interneuron distribution in the striatal functional territories, as well as their organization regarding to the striosomal compartment.

Methodology/Principal Findings

We used immunohistochemical methods to visualize CR, PV, CB and tyrosine hydroxylase (TH) positive striatal neurons. The interneuronal distribution was assessed by stereological methods applied to every striatal functional territory. Considering the four cell groups altogether, their density was higher in the associative (2120±91 cells/mm³) than in the sensorimotor (959±47 cells/mm³) or limbic (633±119 cells/mm³) territories. CB- and TH-immunoreactive(-ir) cells were distributed rather homogeneously in the three striatal territories. However, the density of CR and PV interneurons were more abundant in the associative and sensorimotor striatum, respectively. Regarding to their compartmental organization, CR-ir interneurons were frequently found in the border between compartments in the associative and sensorimotor territories, and CB-ir interneurons abounded at the striosome/matrix border in the sensorimotor domain.

Conclusions/Significance

The present study demonstrates that the architecture of the human striatum in terms of its interneuron composition varies in its three functional territories. Furthermore, our data highlight the importance of CR-ir striatal interneurons in the integration of associative information, and the selective role of PV-ir interneurons in the motor territory. On the other hand, the low density of dopaminergic cells casts doubts about their role in the normal human striatum.

Refractive index measurement of acute rat brain tissue slices using optical coherence tomography

An optical coherence tomography (OCT) system employing a microelectromechanical system (MEMS) mirror was used to measure the refractive index (RI) of anatomically different regions in acute brain tissue slices, in which viability was maintained. RI was measured in white-matter and grey-matter regions, including the cerebral cortex, putamen, hippocampus, thalamus and corpus callosum. The RI in the corpus callosum was found to be ~4% higher than the RIs in other regions. Changes in RI with tissue deformation were also measured in the cerebral cortex and corpus callosum under uniform compression (20-80% strain). For 80% strain, measured RIs increased nonlinearly by up to 70% and 90% in the cerebral cortex and corpus callosum respectively. Knowledge of RI in heterogeneous tissues can be used to correct distorted optical images caused by RI variations between different regions. Also deformation-dependent changes in RI can be applied to OCT elastography or to mechanical tests based on optical imaging such as indentation tests.

Analysis of the effects of cannabinoids on identified synaptic connections in the caudate-putamen by paired recordings in transgenic mice

CB(1) cannabinoid receptors are expressed in many neurons in the caudate-putamen. However, it is not known how the activation of these receptors influences synaptic transmission between different neuron classes. The aim was to establish a method for studying identified synaptic connections in the caudate-putamen, and to determine the effects of cannabinoids on these connections. Brain slices were prepared from transgenic mice expressing enhanced green fluorescent protein (EGFP) in parvalbumin-positive fast spiking interneurons (PV-FSNs). PV-FSNs were identified based on their fluorescence. Non-fluorescent medium-sized neurons were considered to be medium spiny neurons (MSNs). Synaptic transmission was studied by simultaneous patch-clamp recording from identified neuron pairs. In the case of PV-FSN --> MSN neurotransmission, the synthetic cannabinoid receptor agonist WIN55212-2 lowered the success rate of transmission and the amplitude of successful postsynaptic events. Analysis of miniature inhibitory postsynaptic currents indicated that WIN55212-2 inhibited synaptic transmission presynaptically. WIN55212-2 did not elicit somatodendritic effects in PV-FSNs: membrane potential, membrane current and evoked firing were not changed. WIN55212-2 also depressed the MSN --> MSN neurotransmission. The inhibitory synaptic input to MSNs was only weakly suppressed by endocannabinoids released by depolarized postsynaptic MSNs. The results show that the combined use of transgenic animals and paired-recording techniques allows the study of synaptic connections between rare neurons. Using these techniques, we showed that activation of CB(1) receptors on axon terminals of (i) PV-FSNs and (ii) MSNs leads to presynaptic inhibition of GABAergic synaptic transmission between these axons and their postsynaptic targets, the MSNs. The cannabinoids acted preferentially on axon terminals without effects on the somatodendritic region of the neurons.

p53-Mediated Apoptosis, Neuroglobin Overexpression, and Globin Deposits in a Patient With Hereditary Ferritinopathy

The apoptotic death of putaminal neurons and glia in a patient with hereditary ferritinopathy is studied immunohistochemically with antibodies to p53, activated caspase-3, PUMA, BAX, cytochrome c, and inducible nitric oxide synthase. In addition to the overexpression of ferritin and the iron accumulations assumed to result from the genetically incompetent ferritin molecule, additional contributions to the iron, heme, and hyaline deposits in this disease are sought with antibodies to 2 recently discovered globins in humans, neuroglobin and cytoglobin. The "pathognomonic" swollen to vacuolated nuclei are immunoreactive for both p53 and activated caspase-3, indicating the intervention of the p53-mediated apoptotic pathway. The immunohistochemical demonstration of neuroglobin in the swollen nuclei and both globins in the hyaline deposits highlights the potential pathogenic importance of 2 other iron-containing proteins in this disease that is largely restricted to brain. Hereditary ferritinopathy is the first human disease in which abnormalities in these heme-containing proteins are demonstrated.

[Blocks of neuron correlates of behaviour in the monkey brain prefrontal cortex and striatum]

The dynamics of tonic neuron activity of the putamen and prefrontal cortex of monkey's brain is researched by studying sequential stages of executive behavior program. It is determined that tonic responses in both structures are classified in separate blocks. The blocks are timed to key moments of behavior connected with intermediate goals framed by a common task. As to the structures of the aforesaid blocks of tonic activity in cortex and striatum, they are different in instructive part of the program and similar in executive one. More differential attitude of cortex is revealed to the sequence of executive behavior activity.

Differential regulation of ionotropic glutamate receptor subunits following cocaine self-administration

Previous examination of binge cocaine self-administration and 2 week withdrawal from cocaine self-administration on ionotropic glutamate receptor subunit (iGluRs) protein levels revealed significant alterations in iGluR protein levels that differed between the mesocorticolimbic and nigrostriatal pathways. The present study was undertaken to extend the examination of cocaine-induced alterations in iGluR protein expression by assessing the effects of acute withdrawal (15-16 h) from limited access cocaine self-administration (8 h/day, 15 days). Western blotting was used to compare levels of iGluR protein expression (NR1-3B, GluR1-7, KA2) in the mesolimbic (ventral tegmental area, VTA; nucleus accumbens, NAc; and prefrontal cortex, PFC) and nigrostriatal pathways (substantia nigra, SN and dorsal caudate-putamen, CPu). Within the mesolimbic pathway, reductions were observed in NR1 and GluR5 immunoreactivity in the VTA although no significant alterations were observed in any iGluR subunits in the NAc. In the PFC, NR1 was significantly upregulated while GluR2/3, GluR4, GluR5, GluR6/7, and KA2 were decreased. Within the nigrostriatal pathway, NR1, NR2A, NR2B, GluR1, GluR6/7 and KA2 were increased in the dorsal CPu, whereas no significant changes were observed in the SN. The results demonstrate region- and pathway-specific alterations in iGluR subunit expression following limited cocaine self-administration and suggest the importance for the activation of pathways that are substrates of the reinforcing and motoric effects of cocaine.

Comparison of population activity in the dorsal premotor cortex and putamen during the learning of arbitrary visuomotor mappings

A previous study found that as monkeys learned novel mappings between visual cues and responses, neuronal activity patterns evolved at approximately the same time in both the dorsal premotor cortex (PMd) and the putamen. Here we report that, in both regions, the population activity for novel mappings came to resemble that for familiar ones as learning progressed. Both regions showed activity differences on trials with correct responses versus those with incorrect ones. In addition to these common features, we observed two noteworthy differences between PMd and putamen activity during learning. After a response choice had been made, but prior to feedback about the correctness of that choice (reward or nonreward), the putamen showed a sustained activity increase in activity, whereas PMd did not. Also in the putamen, this prereward activity was highly selective for the specific visuomotor mapping that had just been performed, and this selectivity was maintained until the time of the reward. After performance reached an asymptote, the degree of this selectivity decreased markedly to the level typical for familiar visuomotor mappings. These findings support the hypothesis that neurons in the striatum play a pivotal role in associative learning.

The striatofugal fiber system in primates: a reevaluation of its organization based on single-axon tracing studies

The current model of basal ganglia rests on the idea that the striatofugal system is composed of two separate (direct and indirect) pathways originating from distinct cell populations in the striatum. The striatum itself is divided into two major compartments, the striosomes and the matrix, which differ by their neurochemical makeup and input/output connections. Here, neurons located in either striosomes or the extrastriosomal matrix in squirrel monkeys were injected with biotin dextran amine, and their labeled axons were entirely reconstructed with a camera lucida. Twenty-four of 27 reconstructed axons arborized into the three main striatal targets (external pallidum, globus pallidus, and substantia nigra pars reticulata), a finding that is at odds with the concept of a dual striatofugal system. Axons of striosomal neurons formed several columnar terminal fields in the substantia nigra pars reticulata. These data indicate that the substantia nigra pars compacta is neither the only nor the main target of striosomal neurons, a finding that calls for a reevaluation of the organization of the striatonigral projection system.

Different corticostriatal projections from two parts of the cortical masticatory area in the rabbit

The cortical masticatory area (CMA) elicits rhythmic jaw movements in response to repetitive stimulation and is involved in the control of mastication. Based on jaw movement patterns, the CMA is divided into two parts. One is the part of the CMA in which a T-pattern similar to jaw movements during food transport in natural mastication is evoked by electrical stimulation. The other is more dorsomedially located, and during chewing a C-pattern similar to jaw movements can be induced. However, it is still not known which region of the putamen receives projections from the CMA and whether projections originate from both parts of the CMA. In this study, electrophysiological and histological experiments were undertaken in rabbits to investigate projections from the CMA to the putamen. Both experiments showed that the ventral region of the putamen received projections from the CMA. The density of the projections from the CMA area inducing the T-pattern seemed to be higher than that from the area inducing the C-pattern. Furthermore, the peak latency of the evoked potentials from stimulation of the CMA area inducing the T-pattern was shorter than that from stimulation of the area inducing the C-pattern. The data obtained from the present study indicate the functional role of the ventral region of the putamen in the regulation of mastication, and further suggest that the corticostriatal pathway is involved in the transition between behavioral jaw movement patterns.

Tonically active neurons in the primate caudate nucleus and putamen differentially encode instructed motivational outcomes of action

To achieve a goal, animals procure immediately available rewards, escape from aversive events, or endure the absence of rewards. The neuronal substrates for these goal-directed actions include the limbic system and the basal ganglia. In the striatum, tonically active neurons (TANs), presumed cholinergic interneurons, were originally shown to respond to reward-associated stimuli and to evolve their activity through learning. Subsequent studies revealed that they also respond to aversive event-associated stimuli such as an airpuff on the face and that they are less selective to whether the stimuli instruct reward or no reward. To address this paradox, we designed a set of experiments in which macaque monkeys performed a set of visual reaction time tasks while expecting a reward, during escape from an aversive event, and in the absence of a reward. We found that TANs respond to instruction stimuli associated with motivational outcomes (312 of 390; 80%) but not to unassociated ones (51 of 390; 13%), and that they mostly differentiate associated instructions (217 of 312; 70%). We also found that a higher percentage of TANs in the caudate nucleus respond to stimuli associated with motivational outcomes (118 of 128; 92%) than in the putamen (194 of 262; 74%), whereas a higher percentage of TANs in the putamen respond to go signals for the lever release (112 of 262; 43%) than in the caudate nucleus (27 of 128; 21%), especially for an action expecting a reward. These findings suggest a distinct, pivotal role of TANs in the caudate nucleus and putamen in encoding instructed motivational contexts for goal-directed action planning and learning.

Differential expression of AMPA receptor subunits in substance P receptor-containing neurons of the caudate-putamen of rats

Previous evidence has suggested that glutamate-driving neurotransmission and glutamate-excitotoxicity are modulated by substance P in the basal ganglia, but the assembly of glutamate receptors mediating this process remains to be delineated. By using a double immunofluorescence, cellular expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor subunits (GluR1-4) in substance P receptor (SPR)-containing neurons was examined in the striatum of rats. It revealed that distribution of SPR-immunoreactive neurons completely overlapped with that of GluR1, 2, 3 or 4-immunoreactive neurons in the caudate-putamen. Neurons showing both SPR and AMPA receptor subunits (except of GluR3)-immunoreactivity were observed: all (100%) of SPR-positive neurons displayed GluR1-, GluR2- or GluR4-immunoreactivity, and the double-labeled neurons constituted about 33, 3 or 29% of total GluR-positive ones. In contrast, the neurons exhibiting both SPR- and GluR3-immunoreactivity were not detected, though numerous GluR3-positive neurons were still distributed in the caudate-putamen regions. Co-localization of SPR and distinct AMPA receptor subunits in the striatal neurons has provided a basis for functional modulation of neuronal APMA receptors by substance P in the caudate-putamen of rodents. Taken together with previous observations, this study has also suggested that, through interaction with AMPA receptors composed of subunits 1, 2 and 4, substance P or neurokinin peptides may play important roles in regulating neuronal properties and protecting neurons from excitotoxicity in the basal ganglia of mammals.

Sequential rearrangements of the ensemble activity of putamen neurons in the monkey brain as a correlate of continuous behavior

Simultaneous recordings were made of the spike activity of groups of 6-7 neurons in the putamen in two monkeys (Macaca nemestrina and Macaca mulatta) during performance of alternative spatial selection. Discriminant analysis was used to evaluate the magnitude of rearrangements in spike activity in groups of neurons during transitions from each step of the behavioral program to the next, along with the degree of differences in reactivity mosaics formed at each step in different versions of task execution. Rearrangements in spike activity were noted at all steps of the program. The dynamics of rearrangements on selection of the right and left feeders were different, leading to the appearance of significant differences in the reactivity mosaics at the decision-taking and reinforcement-receiving steps. The rearrangements preceding voluntary movement of one hand were more marked in the contralateral hemisphere. During performance of movements, the volume of rearrangements could increase, though differences in rearrangements accompanying movements of the right and left hands decreased. On receipt of reinforcement, rearrangements were greater when the animals selected a specified feeder (the left feeder) independently of which hemisphere was recorded.

Behavior-reactive neuron populations in the monkey neostriatum

Comparative analysis of neuron activity in the monkey putamen during multistep behavior showed that putamen neurons are active during all the animal's behavioral actions. The difference between the number of active neurons at a given step of the behavior as compared with the preceding step was found to be significantly smaller than the number of neurons reorganizing their activity at this step. Reorganization of neuron activity in the putamen is regarded as a reflection of the efferent code controlling the behavior, while the extent of reorganization is regarded as a measure of the change in this code in association with the organization of a sequential behavioral action. Changes in the numbers of active neurons at different stage of behavior and reorganization of their activity occurred independently of each other. This may be associated with the two afferent systems of the striatum: that ascending from the brainstem and the corticofugal, which carries differential information to the neural network of the striatum from various parts of the cortex.

The differentiating activity of monkey putamen neurons during performance of alternative spatial selection

Spike activity was recorded from three zones of the putamen in monkeys trained to bimanual operant activity during performance of an alternative spatial selection task. Neuron responses were analyzed using the following criteria: a) differentiation of the side providing reinforcement (differentiating/non-differentiating responses); b) response duration (tonic/phasic); c) response laterality (contralateral/ipsilateral hemispheres); d) baseline activity frequency. The differentiating activity of cells was found to show the closest correlation with behavioral aspects of the program, particularly the tonic part and, even more so, contralateral tonic responses. It is suggested that differentiating activity, as opposed to non-differentiating activity, is less a reflection of the morphological and neurochemical characteristics of the neural elements of the putamen than of their functional homogeneity in relation to external determinants of behavior.

Analysis of the morphological substrate for information processing in the striatum based on the organizational characteristics of its afferent projections

Retrograde axonal transport of markers was used to study the afferent projections arising from functionally diverse cortical and subcortical structures and running to various segments of the caudate nucleus, nucleus accumbens, and putamen of the dog brain. The characteristics of the spatial organization of these projections were used to analyze the morphological aspects of the segregated and convergent conduction and processing of information in the striatum which underlie striatal function.

Chronic treatment with atypical neuroleptics induces striosomal FosB/DeltaFosB expression in rats

BACKGROUND

Studies have shown that neuroleptics regulate expression of the transcription factor FosB/DeltaFosB in the striatum, including the accumbens and caudate-putamen; however, the striatum is also divided into another structural dimension, the striosome and matrix compartments. The precise distribution of FosB/DeltaFosB induced by chronic neuroleptics in these striatal compartments is poorly understood.

METHODS

Rats received either single acute injections or chronic injections of clozapine (0 or 20 mg/kg, intraperitoneally [IP]), olanzapine (0 or 5 mg/kg, IP), or haloperidol (0 or 1.5 mg/kg, IP) for 25 days. The levels and compartmental distribution of FosB/DeltaFosB were examined.

RESULTS

Chronic clozapine induced clustered FosB/DeltaFosB expression within striosomes of the caudate-putamen. This pattern was due to increased levels of FosB/DeltaFosB in striosomes within the ventrolateral caudate-putamen and reduced levels of basal FosB/DeltaFosB in the matrix in the entire caudate-putamen. In contrast, chronic haloperidol increased FosB/DeltaFosB equally within the matrix and striosomes throughout the entire caudate-putamen. Chronic olanzapine induced an intermediate pattern.

CONCLUSIONS

The relative absence of FosB/DeltaFosB expression in the matrix correlates with the lack of parkinsonism of atypical neuroleptics. Expression of FosB/DeltaFosB in the matrix may contribute to parkinsonism of typical neuroleptics.

Mesostriatal and mesolimbic projections of midbrain neurons immunoreactive for estrogen receptor beta or androgen receptors in rats

The dopamine (DA) inputs to the caudate putamen, the nucleus accumbens, and the amygdala in rats are sensitive to circulating estrogens and androgens. One mechanism for the hormone modulation of these systems may be via actions at cognate intracellular estrogen and androgen receptors. However, although it is known that specific subsets of midbrain DA neurons are immunopositive for estrogen receptor beta (ERbeta) or androgen receptors (ARs), it is not known where these receptor-bearing cells project. To address this issue, we combined double-label immunocytochemistry with retrograde tract tracing to identify the forebrain projections of ERbeta- or AR-immunoreactive (IR) midbrain neurons. Specifically, Fluoro-Gold and/or cholera toxin were injected into discrete subregions of the caudate-putamen, the nucleus accumbens, or the amygdala. Evaluations of the resultant midbrain labeling revealed that ERbeta-IR neurons sent collateral projections mainly to both the ventral caudate-putamen and the amygdala, but not to the dorsal caudate or nucleus accumbens. In contrast, AR-IR neurons projected either to the amygdala or the nucleus accumbens but not to the caudate-putamen. The organization of these forebrain projections concurs with some of the known hormone sensitivities of mesostriatal and mesolimbic DA systems in rats and provides an anatomical model that predicts separate influences for androgens and estrogens over mesostriatal and mesolimbic DA systems.

Responses of tonically active neurons in the monkey striatum discriminate between motivationally opposing stimuli

The striatum is involved in the control of appetitively motivated behavior. We found previously that tonically active neurons (TANs) in the monkey striatum show discriminative responses to different stimuli that are appetitive or aversive. However, these differential responses may reflect the sensory qualities of the stimulus rather than its motivational value. In the present study, we sought to define more precisely the relationship between the particular aspect of the response of TANs and the motivational value of stimuli. For this purpose, three monkeys were presented with two types of aversive stimuli (loud sound and air puff) and one appetitive stimulus (fruit juice). In most instances, the TAN responses to the loud sound and the air puff were similar, in terms of response pattern and duration, whereas responses to the liquid reward showed distinct features. Using classical appetitive conditioning, we reversed the motivational value of a stimulus so that a previously aversive stimulus was now associatively paired with a reward and found that this manipulation selectively modifies the expression of TAN responses to the stimulus. These data indicate that the characteristics of neuronal responses undergo modifications when the valence of the stimulus is changed from aversive to appetitive during associative learning, suggesting that TANs may contribute to a form of stimulus encoding that is dependent on motivational attributes. The adaptation of TAN responses such as observed in the present study likewise reflects a neuronal system that adjusts to the motivational information about environmental events.

NPY-mRNA expressions in the nucleus accumbens, caudate putamen and cerebral cortex of apomorphine-susceptible and apomorphine-unsusceptible rats

Using the apomorphine-induced stereotyped gnawing response as a selection criterion, two distinct groups of rats can be distinguished, apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats. These two lines differ in several components of both striatal and extrastriatal areas. This study deals with the expression of neuropeptide Y (NPY)mRNA-expressing neurons in the nucleus accumbens, caudate putamen and cerebral cortex of both rat lines, using non-radioactive in situ hybridisation. The morphology of the neurons in the three regions is similar, viz. oblong, rectangular or triangular, with two or three processes. The neurons are homogeneously distributed in all regions, and in the nucleus accumbens they are particularly numerous ventrally to the anterior commissure. Using automated image analysis, the mean numerical density of NPYmRNA-positive neurons per brain region and the mean NPYmRNA expression level per neuron per brain region were determined. No differences appear in the numerical densities of NPYmRNA-containing neurons in the nucleus accumbens, caudate putamen and cortex between APO-SUS and APO-UNSUS rats. However, distinct differences between the rat lines are present in the level of NPYmRNA expression per neuron in the nucleus accumbens and in the caudate putamen, showing that NPY contributes to the differential neurochemical make-up of these rat lines that is responsible for their obvious differences in behaviour, physiology and immune competence.

NADPH-diaphorase staining reveals new types of interneurons in human putamen

Neurons in the human striatum have been divided into five or seven different types, respectively. To further characterize these interneurons, we investigated the putamen of five brains by means of NADPH-diaphorase staining and compared our results to previous classifications in man. The NADPH-diaphorase method is selective for nitric oxide synthase (NOS); in the human striatum, predominantly interneurons were stained. NADPH-diaphorase positive neurons were then further examined. They showed clear morphological differences and could be classified into 12 different types, which only partially corresponded to previously described neuron types. Thus, we suggest at least three novel types of neostriatal interneurons. Furthermore, a special class of large neurons thought to be efferent in nature, stained NOS-positive.

Intraputamenal infusion of GDNF in aged rhesus monkeys: distribution and dopaminergic effects

Site-specific delivery of trophic factors in the brain may be important for achieving therapeutic efficacy without unwanted side effects. This study evaluated the site-specific infusion of glial cell line-derived neurotrophic factor (GDNF) into the right putamen of aged rhesus monkeys. After 4 weeks of continuous infusion at a rate of 22.5 microg/day, GDNF had diffused up to 11 mm from the catheter openings in the putamen into the rostral putamen, internal capsule, external capsule, caudate nucleus, and globus pallidus. Anisotropic flow along the external capsule tracts carried GDNF into the anterior amygdaloid area. Backflow of GDNF along the catheter track from the frontal cortex infiltrated juxtaposed corpus callosal and cortical tissue. GDNF was carried by retrograde transport to dopamine neurons in the ipsilateral substantia nigra, stimulating an 18% increase in the number of tyrosine hydroxylase (TH)-positive dopamine neurons and a 28% increase in dopamine neuron perikaryal size. Also, TH-positive fiber density was increased in the ipsilateral globus pallidus, caudate nucleus, and putamen. Anatomic effects from GDNF stimulation of the dopaminergic system were restricted to the ipsilateral hemisphere. Retrograde GDNF labeling was also present in a few TH-positive neurons in the locus coeruleus and a large cluster of TH-negative neurons in the ventral anterior thalamus. Anterograde transport of GDNF was evident in axons in the pyramidal tract from the cerebral peduncle to the caudal spinal cord. Tissue injury from the intraparenchymal catheter and continuous infusion was confined primarily to a narrow zone surrounding the track and was mild to moderate in severity.

The location of persistent amphetamine-induced changes in the density of dendritic spines on medium spiny neurons in the nucleus accumbens and caudate-putamen

Repeated intermittent treatment with amphetamine increases the density of dendritic spines on medium spiny neurons (MSNs) in the nucleus accumbens (NAcc). The purpose of this study was two-fold: (1) to determine whether amphetamine has similar effects on MSNs in the caudate-putamen (CPu) and (2) to determine if this effect is localized to distal dendrites, the site of convergence of dopamine (DA) and glutamate synapses in the striatum. An amphetamine treatment regimen that produced behavioral sensitization increased the density of dendritic spines on MSNs in both the NAcc and dorsolateral CPu. This effect was long lasting, because it was evident 3.5 months after the discontinuation of drug treatment. The increase in spine density was confined to distal dendrites of MSNs, and was not apparent on dendrites close to the cell body. It is concluded that amphetamine may preferentially reorganize synapses at the site of DA-glutamate interaction in the striatum, which may alter DA-glutamate signaling and thereby contribute to some of the persistent behavioral and psychological consequences of repeated exposure to psychostimulant drugs.

Putaminal activity for simple reactions or self-timed movements

To examine the role of basal ganglia-cortical circuits in movement initiation, we trained monkeys to make the same arm movements in two ways-in immediate reaction to a randomly timed external cue (cued movements) and also following a variable delay without an explicit initiation signal (self-timed movements). The two movement types were interleaved and balanced in overall timing to allow a direct comparison of activity before and during the movement. Posterior putaminal neurons generally had phasic, movement-related discharges that were comparable for cued and self-timed movements. On cued movements, neuronal activity increased sharply following cue onset. However, for self-timed movements, there was a slow build-up in activity that preceded the phasic discharge. This slow build-up was time-locked to movement and restricted to a narrow time window hundreds of milliseconds before movement. The difference in premovement activity between cued and self-timed trials was present before the earliest cue-onset times and was not related to any differences in the overall time-to-move between the two types of trials. These features suggest that activity evolving in the basal ganglia-cortical circuitry may drive the initiation of movements by increasing until an activity threshold is exceeded. The activity may increase abruptly in response to an external cue or gradually when the timing of movements is determined by the animals themselves rather than an external cue. In this view, small changes in activity that occur in advance of the much larger perimovement neuronal activity may be an important determinant of when movement occurs. In support of this hypothesis, we found that even for cued movements, faster reaction times were associated with slightly higher levels of activity hundreds of milliseconds before movement.

New component of the limbic system: Marginal division of the neostriatum that links the limbic system to the basal nucleus of Meynert

The limbic system refers to a group of connected neural regions that are associated with motivation, learning, and memory. The marginal division (MrD) is a zone located at the caudal border of the neostriatum in mammalian brains that has been shown to be involved in learning and memory. In a previous study, c-fos expression showed functional connections between the MrD, basal nucleus of Meynert (NBM) and limbic system (Shu et al., 1988a, 1999). In the present study, to explore the relationship between these regions, the expression of limbic system-associated membrane protein (LAMP) was investigated using molecular and immunohistochemical methods. Synaptic and functional connections between the MrD and the NBM were studied also using tract tracing, electron microscopic and behavioral methods. LAMP is thought to be a marker of the limbic system and expression of LAMP protein and mRNA was observed in both the MrD and the limbic system. From such results, it is concluded that the MrD is a new component of the limbic system. Fibers from the MrD were observed projecting and synapsing on cholinergic neurons of the NBM. As reduction of learning and memory was induced by lesioning the projection from the MrD to the NBM, it would seem that the MrD modulates the learning and memory function of the NBM. In conclusion, the results of these studies suggest that the MrD is a new component of the limbic system, and there are functional and structural connections between the MrD, NBM and limbic system. The MrD seems to act as a link between the limbic system and the NBM, and plays a role in learning and memory.

[Differentiating activity of monkey putamen neurons during performance of the alternative spatial choice]

Single unit activity was recorded in monkeys in three putamen zones learned a bimanual operant activity during performance of the task of alternative spatial choice. The neuronal reactions were specially analyzed by the criteria as follows: a) differentiation of the side of reward (differentiating--non-differentiating reactions); b) character of reaction by duration (tonic-phasic); c) laterality (contra- and ipsilateral reactions as related to hemisphere); d) frequency of background activity. It was shown that differentiating cell activity, especially their tonic part and in still greater degree contra-lateral tonic reactions most closely correlate with behavioral aspects of the program. The assumption that differentiating activity, unlike non-differentiating one, is the reflection of not only morphological and neurochemical characteristic features of nervous elements of putamen but of its functional uniformity in relation to external determinants of behavior, was put forward.

[Sequential rearrangements of ensemble activity of the putamen neurons of monkeys as a correlate to continuous behavior]

Simultaneous recording of unit activity of 6-8 putamen neurons in two monkeys (M. nemestrina and M. mulatta) during performance of the task of alternative spatial choice, was carried out. The extent of rearrangements of the activity in the groups of neurons with the transition from every step of the behavioral program to the next one and the degree of difference in mosaics of reactivity, forming at every step with a different variants of performance, were evaluated using discriminative analysis. The rearrangements of the impulse activity were recorded in all steps of the program. The dynamics of rearrangements with the choice of right or left feeder was different, which resulted in appearance of significant differences in mosaics of reactivity at the stage of decision making and receiving reward. The rearrangements preceding the task-oriented movement of one hand were more pronounced in the contralateral hemisphere. The volume of rearrangements may increase with the performance of movement but the differences of mosaics formed during the movement of right and left hand are decreasing. At the stage of reception of the reward, the rearrangements were greater in case the animal chose the certain (left) feeder irrespective of the side of recording the unit activity.

[Neurons of the human basal ganglia (striatum and basolateral amygdala) expressing the enzyme NADPH-d]

In human striatum and basolateral amygdala NADPH-d+ neurons were revealed (after Vincent et al., 1983); and in striatum strio-cortical neurons were also revealed using DiI marker (after Dahtstrom and Belichenko, 1995). The NADPH-d+ neurons were numerous in both formations. Staining of NADPH-d+ neurons with their processes, and our previous study of striatal and amygdalar human neurons by Golgi method made it possible to identify the species of neurons with their assessment as sparsely or densely branched. The main efferent neurons of striatum and basolateral amygdala (densely branched medium spiny and bushy spiny, respectively) and their densely branched interneurons were not marked. Efferent NADPH-d+ neurons included the most numerous ones in both formations. A projection of reticular striatal neurons to cortex was also shown. The NADPH-d+ interneurons belonged to sparsely branched forms. In striatum they included slender-dendritic and long-dendritic bipolars (numerous), ordinary bipolars, twisted and large poor-dendritic cells; in amygdala--the same bipolars and radial cells. Thus, the NADPH-d positive cells in the formations under study were represented by more "ancient" or less structurally complex cell forms.

[Populations of behavior-reactive neurons in the monkey neostriatum]

Comparative analysis of the unit activity of the monkey putamen during multistage behavior showed that neurons of the putamen are active during all the behavioral actions. It was established that the number of the behavior-related neurons changes considerably less than number of neurons which reorganize their activity at the time. Reorganization of unit activity in the putamen is considered as reflecting the efferent code which controls behavior, and the degree of reorganization--as a measure of change of this code in relation to organization of ongoing behavioral action. It has been discovered that the change in the number of the active neurons at various steps of behavior and reorganization of their activity occurs independently. It may be related to two main afferent systems of striatum: ascending from rhe brain stem, and corticofugal which brings differentiated information to the neuronal net of striatum from various parts of the cortex.

Organization of corticostriatal motor inputs in monkey putamen

To analyze the organization of corticostriatal motor inputs, we examined the neuronal responses in the putamen (Put) to stimulation in the primary motor cortex (MI) and the supplementary motor area (SMA). Stimulating electrodes were chronically implanted in the distal and proximal parts of the forelimb representation of the MI and in the forelimb representation of the SMA in Japanese monkeys (Macaca fuscata). Stimulation in the MI and SMA evoked orthodromic spike discharges in both phasically active and tonically active Put neurons. The latency of excitation evoked by MI stimulation was shorter than that of excitation evoked by SMA stimulation. Neurons responding exclusively to MI stimulation (MI-recipient neurons) and those responding exclusively to SMA stimulation (SMA-recipient neurons) were distributed predominantly in the ventrolateral and dorsomedial portion of the caudal aspect of the Put, respectively. About 20% of the recorded neurons responded concurrently to stimulation in both the MI and SMA (MI + SMA-recipient neurons). These neurons were located in the intermediate zone between the MI- and SMA-recipient zones. More than half of the Put neurons responded to sensorimotor stimulation. Movements of the forelimb were readily elicited by microstimulation in the MI-recipient zone, less frequently in the MI + SMA-recipient zone, and rarely in the SMA-recipient zone. More detailed analysis of the somatotopic arrangement based on cortical inputs, sensorimotor responses, and microstimulation-evoked movements revealed that within the MI- and MI + SMA-recipient zones of the Put, neurons representing the distal part of the forelimb were located more ventrally than those representing the proximal part. No such somatotopy was clearly detected in the SMA-recipient zone. The present results indicate that corticostriatal inputs from the forelimb regions of the MI and SMA are largely segregated. On the other hand, convergent inputs from the MI and SMA were noted on single neurons located at the junction between the two input zones. In addition, the corticostriatal inputs from the forelimb region of the MI exhibited a distal to proximal somatotopic organization along the ventrodorsal axis of the Put.

Delta FosB regulates wheel running

DeltaFosB is a transcription factor that accumulates in a region-specific manner in the brain after chronic perturbations. For example, repeated administration of drugs of abuse increases levels of DeltaFosB in the striatum. In the present study, we analyzed the effect of spontaneous wheel running, as a model for a natural rewarding behavior, on levels of DeltaFosB in striatal regions. Moreover, mice that inducibly overexpress DeltaFosB in specific subpopulations of striatal neurons were used to study the possible role of DeltaFosB on running behavior. Lewis rats given ad libitum access to running wheels for 30 d covered what would correspond to approximately 10 km/d and showed increased levels of DeltaFosB in the nucleus accumbens compared with rats exposed to locked running wheels. Mice that overexpress DeltaFosB selectively in striatal dynorphin-containing neurons increased their daily running compared with control littermates, whereas mice that overexpress DeltaFosB predominantly in striatal enkephalin-containing neurons ran considerably less than controls. Data from the present study demonstrate that like drugs of abuse, voluntary running increases levels of DeltaFosB in brain reward pathways. Furthermore, overexpression of DeltaFosB in a distinct striatal output neuronal population increases running behavior. Because previous work has shown that DeltaFosB overexpression within this same neuronal population increases the rewarding properties of drugs of abuse, results of the present study suggest that DeltaFosB may play a key role in controlling both natural and drug-induced reward.

Proliferating cells can differentiate into neurons in the striatum of normal adult monkey

In this study we used bromodeoxyuridine (BrdU), a thymidine analogue that is incorporated into the DNA of mitotic cells, to study the cytogenesis status of the striatum in normal, adult, squirrel monkeys (Saimiri sciureus). Three weeks following BrdU injection, numerous BrdU-labeled (+) cells were encountered within both the dorsal and the ventral striatum, including the nucleus accumbens. Their number ranged from 5 to 50 per 40 microm-thick section. These BrdU+ cells were more abundant medially than laterally and displayed a rostrocaudal-decreasing gradient in the caudate nucleus and putamen. Double-immunofluorescence confocal studies have revealed that about 5-10% of the BrdU+ striatal cells expressed the neuronal nuclear antigen (NeuN), a marker for mature neurons. These findings suggest that new neurons are produced throughout adult life in the striatum of normal, adult primates. This result raises the possibility of experimentally enhancing the recruitment of these newborn neurons as a means to alleviate the symptoms of neurodegenerative diseases that affect the striatum.

Long-term effects of olanzapine, risperidone, and quetiapine on serotonin 1A, 2A and 2C receptors in rat forebrain regions

RATIONALE

Serotonin (5-HT) and its receptors have been implicated in various neuropsychiatric disorders. Altered serotonergic neurotransmission and interactions between 5-HT and dopamine (DA) systems may contribute to the pathophysiology of idiopathic psychotic or manic disorders. Interactions with 5-HT receptors may also contribute to special properties of modern antipsychotic drugs not yet evaluated for long-term effects on 5-HT receptors.

OBJECTIVE AND METHODS

We surveyed effects of newer atypical antipsychotics on 5-HT receptor types 1A, 2A, and 2C in rat forebrain regions by quantitative receptor autoradiography with selective radioligands following 28 days of continuous infusion of drugs or control vehicle.

RESULTS

Infusion of olanzapine, risperidone, and quetiapine increased 1A, but decreased 2A receptor labeling in frontal cerebral cortex. Olanzapine decreased binding at 2C receptors in hippocampal CA(1) and CA(3) regions and perhaps entorhinal cortex; olanzapine, but neither risperidone nor quetiapine, also decreased 2C labeling in caudate-putamen.

CONCLUSIONS

The findings suggest that altered 5-HT(1A) and 5-HT(2A)receptor levels in frontal cortex, and 5-HT(2C) receptors in other forebrain regions, may contribute to psychopharmacological properties of these novel atypical antipsychotic agents, perhaps including their antipsychotic or antimanic actions, and low risk of adverse extrapyramidal effects.

Augmented motor activity and reduced striatal preprodynorphin mRNA induction in response to acute amphetamine administration in metabotropic glutamate receptor 1 knockout mice

Metabotropic glutamate receptor 1 (mGluR1) is a G-protein-coupled receptor and is expressed in the medium spiny projection neurons of mouse striatum. To define the role of mGluR1 in actions of psychostimulant, we compared both motor behavior and striatal neuropeptide mRNA expression between mGluR1 mutant and wild-type control mice after a single injection of amphetamine. We found that acute amphetamine injection increased motor activity in both mutant and control mice in a dose-dependent manner (1, 4, and 12 mg/kg, i.p.). However, the overall motor responses of mGluR1 -/- mice to all three doses of amphetamine were significantly greater than those of wild-type +/+ mice. Amphetamine also induced a dose-dependent elevation of preprodynorphin mRNA in the dorsal and ventral striatum of mutant and wild-type mice as revealed by quantitative in situ hybridization. In contrast to behavioral responses, the induction of dynorphin mRNA in both the dorsal and ventral striatum of mutant mice was significantly less than that of wild-type mice in response to the two higher doses of amphetamine. In addition, amphetamine elevated basal levels of substance P mRNA in the dorsal and ventral striatum of mGluR1 mutant mice to a similar level as that of wild-type mice. There were no differences in basal levels and distribution patterns of the two mRNAs between the two genotypes of mice treated with saline. These results demonstrate a clear augmented behavioral response of mGluR1 knockout mice to acute amphetamine exposure that is closely correlated with reduced dynorphin mRNA induction in the same mice. It appears that an intact mGluR1 is specifically critical for full dynorphin induction, and impaired mobilization of inhibitory dynorphin system as a result of lacking mGluR1 may contribute to an augmentation of motor stimulation in response to acute administration of psychostimulant.

A device for stereotactic transection of fiber bundles in rats

We have designed a device for stereotactic transection of fiber bundles in experiments using rats. Here, we present our assessment of its features relative to those of conventional methods. The instrument consists of a stainless steel cannula and a thin inner wire with a hook at one end and a hilt at the other. The hook can be extended or withdrawn freely by pushing or pulling the hilt. Lesions were evaluated in 12 male Wistar rats, after two targets, the anterior commissure (n=6) and the caudate-putamen (n=6), were transected. After the cannula was introduced into the target, the inner hook was extended in an anterior direction orthogonally to the transverse plane. Next, the entire device was pulled back along the insertion path to transect the neuronal fibers. Then the inner hook was withdrawn into the cannula and the entire device was removed. Seven days later, brains were removed for histologic processing. Microscopic examination demonstrated a slit like gap produced by transection at the target; the lesions were infiltrated by microglia and surrounded by gliosis. Adjacent regions were minimally damaged. The path of the cannula demonstrated only minimal gliosis. Unlike conventional methods, this device permits precise transection of deep fiber bundles with minimal damage to surrounding brain tissue.

Prion protein devoid of the octapeptide repeat region restores susceptibility to scrapie in PrP knockout mice

Mice devoid of PrP are resistant to scrapie and fail to replicate the agent. Introduction of transgenes expressing PrP into such mice restores susceptibility to scrapie. We find that truncated PrP devoid of the five copper binding octarepeats still sustains scrapie infection; however, incubation times are longer and prion titers and protease-resistant PrP are about 30-fold lower than in wild-type mice. Surprisingly, brains of terminally ill animals show no histopathology typical for scrapie. However, in the spinal cord, infectivity, gliosis, and motor neuron loss are as in scrapie-infected wild-type controls. Thus, while the region comprising the octarepeats is not essential for mediating pathogenesis and prion replication, it modulates the extent of these events and of disease presentation.

In vivo spectrometric calcium flux recordings of intrinsic Caudate-Putamen cells and transplanted IMR-32 neuroblastoma cells using miniature fiber optrodes in anesthetized and awake rats and monkeys

A method is described to enable the recording of transient intracellular calcium changes in deep brain structures in anesthetized and awake animals using a fluorescent indicator combined with in vivo optical detection methods. Optrodes were fabricated using a bifurcated fiber-optic cable with an attached infusion guide cannula. After intracranial implantation of an optrode, animals were prepared in the following manner, (1) rats (intra-striatal) and monkeys (intra-putamen) were infused with the fluorescent calcium indicator, Oregon Green, to load intrinsic cells; or (2) rats were intra-striatally transplanted with a slurry of dye-loaded IMR-32 neuroblastoma cells via pipette ejection. Excitation light from an argon-ion laser was launched through the optrode and passed into the tissue. The resulting calcium-induced fluorescence signals were captured by the optrode, then detected and processed by externalized photomultiplier- and CCD-based spectrometer electronics. In approximately 25% of all intrinsic cell recordings, the baseline fluorescence intensity was relatively stable over time whereas in the remainder, large amplitude oscillations were observed with a frequency in the range of 0.5-2 Hz. These Ca(2+) transients were inhibited by local infusion of 10 microM omega-conotoxin MVIIC and 1 microM TTX. Extracellular electrophysiological recordings that were made adjacent to the optrode tip revealed that the Ca(2+) oscillations were in phase with the burst firing of striatal neurons. This suggested that the optical signals had a neuronal origin, most likely from medium spiny neurons. Baseline fluorescence intensity increased during infusion of high [K(+)](o), the calcium ionophore, A-23187, or during temporary bilateral carotid artery occlusion. Monkey (Saimiri sciureus) putamen recordings also affirmed the presence of similar calcium-related transients in a non-human primate. In the transplant preparations, the IMR-32 cells displayed a stable, non-oscillating baseline fluorescence. They were similarly responsive to high [K(+)](o) challenge and appeared viable for at least several hours. Similar optical recording approaches might be applied to monitor other fluorescent, chemiluminescent or bioluminescent events from almost any brain structure. Moreover, transplanted transfected cells expressing a single specific receptor or ion-channel protein may effectively serve as biosensing elements for the measurement of extracellular neurochemical signaling.

Extracellular dopamine dynamics in rat caudate-putamen during experimenter-delivered and intracranial self-stimulation

Intracranial self-stimulation is an operant behavior whereby animals are conditioned to press a lever in order to receive an electrical stimulation of their dopamine neurons. This paradigm is thought to stimulate brain reward pathways and, as such, has been used to clarify the role of dopamine in reward. Striatal extracellular dopamine concentrations were monitored during the acquisition and maintenance of self-stimulation and compared to dopamine release generated by experimenter-delivered and yoked stimulation. Fast-scan cyclic voltammetry in conjunction with carbon-fiber microelectrodes was used to monitor evoked dopamine release in the caudate-putamen during electrical stimulation of the substantia nigra/ventral tegmental area. The sub-second temporal resolution of fast-scan cyclic voltammetry coupled with the micron spatial resolution of the microelectrodes allowed for the measurement of dopamine neurotransmission in real-time. Single experimenter-delivered stimulations, identical to those used during self-stimulation, evoked dopamine release in the caudate-putamen both before and after the self-stimulation sessions. Likewise, yoked stimulations of the substantia nigra/ventral tegmental area delivered to animals untrained to perform self-stimulation resulted in an increase in extracellular dopamine levels. During training sessions, experimenter-delivered stimulations evoked dopamine release. However, as the animals began lever-pressing, extracellular dopamine levels subsequently declined. Taken together, these results suggest that dopamine functions as an alerting device, wherein increases in extracellular dopamine are obtained by unpredicted or novel rewarding stimuli, but not by those which can be anticipated.

The types of neurones in the neostriatum of the guinea pig (Cavia porcellus): Golgi and Klüver-Barrera studies

The Golgi technique stain was used to reveal the cellular structure of the neostriatum (nucleus caudatus and putamen) in the guinea pig. The computerised reconstructions were made from Golgi impregnated neurones. On the basis of various criteria, 4 types of neurones were distinguished in the guinea pig neostriatum: 1. The rounded neurones (most numerous) with 5-8 thin dendritic trunks; 2. The triangular nerve cells with 3 thick dendritic trunks; 3. Two types of multipolar neurones differing in dendritic arborization pattern with 4-6 and 7-9 primary dendrites, respectively. 4. The pear-shaped cells, which divide into two distinctly different subpopulations.

Time-course of methamphetamine-induced neurotoxicity in rat caudate-putamen after single-dose treatment

The time-course of monoamine and tyrosine hydroxylase depletion after single-dose administration of D-methamphetamine (40 mg/kg s.c.) was investigated in caudate-putamen of male Sprague-Dawley rats. Times evaluated were 6, 12, 48, 72 and 240 h following treatment. Tyrosine hydroxylase was significantly reduced by 29, 60, 66, 76 and 76% of control at each of the respective post-treatment time intervals. Dopamine was not reduced 6 h following treatment. Dopamine was significantly reduced by 53, 57, 68 and 74% 12, 48, 72 and 240 h post-treatment, respectively. Reductions in caudate-putamen serotonin began earlier and were ultimately larger than for dopamine, with significant reductions of 28, 33 55, 74 and 81% at each of the respective post-treatment intervals. Confirmation of neurotoxicity was provided by measurement of glial fibrillary acidic protein (GFAP) 240 h post-treatment. GFAP was increased at this time interval by 150% above control. Methamphetamine-induced hyperthermia during the 6 h immediately after treatment was comparable among the groups of animals used for analyses at each time interval. The results demonstrate that methamphetamine-induced monoamine reductions in the caudate-putamen occur rapidly, peak at 75-80% below controls, and last for at least 10 days after a single dose. These effects are as large or larger than those reported after the commonly used 10 mg/kgx4 dose treatment regimen administered at 2-h intervals and provides an alternate model for the investigation of methamphetamine-induced neurotoxicity.

Strychnine-sensitive glycine receptors in rat caudatoputamen are expressed by cholinergic interneurons

Strychnine-sensitive glycine receptors are ligand-gated anion channels widely expressed in spinal cord and brainstem. Recent functional studies demonstrating glycine-induced release of [(3)H]acetylcholine in rat caudatoputamen suggested the existence of excitatory glycine receptors in that region. Since the expression of glycine receptors in the caudatoputamen had not been reported earlier, we studied the glycine receptor-like immunoreactivity in this structure using a monoclonal antibody (mAb4a) recognizing an epitope common to all of the ligand-binding alpha-subunit variants of the glycine receptor. [Becker et al. (1993) Brain Res. 11, 327-333; Nicola et al. (1992) Neurosci. Lett. 138, 173-178]. Immunohistochemistry with mAb4a disclosed a specific staining of sparsely distributed large neurons in rat caudatoputamen, displaying an immunoreactive signal of lower intensity than that observed in motoneurons in spinal cord. Fluorescent dual labelling demonstrated that glycine receptor-like immunoreactivity co-localizes with choline acetyltransferase-like immunoreactivity in rat caudatoputamen. All neurons with glycine receptor-like immunoreactivity in the caudatoputamen studied were immunoreactive with choline acetyltransferase, and represented a subpopulation of cholinergic neurons (approximately 90% of the somata with choline acetyltransferase-like immunoreactivity). These results suggest that strychnine-sensitive glycine receptors are present on cholinergic interneurons in rat caudatoputamen, supporting the hypothesis that glycine receptors inducing striatal release of [(3)H]acetylcholine may be localized to cholinergic neurons.

Topologic distribution of different types of neurons in the human putamen

OBJECTIVE

To test the assumption that the various types of neuron in the human putamen appear to be randomly distributed and to quantify the way in which they are arranged, stochastic geometry, multivariate analysis and the interactive evaluation technique were employed.

STUDY DESIGN

Twenty-seven human putamina without demonstrable signs of neurologic change were dissected out, fixed in 4% formalin and embedded in paraffin. The 20-micron paraffin sections were stained in an aldehyde-fuchsin and cresyl-violet solution, which makes it possible to distinguish between seven different neuron populations in the putamen. The gravity centers, size and form factors of these neurons were determined morphometrically under a light microscope. The data obtained were used to calculate the spatial distribution of the neurons by interactive and structure analytical methods.

RESULTS

Visual point field analysis revealed an irregular arrangement of the different types of neurons. Point process analysis detected a significant hard core process of type 1 and a cluster process of type 6 neurons. With nearest neighborhood analysis, significant differences were found between certain populations of neurons and Poisson processes. Comparison of the results of multivariate cluster analysis with the investigator-dependent results of visual point field analysis showed clear differences.

CONCLUSION

By means of structure analytical methods, the arrangement of different populations of neurons can be demonstrated. Some neuronal distributions are detectable only by using one of these techniques. The question of random or nonrandom distribution of the neurons in the human putamen can now be answered definitively: arrangement of the different populations of neurons is structured.

Preliminary findings of antistreptococcal antibody titers and basal ganglia volumes in tic, obsessive-compulsive, and attention deficit/hyperactivity disorders

BACKGROUND

Previous studies have provided preliminary serological evidence supporting the theory that symptoms of tic disorders or obsessive-compulsive disorder (OCD) may be sequelae of prior streptococcal infection. It is unclear, however, whether previously reported associations with streptococcal infection were obscured by the presence of diagnostic comorbidities. It is also unknown whether streptococcal infection is associated in vivo with anatomical alterations of the brain structures that have been implicated in the pathophysiology of these disorders.

METHODS

Antistreptococcal antibody titers were measured in 105 people diagnosed as having CTD, OCD, or attention-deficit/hyperactivity disorder (ADHD) and in 37 community controls without a disorder. Subjects were unselected with regard to their history of streptococcal exposure. Basal ganglia volumes were measured in 113 of these subjects (79 patients and 34 controls).

RESULTS

A DSM-IV diagnosis of ADHD was associated significantly with titers of 2 distinct antistreptococcal antibodies, antistreptolysin O and anti-deoxyribonuclease B. These associations remained significant after controlling for the effects of CTD and OCD comorbidity. No significant association was seen between antibody titers and a diagnosis of either CTD or OCD. When basal ganglia volumes were included in these analyses, the relationships between antibody titers and basal ganglia volumes were significantly different in OCD and ADHD subjects compared with other diagnostic groups. Higher antibody titers in these subjects were associated with larger volumes of the putamen and globus pallidus nuclei.

CONCLUSIONS

These findings suggest that the prior reports of an association between antistreptococcal antibodies and either CTD or OCD may have been confounded by the presence of ADHD. They also support the hypothesis that in susceptible persons who have ADHD or OCD, chronic or recurrent streptococcal infections are associated with structural alterations in basal ganglia nuclei.

Percentage incidence of gamma-aminobutyric acid neurons in the claustrum of the rabbit and comparison with the cortex and putamen

We describe the incidence of gamma-aminobutyric acid (GABA)ergic neurons after post-embedding immunocytochemistry on semithin sections of the claustrum, putamen and lateral, dorsal and medial cortical areas. Twelve percent of the neurons counted in the claustrum of 11 rabbits were GABAergic. This incidence was significantly higher in the dorsal halves of both the insular and endopiriform claustra than in the ventral (13 vs. 10%). The incidence of GABAergic cells was 4% in the putamen, 14% in the insular cortex, 15% in areas 17 and 18 and 13% in area 29d. Thus, our results indicate that in contrast to the putamen the incidence of GABAergic cells was similar in the claustrum and cortical areas. We interpret this in the light of the pallial origin of the claustrum, which has recently been substantiated.

The core-shell dichotomy of nucleus accumbens in the rhesus monkey as revealed by double-immunofluorescence and morphology of cholinergic interneurons

Double-immunolabelling experiments for the combinations, calretinin (CR)-calbindin, CR-tyrosine hydroxylase (TH) and calbindin-TH, were performed in rhesus monkeys to compare the chemical organization of the nucleus accumbens (ACC) in primates and rodents. Additionally, the soma sizes and numbers of primary dendrites of cholinergic neurons in the subregions of ACC were compared with those of caudate-putamen. Our findings subserve the shell-core concept also in the primate ACC, as like in the rat, CR immunoreactivity (-ir) due to intense neuropil labelling is very strong in the shell of rhesus monkey, but poor in the core. The staining intensity of this marker decreases in dorsoventral direction. An almost complementary pattern was noted in sections of the monkey ACC immunostained for both calbindin and TH. The cholinergic interneurons of the nucleus caudatus-putamen are clearly distinguished from those of the ACC and insula Calleja magna by their much bigger soma sizes and higher numbers of primary dendrites. Cholinergic neurons of the shell were found to be slightly, but significantly, larger than those of the core that also subserves subdivision of the primate ACC into shell and core. A low proportion of tyrosine-hydroxylase-immunostained cells, already previously described below the rostral ACC, co-expressed CR but not calbindin. A CR-immunoreactive neuronal population, intermingled with these cells, extends as a stripe medially to the ACC along the septal part of corpus callosum into the lateral septal area. The presumed origin of CR-immunoreactive fibres in the shell of ACC is discussed.

Studies of the functional characteristics of central neurons of the brain in a behavioral experiment

The activity of central integrative brain neurons is associated with the overall assessment of functionally diverse signals of different sensory modalities which converge on these neurons via parallel inputs. Processing this information, these neurons take part in organizing the animal's various actions and in the mechanisms involved in switching from one action to another. Therefore, understanding of the functional characteristics of central brain neurons requires studies in which the dynamics of neuron activity are recorded continuously throughout a sequence of actions performed by an animal. Traditional methods of analyzing neuron activity, such as the construction of post- and peristimulus histograms and cross-correlation analysis, are inadequate for this purpose. These methods allow analysis to be applied to neuron spike activity only around each synchronization point Their use for studies of a developed program of animal actions unavoidably leads to a set of separate histograms providing no information on the dynamics of neuron activity corresponding to continuous behavior. A complex approach to studying the neuronal correlates of behavior is suggested, designed to overcome these difficulties. The method is based on the use of a developed behavioral program with recording of several neurons in parallel, with analysis of neuron activity using a relative time scale based on the duration of each sequentially performed action. Non-traditional methods of processing neuron spike activity were developed for analysis of the resulting data, including construction of relative histograms and multidimensional statistics methods. These approaches allowed us to study the dynamics of neuron activity continuously through all the stages of performance of a behavioral program and obtain data on the involvement of each group of those neurons which were studied in functionally different actions. This methodology was tested using studies of the functional characteristics of striatum neurons in monkeys. Comparable data were obtained on the individual responses of neurons and on the dynamics of their activity at different stages of the animals' performance of a multicomponent behavioral program. This revealed the lack of functional specialization in striatum neurons and different patterns of their involvement in motor and cognitive functions.