Cells expressing preproenkephalin mRNA in the rat pineal gland are not serotonin-producing pinealocytes: evidence using in situ hybridization combined with immunocytochemistry for serotonin

1. Preproenkephalin (PPEnk) mRNA expressing cells have been identified in rat pineal gland using radioactive in situ hybridization histochemistry. 2. Approximately 7% of the cells in the pineal gland (7.5 +/- 0.86, mean +/- 95% CI) express PPEnk mRNA. These cells are distributed throughout the pineal as either scattered single cells or small groups of cells with large round or oval nuclei. 3. Using in situ hybridization combined with ABC immunocytochemistry for serotonin (5-HT) in the same pineal sections, the PPEnk mRNA labeling cells are found not to be serotonin-immunoreactive cells. These data indicate that the PPEnk mRNA is expressed in a certain discrete subpopulation of cells in the rat pineal gland and these cells are not serotonin-producing pinealocytes. 4. The physiologic role of PPEnk-derived peptides in the pineal remains unknown. It is possible that these peptides either are synthesized and secreted as hormones or act as pineal paracrine signals.

[The organization of the cortical projection system of the putamen in dogs]

Organization of cortical projections in dorsal and ventral segments of putamen rostral and caudal regions was studied in dogs using retrograde axonal transport of horse radish peroxidase. Dorsal region was shown to receive projections from neo- and mesocortex, while ventral is linked with all cortical units: neo-, meso- and allocortex. Dorsal part of putamen is to greater extent connected with cortical fields, relating to motor aspects of behavior (motor, premotor and somatosensory). Ventral region basically receives projections from the so called limbic cortical fields (cingular, insulary, orbital, periamygdalary and perirhinal). However, results of the present study do not allow to conclude on absolute division of projections of functionally different systems and only indicate the prevalence of one of them in certain topographic zone of the structure studied, i.e. elements of distinctive topography. consisting in presence of dorsal motor and ventral limbic morpho-functional regions are characteristic for dog putamen. No diversities in distribution of cortical projectional fibres along rostrocaudal axis of the structure were revealed. Initial neurons, projecting in putamen are of multilaminary localisation in the cortex.

Quantitative investigations into the histostructural nature of the human putamen. II. The differentiated topological distribution of certain neuron type arrangements

Several mathematical procedures have been worked out for describing quantitative arrangements of neurons, and especially subpopulations of neurons, in the human putamen. Visual point field analysis is a newly developed method for the qualitative recognition of the fuzzy clustering of types of neurons. Nearest neighbourhood analysis is an established procedure in stochastic geometry and image analysis. These cluster-analytical methods make possible the determination of local neuron topology. They represent an extension and application of the point pattern analysis (Diggle 1983), and are used here to calculate the statistical significance of certain arrangements of cells. The application of all these methods together revealed an interesting neuronal arrangement: type 1 neurons tend to remain at a certain distance from other type 1 neurons, whereas type 6 neurons lie close together.

Dopamine-modulated potassium channels on rat striatal neurons: specific activation and cellular expression

We have used cell-attached patch-clamp electrophysiology to characterize the activation and distribution of an 85 pS K+ channel on freshly dissociated rat striatal (caudate-putamen) neurons. In recordings from 643 cells, openings of this channel showed an absolute dependence on the presence of dopamine or the D2-like dopamine receptor agonist quinpirole in the cell-attached patch pipette, but were never seen when the D2 antagonist domperidone was applied along with quinpirole, or in the absence of drug. This channel displayed inward rectification at depolarized membrane potentials, but its activation was otherwise voltage insensitive. It was largely restricted to a subset of dissociated cells with diameters > or = 10 microns, with channel openings seen in about 25% of patches. When present, there were typically multiple channels per patch. Cells of this size were immunocytochemically stained for neuron-specific enolase but not glial fibrillary acidic protein; about 40% were also labeled for gamma-amino butyric acid (GABA) and about 60% for NADPH diaphorase, with GABAergic cells displaying a shape most similar to that of cells expressing the channel. A large number of distinct types of other channels were also present, comprising inwardly rectifying channels of 5-35 pS conductance and voltage-activated channels of 100-250 pS, but the frequencies of occurrence and fractional open times of these channels were independent of the presence or absence of dopaminergic agonists. Thus, the 85 pS K+ channel uniquely requires activation by a D2-like dopamine receptor on rat striatal neurons, and is selectively expressed by a subset of these cells, which are most likely to be GABAergic neurons.

Inhibitory effects of dopamine and methylenedioxymethamphetamine (MDMA) on glutamate-evoked firing of nucleus accumbens and caudate/putamen cells are enhanced following cocaine self-administration

Rats were allowed to self-administer cocaine during a 3-h session for 15 days. One to 11 days after the last cocaine exposure, rats were anesthetized with urethane and effects of microiontophoretically-applied dopamine on glutamate-evoked firing of neurons in the nucleus accumbens and in the caudate/putamen were tested. Dopamine produced a dose-dependent inhibition of glutamate-evoked firing in both the nucleus accumbens and the caudate/putamen of rats that had been repeatedly exposed to self-administered cocaine and in control rats. However, the DA-induced inhibition was significantly greater in the group that had self-administered cocaine. The cocaine self-administration group was significantly sensitized to the inhibitory effects of dopamine in both early (1-3 day) and later (9-11 days) periods of cocaine abstinence. Following cessation of repeated cocaine self-administration sessions, nucleus accumbens cells were also sensitized to the inhibitory effects of methylenedioxymethamphetamine (MDMA), a drug that increases extracellular levels of DA and serotonin in the nucleus accumbens. This sensitization to DA- and MDMA-induced inhibition in the nucleus accumbens and in the striatum indicates that long-term neuroadaptations occur in these regions of the nervous system following repeated exposure to self-administered cocaine.

Neuronal activity of primate putamen during categorical perception of somaesthetic stimuli

We have studied neuronal activity in the putamen of two monkeys trained to discriminate the speed of moving tactile stimuli. Animals pressed one of two target switches to indicate whether the speed of the probe across the skin was low or high. The activity of single neurones was recorded in the putamen ipsilateral to the glabrous skin of the stimulated hand and contralateral to the responding arm. During the task, we recorded neurones in the putamen that showed responses confined exclusively to the stimulus period of all speeds. A second class of putamen neurones responded during the stimulus period but continued discharging during the reaction and movement time period. None of these two classes of putamen neurones discharged when the same set of stimuli were delivered passively. A third class of putamen neurones responded differentially in the discrimination task and predicted whether the speed of the stimulus was low or high. A number of these neurones, which responded differentially during the categorization task, were tested in a light instruction task. This tested the possibility that these differential responses were associated with the intention to move the arm to one of the two target switches. Few neurones responded in this situation. These results indicate that the putamen, in addition to its role in motor regulation, is also involved in higher order aspects of sensory-motor behaviour and in the sensory decision process in this learned somaesthetic task.

Quantitative investigations into the histostructural nature of the human putamen. I. Staining, cell classification and morphometry

Combined staining with aldehyde and cresyl violet allows a reliable morphological distinction to be made between seven different types of neurons in the human putamen. We examined the age distribution of nearly 42,000 neurons in 27 normal putamina, using a semiautomatic morphometric procedure on defined tissue blocks. For morphometric evaluation and stereological calculations a section thickness of 20 microns is recommended. We modified routine aldehyde fuchsin cresyl violet combination staining for nervous tissue, since Braak's original method (Braak 1978, 1980) was developed for thick sections. The results show that neuronal density varies with age for the different types of neurons.

Dynamics of 5-hydroxytryptamine released from dopamine neurons in the caudate putamen of the rat

Fast-scan cyclic voltammetry has been used for the detection of 5-hydroxytryptamine (5-HT) in vivo. The applied potential waveform was previously optimized to maximize response times to concentration changes. This technique has been used to reinvestigate 5-HT release from striatal dopaminergic terminals after pharmacological pretreatment as reported by Stamford et al. [13]. Our results concur with those set forth by Stamford and further show that the dopamine transporter is responsible for 5-HT uptake in this experiment.

Assessment of neuronal density in the putamen in human immunodeficiency virus (HIV) infection. Application of stereology and spatial analysis of quadrats

Human immunodeficiency virus causes neuronal loss in various brain regions, but it has not been reported in the putamen. However, decrease in the volume of the putamen has been observed by magnetic resonance imaging. In order to clarify this issue two complementary methods; the stereological probe, the disector, and spatial analysis of quadrats, were applied in nondemented individuals who had died of acquired immune deficiency syndrome. A 21% decrease in neuronal density was observed in the human immunodeficiency virus group, especially those cases with human immunodeficiency virus encephalitis; however the statistical significance of this finding was borderline.

Immunocytochemical localization of mu-opioid receptor in the rat caudate-putamen

A guinea pig antibody against a C-terminal peptide of rat mu-opioid receptor (MOR) was produced to examine the distribution of MOR in the rat caudate-putamen (CP). The anti-peptide antibody recognized a protein of M(r) 69,000 in Triton X-100 extract of rat brain and in the membrane fraction of MOR-expressing culture cells. Intense MOR-like immunoreactivity (LI) was observed in island-like areas of the CP. Some MOR-LI was located on the cell bodies and dendrites of CP neurons. Double immunofluorescence study revealed that the intensely MOR-immunoreactive areas showed weak calbindin-LI, surrounded by intensely calbindin-positive regions. The results indicate that MOR-LI is enriched in the 'patches' of the neostriatal mosaic compartmentation.

Topographic distributions of monoamine oxidase-B-containing neurons in the mouse striatum

We have recently documented the presence of cholinergic neurons containing monoamine oxidase (MAO)-B activity in the striatum of C57BL/6 mouse. In the present study, we have mapped the topographical distributions of MAO-containing neurons in the mouse striatum. Positive neurons were located in the striatum of the entire rostralcaudal extent. However, the distribution of MAO-containing neurons was not uniform in the striatum. The larger number of positive neurons were located in the dorsal region of the C57BL/6 mouse striatum, in contrast to the uniform distributions of choline acetyltransferase-immunoreactive neurons in the mouse striatum. The present results suggest that cholinergic neurons are functionally heterogenous in the mouse striatum.

Colocalization of prosomatostatin-derived peptides in the caudate-putamen of the rat

In the striatum of rat, somatostatin 14, somatostatin 28, and somatostatin 28(1-12) have previously been localized within a small population of medium aspiny local circuit neurons. Because all three peptide fragments are generated through the cleavage of prosomatostatin by different converting enzymes, the possibility for differential expression of these peptides exists. In order to investigate this possibility, frozen sections were collected from the brains of adult female Wistar rats fixed with 4% paraformaldehyde and double labelled using immunocytochemistry and in situ hybridization. Sections were first processed for somatostatin 14, somatostatin 28, or somatostatin 28(1-12) by using the avidin-biotin complex immunocytochemical technique followed by in situ hybridization using 35S-labelled antisense riboprobes to somatostatin mRNA. The results of such analysis revealed that somatostatin 28 and somatostatin mRNA are 100% colocalized. Somatostatin 14 and somatostatin 28(1-12), in contrast, are only present within 66% of the neurons that express somatostatin mRNA. Examination of the anatomical distribution of neurons that express both somatostatin mRNA and somatostatin 14 or somatostatin 28(1-12) protein reveals that these neurons are present throughout the caudate-putamen of rat but are more prevalent in the ventromedial regions. Neurons that express somatostatin mRNA but not somatostatin 14 or somatostatin 28(1-12) are also present throughout the caudate-putamen but are most numerous within a dorsolateral strip just beneath the corpus callosum. These results suggest that the somatostatin neuron population within the rat caudate-putamen is actually composed of two smaller subpopulations based on neuropeptide content. The first subpopulation contains somatostatin 28 and constitutes one-third of the total somatostatin population, whereas the other contains somatostatin 28, somatostatin 14, and somatostatin 28(1-12) and represents the remaining two-thirds of the cells that express somatostatin mRNA.

D2 dopamine receptor mRNA distribution in cholinergic and somatostatinergic cells of the rat caudate-putamen and nucleus accumbens

An in situ hybridization procedure that identifies cells expressing D2 dopamine receptor mRNA was combined in double-labelling studies with immunohistochemical procedures that identify cells expressing either choline acetyltransferase (ChAT) or somatostatin. D2 receptor mRNA was detected in almost all of the ChAT positive caudate-putamen cells, approximately half of the ChAT positive nucleus accumbens cells and none of the somatostatin-positive cells in either brain region.

Acute administration of alcohol blocks cocaine-induced striatal c-fos immunoreactivity protein in the rat

Immediate-early genes, such as c-fos, are induced in the brain by cocaine and other psychotropic drugs. This induction is thought to be mediated via the activation of dopamine D1 and glutamate N-methyl-D-aspartate (NMDA) receptor subtypes. Because alcohol selectively blocks NMDA receptor function, we determined the ability of alcohol to block the expression of c-fos normally induced by systemic cocaine exposure in perikarya of the rat striatum. Acute administration of alcohol (2 g/kg; IP) approximately 30 min prior to a single cocaine (20 mg/kg) injection significantly reduced the patchy appearance of intensely immunoreactive gene signal in dorsal-central quadrants of the caudate putamen. Separate administration of three doses of alcohol alone (1, 2, or 3 g/kg) was ineffectual in inducing FOS-like protein in this or other regions of the rat brain. The blockade of the encoded protein by alcohol was partial in magnitude reminiscent of that produced by MK-801 and related NMDA receptor antagonist drugs. Furthermore, the blockade of cocaine-induced FOS-like protein by alcohol occurred at a dose which produced a blood alcohol concentration of approximately 180 mg/dl (40 mM), comparable to that detected in intoxicating humans. Considering the fact that the concomitant use of alcohol and cocaine is the most common substance abuse pattern found in the addictive population, the present results suggest an antagonist effect exerted by these two drugs at the transcriptional level and further support the consensus that NMDA receptors are the plausible surface-target elements mediating some of the effects of alcohol and cocaine.

Intracellular response of neurons of the caudate nucleus and putamen to intrastriatal stimulation in cat

The purpose of this research was to determine if the different functional areas of the striatum, as defined by corticostriate connections, have excitatory and/or inhibitory interconnections. In cats anesthetized with barbiturates, an intracellular recording electrode was angled at 45 degrees such that it (1) crossed all functional areas of the striatum in a single pass and (2) traversed perpendicular to intrastriatal axonal bundles and their terminal fields. > 95% of the neurons recorded intracellularly in the head of the caudate (Cd) nucleus responded to stimulation of the rostromedial striatum (limbic area) producing an initial excitatory response in all cases. Membrane hyperpolarization and inhibition followed the initial excitatory response in approximately half of the responsive neurons. As the recording electrode approached the stimulating electrode, latencies to response onset decreased and amplitudes of the initial excitatory responses increased. Stimulation of a single site produced responses in neurons found in all functional areas of the Cd nucleus. Based on the known topography of afferents to the striatum, these results cannot be explained by stimulation of fibers en passant. Therefore, we conclude that the limbic striatum is connected to other functional areas of the Cd nucleus by intrinsic excitatory and inhibitory circuits. We speculate that intrinsic circuits are a hidden layer of organization providing connectional plasticity by which the influence of an input on striatal neurons may be expanded or contracted beyond the anatomical limits of the afferent terminal field.

The role of putamen and pallidum in motor initiation in the cat. I. Timing of movement-related single-unit activity

The participation of basal ganglia in motor initiation was studied in six cats operantly trained to perform a ballistic flexion movement, triggered after a brief sound in a simple reaction time condition or delayed after the same sound in the presence of a tone cue. The activity of 356 neurons was recorded in the putamen and in the pallidum (globus pallidus and entopeduncular nucleus). A total of 19.4% of the neurons were not related to the conditioned flexion movement: they were either unrelated to the task (10.1%) or related to other periods of the motor performance such as trial beginning or reward delivery (9.3%). About 60% of the remaining neurons--defined as task-related--exhibited changes in firing rate that occurred, in the reaction time condition, less than 100 ms after the go signal and therefore began prior to movement onset. For most neurons, in the delayed condition, these early changes were absent, suggesting that their occurrence in the reaction time condition was not a sensory response but rather was related to the movement initiation. In addition, for many neurons these changes shifted in time, remaining time-locked to the movement. Correlations between these early changes in activity and motor parameters were demonstrated, suggesting that these changes were movement-related. For most neurons the firing levels observed during intertrial intervals and during foreperiod were similar. The mean discharge rate during the foreperiod was 19.2 impulses/s. Three patterns of activity were observed before movement: increases in discharge rate (61% of task-related neurons), transient decreases followed by increases (11%), or prolonged decreases (28%). Only minor differences were found between the characteristics of the populations of neurons recorded in the three sites under study: on average the neurons recorded in the globus pallidus were more active than the neurons recorded in the putamen or in the entopeduncular nucleus. The fact that, for certain neurons, the changes of activity prior to movement were different in reaction time condition and in delayed condition showed that the pattern of activity preceding movement might depend on the temporal requirements for motor initiation. Taken together with the motor effects obtained in the same task following GABA-receptor activation with muscimol microinjections in these structures, the present results suggest that putamen and pallidal neurons participate in the initiation of the conditioned movement under study.

A simple method to improve the reliability of iontophoretic administration of tracer substances

Microiontophoresis is a widely used technique for depositing tracer materials into the central nervous system for neuroanatomical experiments. However, the reliability of iontophoretic injection is often less than optimal. Coating the lumen of glass micropipettes with silicone to reduce surface tension reduced the incidence of failure for iontophoretic deposition of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) from 40% to zero. Similar results were observed with other tracer substances. Siliconizing the internal surface of glass micropipettes can significantly improve the reliability of iontophoretic deposition.

Morphological assessment of grafted rat and mouse cortical neurons: a light and electron microscopic study

The morphology of cortical neurons grafted into (or near) the rat striatum was studied by means of intracellular Lucifer yellow injections in fixed slices. Rat donor syngeneic cortical tissue (from postnatal day 1 old rats; AO strain) as well as mouse donor xenogeneic cortical tissue (prenatal day 19; C3H/HE strain) were grafted as solid pieces into 8-12 week-old rats (AO strain). Recipients of mouse xenografts were immunosuppressed with a monoclonal antibody against the interleukin-2 receptor. After perfusion and sectioning of the graft-containing areas, individual slices were incubated in the DNA stain 4.6-diamidino-2-phenylindole (DAPI) to visualize the cell nuclei. Grafts could be easily identified by a surrounding rim of astrocytes which outline the border between grafted and host tissue. Grafted cortical neurons were intracellularly filled with Lucifer yellow, DAB-photoconverted, and further processed for light and electron microscopy. In general, no cortical lamination could be observed in the grafted rat and mouse cortical tissue, but neurons were loosely packed throughout the graft. Two major cell types could be identified in all grafts investigated so far. The majority resembled those described as spiny neurons (85%), which could be further classified into pyramid-like, spiny stellate-like or fusiform spiny neurons, with somata ranging between 15 and 25 microns in diameter. The remaining 15% resembled non-spiny neurons with either a multipolar basket-like or fusiform morphology. Dendrites of spiny and non-spiny neurons, which could extend to distances up to 400 microns, were never seen to cross the astrocytic border, but some main axon and axonal collaterals of spiny neurons were found to leave the graft. On the basis of light microscopic observations no difference was found between mouse and rat grafted cortical neurons. The results of this study show that grafted cortical neurons retain some of the characteristic features of neurons in the intact adult cerebral cortex, although there appears to be a greater preponderance of spiny neurons in grafted tissue. This may reflect an immaturity of the grafted tissue or a response to the striatal environment.

Re-expression of glia-derived nexin/protease nexin 1 depends on mode of lesion-induction or terminal degeneration: observations after excitotoxin or 6-hydroxydopamine lesions of rat substantia nigra

The serine protease inhibitor and neurite outgrowth promoter glia derived nexin (GDN) is expressed in the rat CNS during embryogenesis and persists in the olfactory system of the adult where receptor neurons are replaced throughout life. We investigated whether GDN-immunoreactivity also appears in the adult at sites of synaptic rearrangement following nerve cell death and anterograde terminal degeneration in experimental models for Parkinson's disease. Rat substantia nigra was unilaterally lesioned by stereotaxic application of different toxins: 6-hydroxydopamine, which selectively destroys dopaminergic neurons, the excitotoxic glutamate analog ibotenic acid, or the glutamate receptor agonists N-methyl-D-aspartate and quisqualate, which cause circumscript lesions of the whole substantia nigra. Nerve cell death and astroglial reactivity were monitored by parallel cresyl staining and immunocytochemistry for glial fibrillary acidic protein, at survival times ranging from 2 to 100 days. Sustained de novo synthesis of GDN occurred in the dopamine depleted caudate putamen following excitotoxin or 6-hydroxydopamine induced degeneration of the substantia nigra and of the nigrostriatal pathway provided that the lesions were nearly complete. This is consistent with compensatory changes occurring in deafferented caudate putamen and suggests a permissive role of GDN in neuronal plasticity. In the substantia nigra astroglia exhibited GDN-immunoreactivity following excitotoxin injection but not after application of 6-hydroxydopamine. Thus differences in action mechanisms of neurotoxins may have distinct consequences on the astrocyte mediated response of the same affected brain region.

A bimodal map of space: somatosensory receptive fields in the macaque putamen with corresponding visual receptive fields

The macaque putamen contains neurons that respond to somatosensory stimuli such as light touch, joint movement, or deep muscle pressure. Their receptive fields are arranged to form a map of the body. In the face and arm region of this somatotopic map we found neurons that responded to visual stimuli. Some neurons were bimodal, responding to both visual and somatosensory stimuli, while others were purely visual, or purely somatosensory. The bimodal neurons usually responded to light cutaneous stimulation, rather than to joint movement or deep muscle pressure. They responded to visual stimuli near their tactile receptive field and were not selective for the shape or the color of the stimuli. For cells with tactile receptive fields on the face, the visual receptive field subtended a solid angle extending from the tactile receptive field to about 10 cm. For cells with tactile receptive fields on the arm, the visual receptive field often extended further from the animal. These bimodal properties provide a map of the visual space that immediately surrounds the monkey. The map is organized somatotopically, that is, by body part, rather than retinotopically as in most visual areas. It could function to guide movements in the animal's immediate vicinity. Cortical areas 6, 7b, and VIP contain bimodal cells with very similar properties to those in the putamen. We suggest that the bimodal cells in area 6, 7b, VIP, and the putamen form part of an interconnected system that represents extra personal space in a somatotopic fashion.

Output architecture of the primate putamen

The basal ganglia act through direct and indirect striatopallidal output pathways that have different effects on cortical activity. This division has been proposed to underlie the fundamental distinction between hyperkinetic and hypokinetic movement disorders such as Parkinson's disease and Huntington's disease. Evidence to date does not favor a relationship between this dual organization and the division of the striatum into striosome and matrix compartments. However, the possibility has been raised that the division of striatopallidal output paths reflects a compartmentalization of the matrix itself into clusters of different striatopallidal projection neurons. We directly tested this hypothesis in squirrel monkeys by comparing the distributions of striatal output neurons retrogradely labeled from the two pallidal segments. Striatopallidal neurons labeled by small injections confined to either the external pallidum (GPe) or the internal pallidum (GPi) formed small clusters ("matrisomes") in the matrix compartment of the putamen. However, contrary to previous predictions, labeled matrisomes projecting to GPe were not systematically separated from those projecting to GPi. They could overlap extensively, and within individual matrisomes GPe-projecting neurons and GPi-projecting neurons were extensively intermixed. Double-retrograde labeling analysis in single sections demonstrated that only 2.1 +/- 2.7% of labeled striatal neurons were doubly labeled from both GPe and GPi--a number not significantly different from zero. GPe-projecting and GPi-projecting neurons in the putamen also differed sharply in their expression of enkephalin-like immunoreactivity: 71.3 +/- 7.6% of the neurons labeled by GPe injections were enkephalin positive, in contrast to 10.0 +/- 3.6% of the neurons labeled by GPi injections. These results suggest that in the primate, populations of striatopallidal output neurons are grouped in clusters in the matrix, but that individual neurons in any given cluster project either to GPe or to GPi. Matrisomal clustering may thus coordinate signals sent into the direct and indirect pathways of the basal ganglia from distributed populations of projection neurons in the striatum.

Dopamine and acetylcholine cell density in the neuroleptic responsive (NR) and neuroleptic nonresponsive (NNR) lines of mice

The neuroleptic responsive (NR) and neuroleptic nonresponsive (NNR) selected lines of mice differ more than 10-fold in the ED50 for catalepsy induced by a wide variety of neuroleptics with a high dopamine D2/D1 receptor activity ratio, e.g., haloperidol. The NR and NNR lines also differ significantly in dopamine D2 somatodendritic receptor density; within the substantia nigra zona compacta and the ventral tegmental area, the increases in the NNR line are on average 33 and 48%, respectively. We now report that the NNR line has a higher number of dopamine neurons in the midrostral to the midcaudal aspect of the substantia nigra zona compacta. Within this region, the increase in dopamine cell number was on average 41%. In contrast to these data, there was no difference in cell number between lines in the ventral tegmental area. Thus, the increase of midbrain dopamine D2 receptor density in the NNR line can only be accounted for in part by an increase in the number of dopamine neurons. Although the number of dopamine neurons in the substantia nigra zona compacta was increased in the NNR line, the density of dopamine terminals in the caudate-putamen as estimated by the [3H] mazindol technique was modestly but significantly higher (8%) in the NR line. The selected lines also differed within the caudate-putamen in the number of cholinergic neurons. The NR line had a significantly higher number of cholinergic neurons in the rostral caudate-putamen. Overall, these data illustrate that selective breeding for neuroleptic response has yielded lines of mice with significant differences in both the cholinergic and dopaminergic systems of the basal ganglia.

Extracellular gamma-aminobutyric acid levels in the rat caudate-putamen: monitoring the neuronal and glial contribution by intracerebral microdialysis

Intracerebral microdialysis with high pressure liquid chromatography (HPLC) coupled to electrochemical detection was employed to characterize gamma-aminobutyric acid (GABA) release and the effects induced by a preceding neuron-depleting ibotenic acid (IBO) lesion in the rat caudate-putamen (CPu). Extracellular GABA overflow was monitored in the intact and excitotoxically lesioned CPu, either 7-10 days (acute) or more than 3 months post-lesioning (chronic), using loop type dialysis probes perfused at a rate of 2 microliters/min. In the intact CPuu, basal GABA levels were 0.97 pmol/30 microliters of dialysate in the awake animals and 0.76 pmol/30 microliters under halothane anaesthesia. In both the acute and chronic IBO lesioned CPu the extracellular GABA levels were reduced by 80% and 67%, respectively, under halothane anaesthesia. KCl added to the perfusion fluid at a concentration of 100 mM resulted in dramatic increases in GABA overflow from baseline levels in the intact CPu (60- to 70-fold), which were almost totally abolished (> 95%) in the excitotoxically lesioned CPu. Veratridine administered at 75 microM, produced a 45-fold increase in GABA overflow in the intact CPu, but failed to produce any effect in the lesioned CPu. The addition of nipecotic acid (0.5 mM), a GABA uptake blocker, increased basal extracellular GABA levels 6-15-fold in the intact CPu, while GABA overflow in either the acute or chronic lesioned CPu was not significantly altered. Although Ca(2+)-free conditions (with 20 mM Mg2+ added) or tetrodotoxin (TTX, 1 microM) did not alter the basal GABA overflow in the intact CPU under halothane anaesthesia, the omission of Ca2+ resulted in a 47% reduction in basal extracellular GABA levels in awake, freely moving animals. Nipecotic acid-induced GABA overflow was reduced by 22% under Ca(2+)-free conditions, and by 33% in the presence of 1 microM TTX. Moreover, KCl-evoked GABA overflow was reduced by 86% in Ca(2+)-free conditions and by 40% when administered in the presence of 1 microM TTX. These results indicate that the extracellular GABA levels recorded by intracerebral microdialysis in the CPu are derived predominantly from neuronal sources. Under baseline resting conditions only a small fraction (up to 20-30%) of the neuronal release was Ca(2+)-dependent and TTX-sensitive (i.e. possessing the characteristics of impulse-dependent vesicular release).(ABSTRACT TRUNCATED AT 400 WORDS)

Striatal connections of the parietal association cortices in rhesus monkeys

The corticostriatal connections of the parietal association cortices were examined by the autoradiographic technique in rhesus monkeys. The results show that the rostral portion of the superior parietal lobule projects predominantly to the dorsal portion of the putamen, whereas the caudal portion of the superior parietal lobule and the cortex of the upper bank of the intraparietal sulcus have connections with the caudate nucleus as well as with the dorsal portion of the putamen. The medial parietal convexity cortex projects strongly to the caudate nucleus, and has less extensive projections to the putamen. In contrast, the medial parietal cortex within the caudal portion of the cingulate sulcus projects predominantly to the dorsal portion of the putamen, and has only minor connections with the caudate nucleus. The rostral portion of the inferior parietal lobule projects mainly to the ventral sector of the putamen, and has only minor connections with the caudate nucleus. The middle portion of the inferior parietal lobule has sizable projections to both the putamen and the caudate nucleus. The caudal portion of the inferior parietal lobule as well as the lower bank of the intraparietal sulcus project predominantly to the caudate nucleus, and have relatively minor connections with the putamen. The cortex of the parietal opercular region also shows a specific pattern of corticostriatal projections. Whereas the rostral portion projects exclusively to the ventral sector of the putamen, the caudal portion has connections to the caudate nucleus as well. Thus, it seems that parietostriatal projections show a differential topographic distribution; within both the superior and the inferior parietal region, as one progresses from rostral to caudal, there is a corresponding shift in the predominance of projections from the putamen to the caudate nucleus. In addition, with regard to the projections to the putamen, the superior parietal lobule is related mainly to the dorsal portion, and the inferior parietal lobule to the ventral portion. The striatal projections of the cortex of the caudal portion of the cingulate gyrus (corresponding in part to the supplementary sensory area) and of the rostral parietal opercular region (corresponding in part to the second somatosensory area) are directed almost exclusively to the dorsal and ventral sectors of the putamen, respectively. This pattern resembles that of the primary somatosensory cortex. The results are discussed with regard to the overall architectonic organization of the posterior parietal region. Possible functional aspects of parietostriatal connectivity are considered in the light of physiological and behavioral studies.

The histochemical demonstration of MPTP oxidation in the postmortem human striatum

Monoamine oxidase (MAO) histochemistry has been performed in postmortem human striatal tissues using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as substrate. The reaction products of MPTP oxidation in the human putamen and caudate nucleus were observed in glial cells. Although glial staining was found diffusely in the human striatum, prominently intense staining was observed in glial cells surrounding vessels. Double staining for MAO and glial fibrillary acidic protein showed that glial cells containing MAO activity were astrocytes. The inhibition experiments using clorgyline and 1-deprenyl as MAO inhibitors indicate that MAO associated with the present MPTP oxidation was of the B type. The present observations suggest that astrocytes, especially around vessels, may be involved in MPTP oxidation in the human striatum after systemic administration of MPTP.