Changes in cortical and subcortical levels of monoamines and their metabolites following unilateral ventrolateral cortical lesions in the rat

Serotonin 5-HT1A receptors modulate depression-related symptoms following mild traumatic brain injury in male adult mice

Traumatic brain injury is a complex phenomenon leading to neurological diseases and persistent disability that currently affects millions of people worldwide. Increasing evidence shows that a wide range of patients with mild traumatic brain injury (mTBI) suffer from depression during the initial stages of injury and the post-acute stages of recovery. However, the underlying mechanisms involved in depression following mTBI are still not fully understood. The aim of this study was to determine whether serotonin 5-hydroxytryptamine-1A (5-HT1A) receptor is involved in the regulation of depression-related behaviors following mild traumatic brain injury in mice. Mice with or without mTBI received intracerebroventricular injections of 5-HT1A receptor agonist (8-OH-DPAT) or antagonist (WAY-100635) for 5 days, then animals were subjected to behavioral tests. Four behavioral tests including novelty-suppressed feeding test, forced swim test, sucrose preference test and tail suspension test were used to evaluate depression-related symptoms in animals. Our results indicated that mTBI induction increased depression-like symptoms through altering serotonin 5-HT1A receptor activity in the brain. Activation of 5-HT1A receptor by a subthreshold dose of 8-OH-DPAT led to a significant decrease in depression-like behaviors, whereas blockade of 5-HT1A receptor by a subthreshold dose of WAY-100635 resulted in a considerable increase in depression-like phenotypes in mTBI-induced mice. The major strength of the present study is that depression-related symptoms were assessed in four behavioral tests. The present study supports the idea that disturbances in the function of serotonergic system in the brain following mTBI can play an important role in the regulation of depression-related behaviors.

Neurotransmitter Systems in a Mild Blast Traumatic Brain Injury Model: Catecholamines and Serotonin

Exposure to improvised explosive devices can result in a unique form of traumatic brain injury--blast-induced traumatic brain injury (bTBI). At the mild end of the spectrum (mild bTBI [mbTBI]), there are cognitive and mood disturbances. Similar symptoms have been observed in post-traumatic stress disorder caused by exposure to extreme psychological stress without physical injury. A role of the monoaminergic system in mood regulation and stress is well established but its involvement in mbTBI is not well understood. To address this gap, we used a rodent model of mbTBI and detected a decrease in immobility behavior in the forced swim test at 1 d post-exposure, coupled with an increase in climbing behavior, but not after 14 d or later, possibly indicating a transient increase in anxiety-like behavior. Using in situ hybridization, we found elevated messenger ribonucleic acid levels of both tyrosine hydroxylase and tryptophan hydroxylase 2 in the locus coeruleus and the dorsal raphe nucleus, respectively, as early as 2 h post-exposure. High-performance liquid chromatography analysis 1 d post-exposure primarily showed elevated noradrenaline levels in several forebrain regions. Taken together, we report that exposure to mild blast results in transient changes in both anxiety-like behavior and brain region-specific molecular changes, implicating the monoaminergic system in the pathobiology of mbTBI.

In vivo imaging of microglial activation using a peripheral benzodiazepine receptor ligand: [11C]PK-11195 and animal PET following ethanol injury in rat striatum

OBJECTIVE

To investigate whether [(11)C]PK-11195, a specific peripheral benzodiazepine receptors (PBRs) ligand for positron emission tomography (PET), can show activated microglia in a rat brain injury model.

METHODS

On day 1, ethanol was injected into the rat's right striatum (ST) using a stereotaxic operative procedure. On day 3, head magnetic resonance imaging (MRI) scans for surgically treated rats were performed to evaluate ethanol injury morphologically. On day 4, dynamic PET scans (17 injured rats and 7 non-injured controls) were performed for 60 min with an animal PET scanner under chloral hydrate anesthesia following a bolus injection of [(11)C]PK-11195 through tail vein. Because PBRs are present throughout the brain, there is no suitable receptor-free reference region. The reference tissue model may not be applicable because of low target to background ratio for low affinity of [(11)C]PK-11195 to PBRs. We evaluated the PBRs binding with regions of interest (ROIs)-based approach to estimate total distribution volume (V). We used an integral from 0 min to 60 min (V (60)) as an estimate of V. On the coronal PET image, ROIs were placed on bilateral ST. Differences in right/left ST V (60) ratios between lesioned and unlesioned control rats were compared using unpaired t tests. Immunohistochemical staining was performed for confirming the presence of activated microglia following decapitation on the PET experiment day.

RESULTS

The right/left ST V (60) ratios in lesioned rats (1.07 +/- 0.08) were significantly higher than those in unlesioned control rats (1.00 +/- 0.06, P < 0.05). On immunohistochemical staining, activated microglia were exclusively observed in the injured right ST but not in the noninjured left ST of the injury rats and the bilateral ST of the non-injured control rats.

CONCLUSIONS

These results suggest that [(11)C]PK-11195 PET imaging would be a useful tool for evaluating microglial activation in a rat brain injury model.

Prevalence of bipolar symptoms in epilepsy vs other chronic health disorders

OBJECTIVE

To estimate the comparative prevalence of bipolar symptoms in respondents with epilepsy vs other chronic medical conditions.

METHODS

The Mood Disorder Questionnaire (MDQ), a validated screening instrument for bipolar I and II symptoms, in conjunction with questions about current health problems, was sent to a sample of 127,800 people selected to represent the US adult population on selected demographic variables. A total of 85,358 subjects (66.8%) aged 18 or older returned the survey and had usable data. Subjects who identified themselves as having epilepsy were compared to those with migraine, asthma, diabetes mellitus, or a healthy comparison group with regard to relative lifetime prevalence rates of bipolar symptoms and past clinical diagnoses of an affective disorder.

RESULTS

Bipolar symptoms, evident in 12.2% of epilepsy patients, were 1.6 to 2.2 times more common in subjects with epilepsy than with migraine, asthma, or diabetes mellitus, and 6.6 times more likely to occur than in the healthy comparison group. A total of 49.7% of patients with epilepsy who screened positive for bipolar symptoms were diagnosed with bipolar disorder by a physician, nearly twice the rate seen in other disorders. However, 26.3% of MDQ positive epilepsy subjects carried a diagnosis of unipolar depression, and 25.8% had neither a uni- nor bipolar depression diagnosis.

CONCLUSION

Bipolar symptoms occurred in 12% of community-based epilepsy patients, and at a rate higher than in other medical disorders. One quarter were unrecognized.

Localization of ionotropic glutamate receptors in caudate-putamen and nucleus accumbens septi of rat brain: comparison of NMDA, AMPA, and kainate receptors

Changes in binding of selective radioligands at NMDA ([3H]MK-801), AMPA ([3H]CNQX), and kainate ([3H]kainic acid) glutamate (GLU) ionotropic receptors in rat caudate-putamen (CPu) and nucleus accumbens (NAc) were examined by quantitative autoradiography following: 1) unilateral surgical ablation of frontal cerebral cortex to remove descending corticostriatal GLU projections, 2) unilateral injection of kainic acid (KA) into CPu or NAc to degenerate local intrinsic neurons, or 3) unilateral injections of 6-hydroxydopamine (6-OH-DA) into substantia nigra to degenerate ascending nigrostriatal dopamine (DA) projections. Cortical ablation significantly decreased NMDA receptor binding in ipsilateral medial CPu (20%), and NAc (16%), similar to previously reported losses of DA D4 receptors. KA lesions produced large losses of NMDA receptor labeling in CPu and NAc (both by 52%), AMPA (41% and 45%, respectively), and kainate receptors (40% and 45%, respectively) that were similar to the loss of D2 receptors in CPu and NAc after KA injections. Nigral 6-OH-DA lesions yielded smaller but significant losses in NMDA (17%), AMPA (12%), and kainate (11%) receptor binding in CPu. The results indicate that most NMDA, AMPA, and kainate receptors in rat CPu and NAc occur on intrinsic postsynaptic neurons. Also, some NMDA, but not AMPA or kainate, receptors are also found on corticostriatal projections in association with D4 receptors; these may, respectively, represent excitatory presynaptic NMDA autoreceptors and inhibitory D4 heteroceptors that regulate GLU release from corticostriatal axons in medial CPu and NAc. Conversely, the loss of all three GLU receptor subtypes after lesioning DA neurons supports their role as excitatory heteroceptors promoting DA release from nigrostriatal neurons.

Diminished serotonin-mediated prolactin responses in nondepressed stroke patients compared with healthy normal subjects

BACKGROUND AND PURPOSE

The purpose of this study was to use hormonal responsiveness to d-fenfluramine (d-FEN) challenge as a measure of central serotonin (5-HT) function in a comparative evaluation of serotonergic abnormalities between stroke patients and healthy elderly normal subjects to test the hypothesis that stroke may be associated with diminished serotonergic functioning.

METHODS

Eight nondepressed medically stable stroke patients and 12 healthy volunteers completed a single-blind, placebo-controlled, fixed-order, crossover design challenge test with 30 mg of oral d-FEN. Baseline prolactin (PRL) and cortisol (CORT) and hormonal responses to d-FEN and placebo were measured at hourly intervals over a 4-hour period. Cardiovascular responses (pulse and blood pressure) and behavioral responses were also recorded at the same time points.

RESULTS

The 2 groups were comparable in demographics, body weight, plasma drug concentration, and behavioral and CORT responses. A 3-way ANOVA for repeated measures showed group differences for baseline adjusted PRL responses (change of scores from baseline). Peak PRL responses (maximal PRL change from baseline scores after treatment with d-FEN) in nondepressed stroke patients were attenuated compared with healthy elderly subjects, suggesting diminished serotonergic responsiveness in stroke patients.

CONCLUSIONS

The demonstrated serotonergic hypofunctioning poststroke may contribute to the high incidence of depressive disorders in stroke patients. Serotonergic agents may have a role in augmentation of stroke recovery.

Microglial NO induces delayed neuronal death following acute injury in the striatum

We have established a novel injury model in the central nervous system by a stereotaxic injection of ethanol into rat striatum to induce necrosis. With this model, we clarify a function of inducible nitric oxide synthase (iNOS) in a healing mechanism around a necrotic lesion. A semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) revealed that the iNOS mRNA arose at 6 h, peaked at 24 h, and declined to a lower level 48 h after an intrastriatal 5-microL ethanol injection. From in situ hybridization, this iNOS mRNA was expressed in the area surrounding the injury. By immunohistochemistry, mononuclear cells at this boundary area of necrosis were stained with anti-iNOS antibody on the first day after the injury. These cells turned out to be reactive microglia from the positive staining of GSA-I-B4, ED-1 and OX-42. Haematoxylin-eosin (HE) staining showed that neurons in this boundary area gradually disappear up to 5 days after the injury with an increment of microglial cells, and this area became cavernous. Nuclei of neurons in this area were stained positive by the terminal deoxynucleotidyl-transferase-mediated dUTP-biotin nick end-labelling (TUNEL) assay on the first day after the injury. These TUNEL-positive neurons gradually disappeared toward the third day, while microglial cells increased. L-Ng-nitro-arginine methylester (L-NAME), a competitive NOS inhibitor, administration diminished the elimination of neurons by microglia in this boundary area surrounding necrosis. Microglial NO may act as a neurotoxic agent to eliminate damaged neurons near the necrosis in the form of delayed neuronal death, and may reintegrate the neuronal circuits with functionally intact neurons.

Localization of dopamine receptor subtypes in corpus striatum and nucleus accumbens septi of rat brain: comparison of D1-, D2- and D4-like receptors

Changes in D1-, D2- and D4-like dopamine receptor binding in rat brain were examined by quantitative autoradiography following: (i) unilateral surgical ablation of frontal cerebral cortex to remove descending projections to corpus striatum and nucleus accumbens, (ii) unilateral injections of kainic acid into corpus striatum or nucleus accumbens to degenerate local intrinsic neurons, (iii) unilateral injections of 6-hydroxydopamine into substantia nigra to degenerate ascending dopamine projections. Rats were killed one week after lesioning, with contralateral tissue controls. Radioligands were: [3H]SCH-23390 for D1-like (D1/D5) receptors, [3H]nemonapride alone for D2-like (D2/D3/D4) receptors, and [3H]nemonapride with 300 nM S[-]-raclopride and other masking agents for D4-like receptors (identified by blockade with D4 selective L-745,870). Frontal cerebral cortex ablation did not alter D1- or D2-like receptor density, but D4-like binding decreased significantly in both corpus striatum (18%) and nucleus accumbens (23%). Kainic acid markedly reduced D1-like (75% and 84%) and D2-like binding (44% and 52%), with smaller D4-like losses (28% and 27%) in corpus striatum and nucleus accumbens, respectively. Nigral 6-hydroxydopamine lesions (verified by autoradiographic loss of dopamine transporters labelled with [3H]GBR-12935) did not significantly change D1-, D2-, or D4-like binding in the corpus striatum. These results suggest that the majority of D1-, and D2-like, and a smaller portion of D4-like receptors in corpus striatum and nucleus accumbens arise on intrinsic postsynaptic neurons, and that some D4-like, but neither D1- nor D2-like, receptors are found on presynaptic corticostriatal afferents.

Neuropsychiatric sequelae of stroke and traumatic brain injury: the role of psychostimulants

OBJECTIVE

The primary purpose of this article is to review certain neuropsychiatric sequelae of stroke and traumatic brain injury (TBI), and the role of the psychostimulants methylphenidate (MPD) and dextroamphetamine (DAMP) in their treatment.

METHOD

A general review of the topic is presented. Controlled and uncontrolled studies involving the use of the psychostimulants are discussed. These consist of 11 studies listed with Medline 2000 that deal specifically with stroke or head injury, with the oldest study reviewed dating back to 1984. Studies concerning the use of psychostimulants in the medically or neurologically ill are reviewed to the extent that they are pertinent.

RESULTS

The current literature consists primarily of uncontrolled case studies. However, these are reviewed and found to suggest a role for the use of the psychostimulants, which is discussed.

CONCLUSIONS

In general, these drugs appear to be a reasonable treatment choice for certain types of mood, behavior, and cognitive symptoms following brain injury. However, it is noted that larger scale controlled studies are needed to adequately assess the clinical usefulness of these drugs.

Behavioral and neurochemical indices of barrel cortex-basal ganglia interaction

Previous experiments from our laboratory have shown a wide variety of time-dependent lateralized changes in behavior and nigrostriatal function following unilateral manipulation of the mystacial vibrissae of rats. The present experiment investigated the effects of unilateral radiofrequency lesion of the cortical vibrissae representation (the barrel fields) in light of these results. We measured lateralized changes in behavior as well as tissue monoamines in neostriatum and substantia nigra, between 1 and 16 days post-lesion. Short-term asymmetries in exploratory behavior (thigmotactic scanning) and neostriatal serotonin metabolism that lasted up to day 6 were seen. In substantia nigra, time-related asymmetries in dopamine concentrations were found with higher ipsilateral values on day 3 and higher contralateral values on day 6. After day 6, the animals had recovered from these acute effects and thereafter, neostriatal dopamine metabolism became asymmetrical. Also during this time, they showed a directional bias in spontaneous and apomorphine-induced turning. Finally, neostriatal serotonin was bilaterally elevated on day 16. These results parallel some of the effects previously seen following unilateral removal of the vibrissae, indicating that the barrel cortex is a critical link in the functional interaction between the vibrissae and basal ganglia.

Olfactory bulbectomy as a model for agitated hyposerotonergic depression

Ablation of olfactory bulbs in rats reduced male sexual behavior, and altered the distribution of wheel-running activity between the light and dark phases of a 12:12 LD photoperiod. These effects were partially reversed by the tricyclic antidepressant amitriptyline. Olfactory bulbectomy also altered serotonin metabolism (5-HIAA/5-HT ratio) in the frontal cortex, nucleus accumbens, hippocampus and corpus striatum. These observations support the hypothesis that olfactory bulbectomy in rodents serves as a model of agitated hyposerotonergic depression.

Brain injury: new insights into neurotransmitter and receptor mechanisms

The studies reviewed here represent a continuing search for mechanisms which play a role in neurological disturbances resulting from brain injury. Focal cortical freezing lesions in rats were shown to cause a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity. Such an interpretation was supported by the finding that in lesioned brain reduction of cerebral metabolism by pentobarbital and isoflurane was limited by the metabolic depression that has already occurred as a result of injury and by the demonstration that the energy status and substrate (glucose) supply in the cortical areas in the injured brain have not been compromised at the time when LCGU was decreased. Both the serotonergic and the noradrenergic neurotransmitter systems were implicated in functional alterations associated with injury. Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere and complete inhibition of 5-HT synthesis with p-chlorophenylalanine ameliorated the decrease in cortical LCGU, interpreted as reflecting cortical functional depression. Cortical norepinephrine metabolism was bilaterally increased in focally injured brain, while prazosin, a selective alpha 1-noradrenergic receptor blocker, normalized cortical LCGU in the lesioned hemisphere. Low-affinity in vivo binding of [125I]HEAT, another selective alpha 1-receptor ligand, was specifically increased in cortical areas of the lesioned hemisphere at the time of the greatest depression in LCGU, suggesting that alpha 1-adrenoreceptors may be of functional importance in injured brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Asymmetrical effects of cortical ablation on brain monoamines in mice

Neurochemical changes induced by right or left cortical ablation which have previously been described to have immunological effects were investigated in mice. Catecholamine and indolamine levels were determined in the contralateral cortex and in subcortical structures involved in immunoregulation 14 and 60 days after unilateral cortical ablation. Unilateral cortical ablation induced profound and widespread changes in the contralateral cortex but also in subcortical regions of both sides at 14 days after surgery. Lesions of the left neocortex appeared mainly to affect the activity of serotoninergic inputs to the right neocortex, whereas ablations of the right cortex influenced the activity of the catecholaminergic inputs to the left. Sixty days after surgery, modifications in monoamine levels were observed only in the ipsilateral, but not contralateral, subcortical regions, the only exception being that DA turnover in the tuberoinfundibular system remained lowered in both hemispheres after either right or left cortical ablations. Furthermore, some asymmetrical effects of cortical lesions depended on functional brain lateralization as assessed by paw preference. It may be hypothesized that some neurochemical modifications induced by unilateral cortical lesions are, at least partially, responsible for the immunological perturbations observed after cortical ablation.

Increased serotoninergic and noradrenergic activity in hepatic encephalopathy in rats with thioacetamide-induced acute liver failure

Functional changes of various neurotransmitter systems have been implicated in the pathogenesis of hepatic encephalopathy. In this study the role of brain monoaminergic neurotransmitter systems in hepatic encephalopathy was investigated in rats with thioacetamide-induced acute liver failure. Concentrations of serotonin, dopamine, noradrenaline and of their metabolites 5-hydroxyindoleacetic acid, dihydroxyphenylalanine (following inhibition of dihydroxyphenylalanine-decarboxylase), dihydroxyphenylacetic acid, homovanillic acid and 3-methoxy-4-hydroxyphenyl-glycol, were measured in the cerebral cortex, striatum and hippocampus by high performance liquid chromatography with electrochemical detection. In hepatic encephalopathy concentrations of 5-hydroxyindoleacetic acid were increased in all three brain areas (196%, 204% and 264% of saline-treated controls, p less than 0.01), and concentrations of serotonin were increased in the frontal cortex (121%, p less than 0.01). In the frontal cortex and hippocampus of encephalopathic rats dopamine levels were increased (157% and 289%, p less than 0.05), and levels of noradrenaline (53% and 46%, p less than 0.05) were decreased associated with increased 3-methoxy-4-hydroxyphenylglycol levels (173% and 206%, p less than 0.05). The extent of these changes correlated with the stage of hepatic encephalopathy. In hepatic encephalopathy dihydroxyphenylalanine accumulation was increased in the hippocampus and unchanged in the cerebral cortex. Dopamine, noradrenaline, dihydroxyphenylacetic acid and homovanillic acid concentrations were unchanged in the striatum. The results of this study indicate that hepatic encephalopathy in thioacetamide-induced acute liver failure in rats is associated with neurochemical changes, suggesting an increased activity of the noradrenergic and serotoninergic neurotransmitter systems.

Effects of isomers of hydroxyaporphines on dopamine metabolism in rat brain regions

The effects of isomers of di- and monohydroxyaporphines on cerebral dopamine (DA) metabolism were evaluated in representative extrapyramidal (corpus striatum) and limbic (nucleus accumbens septi) tissues of rat brain by three methods: (1) changes in the ratio of homovanillic acid (HVA) to DA, (2) accumulation of L-dihydroxyphenylalanine (DOPA) after inhibiting its decarboxylation to DA under "open-loop" conditions, as well as (3) after gamma-butyrolactone (GBL) pretreatment to provide selective effects at presynaptic DA autoreceptors. The DA-agonist R(-) isomers of the aporphines apomorphine (APO), N-n-propylnorapomorphine (NPA), and 11-hydroxy-N-n-propylnoraporphine (11-OH-NPa) showed consistent dose-dependent inhibition of DA synthesis in both brain regions with all models; the neuroleptic haloperidol had the opposite effect in the first two models only, as expected. The S(+) isomers of NPA and 11-OH-NPa have shown behavioral evidence of antidopaminergic activity, especially in the limbic system. Unlike the neuroleptic, S(+)NPA did not show DA-synthesis enhancing actions in accumbens or striatal tissue but, instead, inhibited DA synthesis like its R(-) antipode in all three test paradigms. S(+)11-OH-NPa given alone produced minor changes in the HVA/DA ratio and did not antagonize R(-)11-OH-NPa, weakly increased accumulation of DOPA in the second model, and had no effect in the third--all without regional selectivity. In the test of autoreceptor functioning, the dihydroxyaporphine S(+)NPA, but not S(+)11-OH-NPa, inhibited DA synthesis and this effect, in turn, was largely reversed by haloperidol, as were the inhibitory effects of the three R(-)aporphines tested. In this model, however, neither S(+)NPA nor S(+)11-OH-NPa antagonized the DA-synthesis inhibiting effect of R(-)APO as haloperidol did. Overall, these results are consistent with evidence that R(-)NPA and 11-OH-NPa have high affinity at D-2 receptor sites in rat brain and show behavioral effects of typical DA agonists. The non-stereoselective inhibitory effects of NPA on DA synthesis may reflect its activity as a weak DA agonist with very low intrinsic activity, but may also include a direct "catechol-effect" on tyrosine hydroxylase. In contrast, R(-)11-OH-NPa appears to be a stereoselective D-2 agonist, active at autoreceptors as well as postsynaptic receptors, that lacks the nonstereospecific effects on DA metabolism of its catechol-aporphine congener. It may be a useful probe for the further characterization of dopamine receptors and autoreceptors.

Changes in blood-brain barrier and cerebral blood flow following elevation of circulating serotonin level in anesthetized rats

Plasma serotonin (5-HT) was elevated by an intravenous infusion of this amine into urethane-anaesthetized rats and the concentration approximated that present in various neurological diseases and mental abnormalities. An infusion of 10 micrograms per kg body weight for 10 min significantly increased blood-brain barrier (BBB) permeability to Evans blue and 131I-sodium measured in whole brain. Regional BBB determinations with labelled 131I-sodium showed that the permeability to this compound was increased in the cerebral cortex, hippocampus, caudate nucleus, hypothalamus, colliculus and the cerebellum but not in the pons and the medulla oblongata. Regional blood flow was reduced in the same parts which showed BBB abnormality tested with 125I-labeled microspheres. Pretreatment with cyproheptadine, a 5-HT2 receptor antagonist, prevented the BBB increase and the regional blood flow was near normal values. Similar effects were obtained with indomethacin, a prostaglandin synthesis inhibitor. Vinblastine, known to influence vesicular transport, eliminated extravasation of the tracers but the regional blood flow remained depressed. A hypothesis is put forward that serotonin after binding to its receptor in the cerebral vessels stimulates prostaglandin which either directly or by means of cyclic adenosine monophosphate causes an increased vesicular transport across the endothelial cells and thus an extravasation of tracer substances in the brain. Obviously, this form of exudation can be influenced by pharmacological means.

Remote lateralized changes in cortical [3H]spiperone binding following focal frontal cortex lesions in the rat

Positron emission tomography (PET) studies in stroke patients have shown that right hemisphere lesions lead to increases in ipsilateral (compared to contralateral) cortical S2-serotonin receptors, while left hemisphere lesions do not. To assess whether similar lateralized changes in cortical S2-receptors could be demonstrated in response to brain injury in the rat, [3H]spiperone (SP) autoradiography was performed 30 days after unilateral cortical suction lesions. Right lesions produced bilateral increases in total SP binding in frontal cortex (excluding the lesion site): 48% greater than after left lesions, and 23% greater than shams. Left lesions led to bilateral decreases in S2-receptors in the frontal and perirhinal cortex and these decreases were asymmetric. There was a greater decrease in the hemisphere contralateral to the lesion than in the side with the lesion. Frontal S2-receptor binding was positively correlated with running wheel activity in all animals with lesions, regardless of lesion side. These results suggest that there is a lateralized receptor and behavioral response to focal injury in rats, analogous to that previously observed in humans.

Postnatal development of dopamine D1 and D2 receptor sites in rat striatum

Tissue was obtained from corpus striatum of maturing rats at representative postnatal ages of 8-120 days for evaluation of D1 and D2 dopamine (DA) receptor sites in radioreceptor assays based on use of 0.05-2.5 nM concentrations of [3H]SCH-23390 or [3H]domperidone, respectively. Pharmacologic selectivity was verified by high rank-correlations (rs greater than 0.90) of Ki values for representative test agents in both assays (vs 0.3 nM ligand), using striatal tissue obtained at ages 20 and 120 days. Data from repeated (3-5x) six-concentration isotherm experiments involving a wide range of D1 or D2 radioligand concentrations were analyzed by linear regression of specific binding (B) vs free ligand concentration (F) in linearized form (B/F vs B) for each replicate assay and for pooled values, as well as by curve-fitting all available raw data (B vs F) using the LIGAND program adapted to microcomputer. Values for apparent ligand affinity (Kd = 0.15-0.35 nM) failed to show a consistent change with age, while values for apparent receptor site density (Bmax) followed a similar developmental course with both methods of analysis (between methods: r = 0.99 and 0.89 for D1 and D2 assays, respectively, across all ages tested).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacology of binding of 3H-SCH-23390 to D-1 dopaminergic receptor sites in rat striatal tissue

3H-SCH-23390, a selective antagonist of D-1 dopamine (DA) receptors, was used in a radioreceptor assay with rat brain striatal tissue, optimized biochemically, and extensively characterized pharmacologically with striatal membranes. Nonspecific binding, defined with excess cis(Z)-flupenthixol (300 nM), averaged 20-25% of total counts bound. Specific binding was linearly dependent on the amount of original striatal tissue (0-4 mg) or protein (0-250 micrograms), temperature dependent, saturable and reversible, and appeared to involve a single site at ligand concentrations limited to less than 10 nM. Binding in rat brain regions ranked as: striatum greater than accumbens greater than prefrontal cortex greater than posterior cerebral cortex greater than cerebellum. Association was virtually complete within 30 min at 30 degrees, and the rate of dissociation at 30 degrees was 0.0377 min-1 (half-time = 18.4 min). Affinity (Ka or Kd) determined from association and dissociation rate constants and from concentration isotherms averaged 0.349 and 0.340 nM respectively. Including Na+ at 150 mM increased apparent maximum specific binding (Bmax) by 19%, with a 29% increase in affinity; other monovalent cations alone had small effects on specific binding; Ca2+ and Mg2+ reduced binding by 42%. Agents (N = 85) were tested for potency (Ki or IC50) in competition with the ligand (at 0.30 nM). Those known to have selective effects at D-1 receptors, generally, were most potent and stereoselective. Na+ (150 mM) had little effect on the affinity of cis-thioxanthenes but decreased that of most other agents tested with high D-1 affinity. For antipsychotic agents, the correlation of typical clinical daily doses versus Ki at D-1 sites (r = 0.06) was much lower than at D-2 sites (r = 0.94). (-)Thioridazine was discovered to be D-1 selective, whereas the (+) enantiomer was selective for D-2 sites labeled with 3H-spiperone. Relatively sedating antidepressants had greater D-1 affinity than their less-sedating, secondary amine congeners.

Behavioral abnormalities induced by frontal cortical and nucleus accumbens lesions

In previous studies, we have demonstrated that in male rats, unilateral right hemisphere lesions of either the frontolateral cortex or the nucleus accumbens (NAS) result in significant postoperative locomotor hyperactivity. In the present study we carried out two experiments to assess whether the production of hyperactivity in response to these two lesions is mediated through a common mechanism. In the first experiment, male Sprague-Dawley rats received either unilateral frontocortical suction and/or unilateral electrolytic lesions of the NAS. Only rats with lesions of the right hemisphere (suction and/or electrolytic) developed locomotor hyperactivity. Similar lesions in the left hemisphere did not result in behavioral changes. While both right cortical and NAS lesions alone produced hyperactivity, there was no additive effect of both lesions. In the second experiment, the effect of cortical lesions on NAS dopaminergic activity was assessed. Male Sprague-Dawley rats received either a right, left or sham frontocortical suction lesion, and were sacrificed 1, 2, and 4 weeks after surgery. Right hemisphere suction lesions produced a significant bilateral increase in NAS and caudate nucleus dopamine turnover (as measured by DOPAC/DA ratio) 4 weeks post-lesion, while similar left hemisphere lesions did not. These findings suggest that lesions in the dorsolateral frontal cortex and NAS may affect locomotor activity through a common mechanism mediated through the NAS.

Increased basic fibroblast growth factor (bFGF) immunoreactivity at the site of focal brain wounds

Basic fibroblast growth factor (bFGF) is a polypeptide found within the CNS with potent effects on the survival and proliferation of CNS glia and endothelial cells, and on the survival and outgrowth of CNS neurons. Immunohistochemical methods were used to examine relative changes in the levels and distribution of bFGF following focal brain injury. Two monospecific antisera to bFGF were used to immunostain intact mature rat brain, and brain in which a focal mechanical lesion had been made in the dorsolateral cerebral cortex one week previously. In the intact brain, staining was localized primarily in neuronal cell bodies, especially in limbic structures. In injured brain, a marked increase of bFGF immunoreactivity was found at the borders of lesions, localized to the dense accumulation of cells, many of which resembled 'reactive' astroglia. Such increases in local bFGF concentrations may contribute to the cascade of cellular changes--including glial and capillary proliferation, and neural sprouting--that follows focal brain injury.

The effect of p-chlorophenylalanine on cerebral metabolism and biogenic amine content of traumatized brain

It was shown previously that focal cortical freezing lesions in rats cause widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere. This was interpreted as reflecting a depression of cortical activity. It was then demonstrated that cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere of a focally injured brain. To find out if the changes in the serotonergic system are of functional importance and mediate the observed changes in LCGU, the effects of the inhibition of 5-HT synthesis with p-chlorophenylalanine (PCPA) on cerebral metabolism and biogenic amine content in injured brain were studied. PCPA in doses up to 300 mg/kg had little, if any, effect on LCGU in intact brain and in doses up to 100 mg/kg did not modify the depressed LCGU in injured brain. In doses of 200 and 300 mg/kg, PCPA selectively increased cortical glucose utilization in the lesioned hemisphere where it was depressed following injury. PCPA decreased 5-HT levels in the cortical and raphe areas of both intact and injured brain in a dose-dependent manner. However, at doses of PCPA ineffective on LCGU (50 and 100 mg/kg), traumatization still resulted in increased 5-HT metabolism. Doses of PCPA that ameliorated the depression of LCGU in injured brain completely prevented increases in both 5-HT and its metabolite 5-hydroxyindoleacetic acid seen following traumatization in untreated animals. These results provide evidence that decreased LCGU in lesioned brain is due to an activation of the serotonergic system by traumatization. The data are in agreement with the postulated inhibitory role of serotonin in the cortex and its involvement in functional alterations associated with injury. They suggest that blockage of this neurotransmitter system may have a potential in the development of novel therapeutic approaches to brain injury.

Lateralized effect of cerebral infarction on spinal fluid monoamine metabolite concentrations in rats

Using a rat model of stroke, we studied the effect of unilateral middle cerebral artery ligation on cerebrospinal fluid monoamine metabolites at different intervals over a 40-day postoperative period. Male Sprague-Dawley rats were divided into four groups: an unoperated control group (n = 9), a sham-operated group (n = 9), a right middle cerebral artery ligation group (n = 10), and a left middle cerebral artery ligation group (n = 10). One hundred microliters of cerebrospinal fluid were collected percutaneously from the cerebellomedullary cistern just before and 5, 20, and 40 days after the surgical procedure. Monoamine metabolites--3-methoxy-4-hydroxyphenylglycol (MHPG), 5-hydroxy-indoleacetic acid (5-HIAA), and homovanillic acid (HVA)--were measured using high-performance liquid chromatography. MHPG concentration in the right lesion group was significantly depleted from control levels 5, 20, and 40 days after surgery. No such depletion was observed in the left lesion rats. Concentration of 5-HIAA was relatively lower at Days 5 and 20 in the right lesion group than in the left lesion group. HVA concentration did not differ among the groups at any time. Our study has demonstrated a differential effect of unilateral ischemia on cerebrospinal fluid neurochemistry in rats dependent on the cerebral hemisphere involved.

Effect of cholinergic deficit induced by ethylcholine aziridinium (AF64A) on noradrenergic and dopaminergic parameters in rat brain

The consequences of reduced cholinergic function on noradrenergic and dopaminergic neurons has been studied in various rat brain areas for a period of up to 28 days following bilateral intracerebroventricular infusion of various doses of ethylcholine aziridinium ion (AF64A; 1-5 nmol/ventricle). This treatment resulted in a dose-dependent, persistent decrease in acetylcholine (ACh) content ranging from 50.3 +/- 6.0% to 76.9 +/- 3.8% when compared to vehicle-injected rats. Concomitantly, there was a transient, dose-dependent decrease (up to 46.7 +/- 6.4%) in norepinephrine (NE) levels in hippocampus, cortex and hypothalamus. Whereas the noradrenergic system recovered fully within 28 days after 1-3 nmol AF64A/ventricle, the decrease in NE levels persisted after 5 nmol/ventricle. In striatum, a small decrease in ACh levels 4 days after AF64A infusion was accompanied by a transient, dose-dependent decrease in the levels of dopamine (DA) and its metabolites dihydroxyphenylacetic acid and homovanillic acid, suggesting a decrease in DA synthesis and release. Dopaminergic function was fully restored within 14 days after all doses of AF64A used. These data suggest that reduction of cholinergic function might have a considerable impact on noradrenergic and dopaminergic neurons, causing an increase in NE release as well as depression of dopaminergic function.

Effect of cholinergic deficit induced by ethylcholine aziridinium on serotonergic parameters in rat brain

The consequence of loss of cholinergic input on the function of serotonergic neurons has been studied in rat brain after bilateral intracerebroventricular injections of various doses of the cholinotoxin ethylcholine aziridinium ion (1 to 5 nmoles/ventricle). This treatment resulted in a dose-dependent decrease in acetylcholine content in hippocampus, which occurred 2 days after injection and persisted during the 28 day observation period. The reduction in acetylcholine content ranged from 50.3 +/- 6.0% to 76.9 +/- 3.8% when compared to vehicle-injected rats. Other brain areas, including cortex, striatum and hypothalamus, showed only minor and transient changes in acetylcholine levels. Treatment with ethylcholine aziridinium was accompanied by a dose-dependent response of serotonergic neurons. The predominant reaction, which we observed in all areas studied, was an initial increase in 5-hydroxyindoleacetic acid content, a decrease in serotonin content, and consequently an increase in the molar ratio of metabolite/amine, indicating an increase in serotonin turnover. As with acetylcholine, the decrease in serotonin content was most pronounced in the hippocampus, ranged from 19.4 +/- 2.9% to 53.4 +/- 4.1%, and even persisted at 28 days after injection of 3 and 5 nmoles of the toxin/ventricle, although serotonin levels returned towards normal at that time point after injection of 1 or 2 nmoles of the toxin/ventricle. These data suggest that, in the rat, withdrawal of cholinergic input to the hippocampus might have a considerable impact on serotonergic function. This includes an initial increase in activity and, as cholinergic degeneration progresses, a decrease in serotonergic function. The most likely explanation for the serotonergic deficit is that it may reflect adaptation of these neurons to the withdrawal of cholinergic input. Such a phenomenon might help to increase our understanding of the events taking place in the brains of patients with Alzheimer's disease as the cholinergic system starts to degenerate.

Depression influences intellectual impairment in stroke patients

Patients with ischaemic lesions of the left cerebral hemisphere were examined for depression and intellectual impairment: in non-depressed patients, the severity of impairment was related to both lesion volume and location, as assessed by CT scan analysis. Cognitive impairment in patients with major depression was greater than predicted by lesion volume alone, and when patients were matched for severity of impairment, depressed patients had smaller lesion volumes than the non-depressed. After six months, non-depressed patients had significantly less cognitive impairment than depressed patients who showed no improvement. Both depression and lesion volume were significantly and independently related to cognitive impairment. These findings suggest that post-stroke depression can produce a true dementia in its own right, and that treatment of post-stroke depression might benefit cognitive function.

Late changes in cerebral monoamine metabolism following focal ventrolateral cerebrocortical lesions in rats

Twelve weeks after focal ventrolateral cerebrocortical suction lesions (ca. 12 X 4 mm) were made in rats, concentrations of the monoamines norepinephrine (NE), dopamine (DA), and serotonin (5-HT) and their metabolites were measured in several cortical and subcortical brain regions using high performance liquid chromatography with electrochemical detection. Widespread changes in the concentrations of monoamines, their metabolites, and metabolite:monoamine ratios were found in the hemisphere ipsilateral to unilateral (right) lesions, and bilaterally in animals with bilateral lesions. NE was decreased in undamaged dorsolateral cortex and hippocampus, and tended to be increased in striatum and midbrain ipsilateral to lesions. DA was increased in the hypothalamus of bilaterally lesioned animals, and also tended to be increased in striatum and midbrain. The changes of greatest magnitude and anatomical extent were found in the serotonin system: 5-HT was generally increased, and its metabolite 5-hydroxyindoleacetic acid (5-HIAA) and the 5-HIAA:5-HT ratio were decreased throughout the cerebral hemispheres ipsilateral to lesions. These widespread changes in cerebral 5-HT metabolism were qualitatively different and smaller than those previously found at 6 days after cortical lesions, and suggest a biphasic response of the ipsilateral 5-HT system to ventrolateral cortical injury.

Effects of isomers of apomorphines on dopamine receptors in striatal and limbic tissue of rat brain

The optical isomers of apomorphine (APO) and N-propylnorapomorphine (NPA) were interacted with three biochemical indices of dopamine (DA) receptors in extrapyramidal and limbic preparations of rat brain tissue. There were consistent isomeric preferences for the R(-) configuration of both DA analogs in stimulating adenylate cyclase (D-1 sites) and in competing for high affinity binding of 3H-spiroperidol (D-2 sites) and of 3H-ADTN (DA agonist binding sites) in striatal tissue, with lesser isomeric differences in the limbic tissue. The S(+) apomorphines did not inhibit stimulation of adenylate cyclase by DA. The tendency for greater activity or higher apparent affinity of R(-) apomorphines in striatum may reflect the evidently greater abundance of receptor sites in that region. There were only small regional differences in interactions of the apomorphine isomers with all three receptor sites, except for a strong preference of (-)NPA for striatal D-2 sites. These results do not parallel our recent observations indicating potent and selective antidopaminergic actions of S(+) apomorphines in the rat limbic system. They suggest caution in assuming close parallels between current biochemical and functional, especially behavioral, methods of evaluating dopamine receptors of mammalian brain.

Marked behavioral and biochemical sensitivity to lesion size in the posterior cortex of the rat

Unilateral focal cortical suction lesions of varying diameter from 0.7 to 2.0 mm were made in the right posterior lateral cortex of rats. Only the 1.0 mm lesion size resulted in spontaneous postoperative hyperactivity. This increased activity was accompanied by significant elevations in substantia nigra and caudate nucleus dopamine concentrations. Other lesion sizes did not affect behavior or brain biochemical concentrations in this fashion. These results suggest a functional organization in this area of posterior cortex which affects both neurochemistry and behavior.

Effects of N-substituted phenyltetrahydropyridines on cerebral high-affinity synaptosomal uptake of dopamine and other monoamines in several mammalian species

Effects of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (N-methyl-PTP) and its N-propyl congener (N-propyl-PTP) on the high-affinity uptake of tritiated dopamine (DA), norepinephrine, and serotonin by striatal or cerebral cortical synaptosomes were evaluated in several species (rat, guinea pig, rabbit, calf, and man). Both compounds inhibited uptake of 0.1 microM labeled amines at IC50s of 5-10 microM. Effects of N-methyl-PTP were competitive, reversible, somewhat more potent, and more selective for serotonin than were actions of N-propyl-PTP. Similar effects were found in all species. Neither agent inhibited binding of 3H-labeled spiperone or ADTN to DA receptor sites. 3H-N-methyl-PTP did not appear to be taken up selectively into DA neurons. N-methyl-PTP was highly toxic to the rat in doses that did not alter the metabolism of DA or serotonin in brain. These results, overall, do not provide strong support for the hypothesis that reported neurotoxic actions of N-methyl-PTP are mediated by neuron-specific local transport and intracellular accumulation, or account for species differences in the actions of this toxin, but do suggest interactions with brain monoamine neurons. The actions of the neurotoxic effects of N-methyl-PTP remain unclear.