Biomedical subjects

M J Guerra

Publications and source records attributed to M J Guerra.

At least 19 recordsLinked to original sources

PubMed2005

Expanded mesencephalic precursors develop into grafts of densely packed dopaminergic neurons that reinnervate the surrounding striatum and induce functional responses in the striatal neurons.

The search for alternative sources of dopaminergic cells, other than primary fetal tissue for transplantation in Parkinson's disease has become a major focus of research. Different methodological approaches have led to generation in vitro of cells expressing DA-cell markers, although these cells are frequently unable to survive for a long time in vivo after transplantation and/or induce functional effects in the host brain. In the present study, we grafted cell aggregates treated with antibodies against fibroblast growth factor 4 into dopaminergic-denervated striata in rats. Furthermore, we grafted cell suspensions from primary mesencephalic fetal tissue. Grafts from expanded precursors were able to survive (at least 3 months postgrafting) and most decreased the lesion-induced ipsiversive rotation. In addition, immunolabeling for tyrosine hydroxylase and/or Fos showed that the grafts reinnervated the surrounding striatal tissue with dopaminergic terminals, and induced the expression of Fos in the striatal neurons of the reinnervated area after administration of amphetamine to the host rat. The number of dopaminergic cells in grafts from expanded precursors inducing rotational recovery was usually lower (1,226+/-314) than that in grafts from primary fetal tissue (1,671+/-122), but they were more densely packed in grafts that were of smaller volume and did not have the characteristic central nondopaminergic area observed in grafts from primary fetal tissue. The results suggest that long-term survival and functional integration into the DA-denervated striatum can be achieved with grafts of expanded mesencephalic precursors.

Adrenergic Agents↗

PubMed2004

Angiotensin II increases differentiation of dopaminergic neurons from mesencephalic precursors via angiotensin type 2 receptors.

In addition to the well-known actions of the humoral renin-angiotensin system, all components of this system are present in many tissues, including the brain, and may play a major role in brain development and differentiation. We investigated the possible effects of angiotensin II on the generation of dopaminergic phenotype neurons from proliferating neurospheres of mesencephalic precursors. We observed immunoreactivity for both angiotensin type 1 and type 2 (AT(1) and AT(2)) receptors in the cell aggregates. Double immunolabeling studies revealed that both receptor types are located in neurons and astrocytes. Interestingly, neurons with a dopaminergic phenotype (i.e. tyrosine hydroxylase activity) showed double labeling for AT(1) and AT(2) receptors although the labeling for AT(2) was more intense. Treatment of the neurospheres with angiotensin II (100 nm) during the differentiation period induced a marked increase (about 400%) in the generation of dopaminergic neurons. This was not affected by treatment with the AT(1) antagonist ZD 7155 but was blocked by treatment with the AT(2) antagonist PD 123319. This suggests that AT(2) receptors mediate the stimulatory effect of angiotensin II on the generation of dopaminergic neurons. Apoptotic cell death studies and bromodeoxyuridine immunohistochemistry indicated that the increase in generation of dopaminergic neurons is not due to increased survival or proliferation of dopaminergic cells during treatment with angiotensin and suggested that angiotensin induces increased differentiation of mesencephalic precursors towards the dopaminergic phenotype. Manipulation of the renin-angiotensin system may be useful for increasing production of dopaminergic neurons for transplantation in Parkinson's disease.

Angiotensin II↗

PubMed2003

Interaction between the noradrenergic and serotonergic systems in locomotor hyperactivity and striatal expression of Fos induced by amphetamine in rats.

It is classically considered that Amphetamine acts by increasing extracellular dopamine levels. However, some data suggest a relevant role of other neurochemical systems. The striatum is of particular interest to the study of this question. We have investigated the involvement of the noradrenergic and serotonergic systems and their possible interaction in the striatal responses to Amphetamine using a double behavioral and immunohistochemical approach (i.e., changes in locomotor activity and striatal expression of Fos). In normal rats, Amphetamine induced locomotor hyperactivity and striatal expression of Fos. Pretreatment with the alpha1-adrenergic-receptor antagonist Prazosin or lesion of the serotonergic system significantly reduced the locomotor hyperactivity and striatal Fos expression induced by Amphetamine. Administration of Prazosin to rats with serotonergic denervation did not produce any further reduction in the Amphetamine-induced locomotor hyperactivity or striatal Fos expression compared with that observed in rats with serotonergic denervation only. Amphetamine did not induce a detectable increase in Fos expression in dopamine-denervated striata, and elicited intense rotation towards the dopamine-denervated side. This suggests that striatal dopamine release is essential in the Amphetamine-induced effects on striatal neurons. However, the noradrenergic system plays an important role, and the serotonergic system is necessary for mediating the effects of the Amphetamine-induced noradrenergic stimulation. Concurrent stimulation of dopaminergic and serotonergic receptors appears necessary to regulate Amphetamine-induced responses in the striatal neurons.

Adrenergic alpha-Antagonists↗

PubMed2001

Mechanisms of the effects of exogenous levodopa on the dopamine-denervated striatum.

The efficacy of exogenous levodopa (L-DOPA) is attributed to its conversion to dopamine by the enzyme aromatic L-amino-acid decarboxylase in striatal dopaminergic terminals. However, there is controversy about the mechanisms underlying the therapeutic and adverse effects of L-DOPA after almost all striatal dopaminergic afferents have disappeared (i.e. in the later stages of Parkinson's disease). After administration of 30mg/kg or 100mg/kg of L-DOPA, rats subjected to unilateral dopaminergic denervation showed intense contraversive rotation and a high density of Fos-immunoreactive nuclei throughout the denervated striatum, with no significant induction of Fos in the intact striatum. Injection of the central aromatic L-amino-acid decarboxylase inhibitor NSD-1015 30min before and 15min after the injection of L-DOPA suppressed the rotational behavior and the striatal induction of Fos. Comparison of results obtained in rats subjected to unilateral and bilateral dopaminergic denervation indicated that the presence of contralateral dopaminergic innervation does not significantly modulate the effects of L-DOPA on the denervated striatum. Serotonergic denervation led to slight and statistically non-significant decrease in the rotational behavior and Fos expression induced by high doses of L-DOPA (100mg/kg) in the dopamine-denervated striatum, but totally suppressed the rotational behavior and Fos expression induced by low doses of L-DOPA (30mg/kg). The present data indicate that the major effects observed after administration of exogenous L-DOPA are not due to a direct action of L-DOPA on dopamine receptors, or to extrastriatal release of dopamine, but to conversion of L-DOPA to dopamine by serotonergic terminals and probably some intrastriatal cells. Given that serotonergic neurons appear to play an important role in the action of L-DOPA in the later stages of Parkinson's disease, strategies targeting the serotonergic system should be considered for the treatment of Parkinson's disease and for combating undesirable side effects of L-DOPA therapy.

Animals↗

PubMed2001

Long-term cortical atrophy after excitotoxic striatal lesion: effects of intrastriatal fetal-striatum grafts and implications for Huntington disease.

It is not currently clear whether the cortical atrophy observed in Huntington disease (HD) is entirely a direct consequence of the disease or at least partially a secondary consequence of striatal atrophy. This is of major importance for evaluating the possible therapeutic value of intrastriatal fetal-striatum grafts in HD. Cresyl violet-stained sections from rats that had received striatal excitotoxic lesions 1 wk or 4 wk previously showed small and statistically nonsignificant decreases in the thickness of cortical layers V and VI, while series from rats lesioned 12 months previously showed marked decreases in the thickness of the whole cortex (approximately 35% decrease), layer V (approximately 45%-50%) and layer VI (approximately 45%-50%), together with marked neuron loss in these layers. In deep layer V and layer VI, Fluoro-Jade staining showed labeled neurons in animals lesioned 1 wk previously, labeled neurons and astrocytes in animals lesioned 4 wk previously, and practically no labeling in animals lesioned 12 months previously. Intracortical injection of Phaseolus vulgaris leucoagglutinin revealed that corticostriatal fibers were practically absent from the lesioned area of striata lesioned 12 months previously. However, rats that received intrastriatal fetal-striatum grafts shortly after the lesion and were killed 12 months later showed a significant reduction in cortical atrophy, and a large number of labeled corticostriatal fibers surrounding and innervating the graft. In addition, a reduction in the number of Fluoro-Jade-labeled cells in the cortex was already apparent at 3 wk post-grafting. Regardless of whether HD has a primary effect on the cortex, the present results suggest that the striatal degeneration caused by HD contributes markedly to the cortical atrophy, and that intrastriatal grafts may ameliorate this secondary component of the cortical degeneration.

Animals↗

PubMed2001

Rat brain cholinergic, dopaminergic, noradrenergic and serotonergic neurons express GABAA receptors derived from the alpha3 subunit.

In order to study the most abundant GABAA receptor subtypes expressed in cholinergic, dopaminergic, noradrenergic and serotonergic neurons (i.e., in neurons of the so-called "global" projection systems), we employed double-immunocytochemical techniques combining the labeling of GABAA receptor alpha1, alpha2 and alpha3 subunit with markers for these cells. Cholinergic neurons in the striatum, habenula, and pedunculo-pontine nucleus were immunonegative for the alpha1 subunit, and most were also alpha2-immunonegative. However, cholinergic neurons in the striatum, septum and pedunculo-pontine nucleus were alpha3 immunopositive. Dopaminergic neurons in the substantia nigra pars compacta were highly immunopositive for the alpha3, and noradrenergic neurons in the locus coeruleus were immunoreactive for the alpha3 and the alpha2-subunit; although neurons of these areas were negative for alpha1. Similarly, serotonergic neurons in raphe also showed a high level of labeling of alpha3, while there was a lack of immunoreactivity for the alpha1-subunit, and only some individual neurons were positive for the alpha2 subunit. As the presence of different alpha-subunits confers specific physiological and pharmacological properties to GABAA receptors, the abundance of receptors containing the alpha3 subunit (and the scarcity of receptor subtypes including the other alpha-subunits studied) may have important implications for the GABAergic regulation of brain "global" or "diffuse" projection systems.

Adrenergic Agents↗

PubMed2000

Fenfluramine-induced increase in preproenkephalin mRNA levels in the striatum: interaction between the serotonergic, glutamatergic, and dopaminergic systems.

Fenfluramine (FE) is a halogenated amphetamine derivative that has been used in the treatment of obesity. It has been suggested that the effects of FE on the striatum are mediated by serotonergic mechanisms. However, several major afferent systems may be involved, and administration of FE may be useful to study interactions between these systems. In this work, the effects of FE on striatopallidal neurons and the possible involvement of the major striatal afferent systems were studied in rats by determination of FE-induced changes in striatal levels of preproenkephalin (PPE) mRNA using in situ hybridization. Injection of FE induced a significant increase (60%) in striatal levels of PPE mRNA. This increase was blocked by pretreatment with the D(1) dopamine receptor antagonist SCH-23390 or with the NMDA glutamate receptor antagonist MK-801, or by lesion of the serotonergic system with 5,7-dihydroxytryptamine or p-chlorophenylalanine. In 6-hydroxydopamine lesioned rats, the lesion-induced increase in PPE mRNA levels was not affected by injection of FE, but was reduced by simultaneous serotonergic deafferentation. The results suggest that the serotonergic, glutamatergic, and dopaminergic system interact to increase striatal PPE mRNA levels after FE administration.

5,7-Dihydroxytryptamine↗

PubMed2000

GABAA receptor subunit expression in intrastriatal ventral mesencephalic transplants.

To compare the expression of GABAA receptor subunits in the normal substantia nigra and in fetal mesencephalic neurons ectopically transplanted into the dopamine-depleted striatum, we have employed single and double immunocytochemical approaches using tyrosine hydroxylase (TH) and alpha 1, alpha 2, alpha 3, and beta 2/3 GABAA receptor subunit specific antibodies. In the substantia nigra, alpha 1 and beta 2/3 GABAA receptor subunits were labeled in processes in the pars compacta (SNc) and, more intensely, in both somata and processes in the pars reticulata (SNr). There was no clear TH and alpha 1 or beta 2/3 colocalization, with the exception of some TH-immunoreactive (-ir) neurons that showed a weak immunoreactivity for beta 2/3. Sections immunolabeled for alpha 2 showed a faint diffuse labeling for this subunit both in the SNr and in the SNc. Scattered somata were immunopositive for alpha 2, and some of them were also TH-ir. The labeling for alpha 3 and TH showed that TH-positive neurons expressed intense alpha 3 immunoreactivity, although some TH-negative somata in the SNr expressed weak alpha 3 immunoreactivity. In the transplants, double immunostaining procedures showed that the labeling for alpha 1 or beta 2/3 appeared particularly concentrated in patches of intensely immunoreactive neuronal processes that surrounded TH-ir cells, but these processes were not TH-ir. In the case of alpha 2, diffuse immunostaining was observed all over the graft, with some scattered positive somata. Only a few of them were also TH positive. Sections immunoreacted for alpha 3 and TH revealed that TH-ir neurons expressed intense alpha 3 immunoreactivity, and that only a few TH-negative neurons were weakly positive for alpha 3. These results show that mesencephalic tissue ectopically grafted into the striatum develops a pattern of GABAA receptor expression similar to that normally expressed in situ, and particularly that the grafted dopaminergic neurons express similar GABAA receptors, including the alpha 3 subunit. This might be due to the similarity of GABAergic afferents to these neurons in the SNc and the graft, or that at the time of transplantation this expression had already been determined.

Animals↗

PubMed1999

Recovery after nigral grafting in 6-hydroxydopamine lesioned rats is due to graft function and not significantly influenced by the remaining ipsilateral or contralateral host dopaminergic system.

The aim of this study was to evaluate whether the recovery observed after grafting of fetal nigral cells in 6-hydroxydopamine lesioned rats is due to the graft itself, and whether the participation of the remaining host dopaminergic system is necessary. The effects of unilateral 6-hydroxydopamine lesion on rotational behavior were not significantly affected by sham grafting or by sham grafting plus repeat ipsilateral lesion, but were suppressed by nigral grafting, and by contralateral lesion. Immunohistochemical and in situ hybridization study of right striata of rats subjected to right-side lesion then right-side sham-grafting, and of right and left striata from rats subjected to right-side lesion then right-side sham-grafting then repeat right-side lesion then left-side lesion, revealed (a) no significant amphetamine-induced Fos activation, (b) marked increases in preproenkephalin mRNA levels, and (c) decreases in preprotachykinin levels, with no significant differences in any of these variables among these three types of striata. After nigral grafting, however, intense Fos expression was observed in the striatum, and preproenkephalin and preproenkephalin mRNA levels returned to normal. This recovery was maintained after subsequent repeat ipsilateral 6-hydroxydopamine lesion followed by contralateral lesion. The results demonstrate that, after dopaminergic denervation, the nigral graft itself is able to induce recovery in the assessed parameters, and that these effects of grafting into striata with maximal unilateral 6-hydroxydopamine lesion are due to graft function, and are not significantly influenced by the remaining ipsilateral or contralateral host dopaminergic system. Additionally, it is interesting to note that bilateral denervation led to changes in striatal preproenkephalin and preproenkephalin mRNA levels similar to those observed after unilateral lesion.

Animals↗

PubMed1999

Striatal dopaminergic afferents concentrate in GDNF-positive patches during development and in developing intrastriatal striatal grafts.

Glial cell line-derived neurotrophic factor (GDNF) has potent trophic action on fetal dopaminergic neurons. We have used a double immunocytochemical approach with antibodies that recognize GDNF and tyroxine hydroxylase (TH) or the phosphoprotein DARPP-32, to study the developmental pattern of their interactions in the rat striatum and in intrastriatal striatal transplants. Postnatally, at one day and also at 1 week, GDNF showed a patchy distribution in the striatum, together with a high level of expression in the lateral striatal border, similar to that observed for the striatal marker DARPP-32 and also for TH. In the adult striatum, there was diffuse, weak immunopositivity for GDNF, together with widespread expression of DARPP-32-positive neurons and TH-immunoreactive (TH-ir) fibers. In 1-week-old intrastriatal striatal transplants, there were some GDNF immunopositive patches within the grafts and although there was not an abundance of TH-positive fibers, the ones that were seen were located in GDNF-positive areas. This was clearly evident in 2-week-old transplants, where TH-ir fibers appeared selectively concentrated in GDNF-positive patches. This pattern was repeated in 3-week-old grafts. In co-transplants of mesencephalic and striatal fetal tissue (in a proportion of 1:4), TH-ir somata were located mainly at the borders of areas that were more strongly immunostained for GDNF, and TH-ir fibers were also abundant in these areas and were found in smaller numbers in regions that were weakly positive for GDNF. These results demonstrate that GDNF-ir is coincident with that for TH and DARPP-32, and suggest that GDNF release by fetal striatal neurons both in normal development and in developing striatal grafts may have not only a trophic but also a tropic influence on TH-ir fibers and may be one of the factors that regulate dopaminergic innervation of the striatum.

Animals↗

PubMed1998

The overall rod performance test in the MPTP-treated-mouse model of Parkinsonism.

We investigated the usefulness of the Overall Rotarod Performance (ORP) test for evaluating overall locomotory ability in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-injected-mouse model of Parkinson's disease (PD). For this procedure, the mice are pretrained on the rotarod and then tested at a series of increasing speeds, recording the time that the animal remains on the rod at each speed; the overall rod performance (ORP) of each animal is then calculated as the area under the curve in a plot of time-on-the-rod against rotation speed. At 15-day intervals, C57BL/6 mice were injected (or sham-injected) with MPTP, with ORP testing 7-10 days after each injection. After the fourth injection (day 45), mice in the treated group showed clearly lower ORP than mice in the control group (70-90% reduction in ORP), and were thus considered effectively lesioned. Subsequently, we investigated the short-term effects of apomorphine and L-DOPA on ORP in MPTP-treated mice. Apomorphine (at 0.5 or 2.5 mg/kg) had no significant effect, while L-DOPA (at 80 but not at 40 mg/kg) caused almost complete short-term recovery of pretreatment ORP. By about 100 days after the last MPTP injection, MPTP-treated mice showed partial long-term recovery of ORP; at this stage the mice were killed for tyrosine hydroxylase (TH) immunohistochemistry studies. TH immunoreactivity in the striatum showed a strong positive correlation with ORP as tested on day 100. We conclude that the ORP test is useful for evaluating motor deficit in MPTP-treated mice, and the effects of subsequent treatments.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1998

Mature intrastriatal striatal grafts revert the changes in the expression of pallidal and thalamic alpha 1, alpha 2 and beta 2/3 GABAA receptor subunit induced by ibotenic acid lesions in the rat striatum.

A between-side comparison of GABAA receptor subunit expression levels in the globus pallidus and anterior-pole motor thalamic nuclei of rats with an ibotenate lesion of the striatum, and rats receiving a fetal striatal graft in the lesioned area was made by using immunocytochemistry with subunit-specific antibodies, at different times post-lesion or different times post-grafting. At 10 days post-lesion, there was already an increase in the labeling of the alpha 1- and beta 2/3-subunits in the globus pallidus, entopeduncular nucleus and ventrolateral nucleus ipsilateral to the lesion when compared with the contralateral side, while there were no significant changes at the level of the ventromedial nucleus. Labeling of the alpha 2-subunit showed a clear increase in the entopeduncular nucleus compared with the contralateral side at 10 days post-lesion. Similar changes were also observed for the different subunits studied at 30 and 120 days after lesioning. Rats with 20-day old transplants of fetal striatal neurons that were implanted in the ibotenate lesioned striatum at 10 days post-lesioning, continued to show changes in the expression of GABAA receptor subunits, albeit at a lower level than those of ibotenate lesioned rats at similar age post-lesion. However, when examining rats with 70-day old transplants, the ibotenate-lesion induced between-side changes were almost completely compensated. These findings suggest a correlation between the maturation of the grafts and their capability to function in reestablishing neuronal circuits as shown by the reduction of changes in GABAergic transmission induced by ibotenate lesions, as indicated by the reversal of changes in GABAA receptor subunit in several areas of the basal ganglia circuit.

Animals↗

PubMed1998

Sprouting of the serotonergic afferents into striatum after selective lesion of the dopaminergic system by MPTP in adult mice.

Neonatal destruction of the nigrostrial dopaminergic (DA) system with 6-hydroxydopamine leads to serotonergic (5-HT) hyperinnervation of the striatum. However, it is not clear whether this occurs in adult animals. We investigated whether serotonergic sprouting occurs in adult mice subjected to bilateral lesion of the DA system by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The effects of the lesion were evaluated using a new rotarod test and immunohistochemistry. One hundred days after the last MPTP lesion, there was a clear bilateral serotonergic hyperinnervation throughout the striatum. Additionally, those mice showing the highest reductions in striatal tyrosine hydroxylase (TH) immunoreactivity and in rotarod performance showed the highest density of serotonergic innervation (116% increase). The functional consequences of this process in Parkinson's disease and secondary parkinsonism remain to be clarified.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1998

Interaction between the serotonergic, dopaminergic, and glutamatergic systems in fenfluramine-induced Fos expression in striatal neurons.

Fenfluramine (FE) is a halogenated amphetamine derivative used in the treatment of obesity and thought to induce serotonin (5-HT) release from nerve terminals and to reduce re-uptake. However, other pathways may also be involved. In this work, the effects of FE on the major striatal afferent systems, and the possible interactions of these systems in FE-induced striatal expression of Fos, were studied by lesion of the serotonergic and/or dopaminergic system and administration of NMDA glutamate (MK-801) or D1 dopamine (SCH-23390) receptor antagonists. Both the D1 and NMDA receptor antagonists suppressed Fos expression in response to FE almost entirely. FE-induced Fos expression was also dramatically reduced 24 h after 6-hydroxydopamine (6-OHDA) lesion of the dopaminergic system. However, the reduction was not so marked after chronic 6-OHDA lesion, probably due to compensatory changes. Chronic (5,7-dihydroxytryptamine injection, 4 weeks before) or acute (p-chlorophenylalanine injection) lesion of the serotonergic system led to a marked reduction in Fos expression in response to FE (decrease of about 50%). After simultaneous chronic lesion of both serotonergic and dopaminergic systems, a considerable number of Fos-positive nuclei were still observed (decrease of about 70% in the dorsal and dorsomedial regions). The FE-induced expression of Fos was almost totally suppressed (decrease of about 95% in the dorsal and dorsomedial regions) after simultaneous acute lesion. Our results indicate that FE-induced striatal expression of Fos is due in large measure to DA release and dopaminergic stimulation of D1 receptors. However, concurrent stimulation of NMDA glutamate receptors also appears to be essential, and 5-HT release (although not indispensable) doubles striatal Fos expression.

Animals↗

PubMed1998

The corticostriatal system mediates the "paradoxical" contraversive rotation but not the striatal hyperexpression of Fos induced by amphetamine early after 6-hydroxydopamine lesion of the nigrostriatal pathway.

In rats with unilateral 6-hydroxydopamine (6-OHDA) lesion of the nigrostriatal pathway, amphetamine produces ipsiversive rotational behavior and activation of Fos in the intact striatum, but practically no activation of Fos in the denervated striatum. However, a seemingly paradoxical contraversive rotation, accompanied by intense striatal Fos activation in the lesioned striatum, has been observed during the first few days postlesion. In the present work, behavioral tests and immunohistochemistry for Fos protein and tyrosine hydroxylase (TH) were combined to study striatal changes 36 h after 6-OHDA lesion and particularly the possible involvement of glutamatergic corticostriatal afferents. Injection of amphetamine (0.5 mg/kg or 5 mg/kg) induced contraversive rotation and strong and evenly distributed Fos expression in the lesioned striatum; in the contralateral striatum, however, Fos density was lower than in nonlesioned rats. Pretreatment with the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist MK-801 (either 0.5 mg/kg or 5 mg/kg) did not significantly affect the hyperexpression of Fos in the lesioned striatum, but suppressed the contraversive rotation. Similarly, rats that were subjected to corticostriatal deafferentation (confirmed by sensory neglect tests) and 6-OHDA lesion (1 week or 3 weeks later) showed no significant reduction in the striatal Fos hyperexpression induced by amphetamine (0.5 mg/kg or 5 mg/kg) and no significant rotational asymmetry. In conclusion, the present results indicate that glutamatergic corticostriatal afferents are essential for the contraversive rotational behavior but not the striatal hyperexpression of Fos observed in response to amphetamine early after 6-OHDA lesion, and suggest that intense dopaminergic stimulation of striatal neurons is sufficient for induction of Fos, but that concurrent glutamatergic stimulation is necessary for the motor response.

Afferent Pathways↗

PubMed1997

An automated rotarod method for quantitative drug-free evaluation of overall motor deficits in rat models of parkinsonism.

A variety of tests have been proposed for evaluation of motor deficits in rat models of hemiparkinsonism. The most widely used test, the "rotational behaviour" test, is based upon motor asymmetry induced by drug administration, leading to problems of sensitization, conditioning and priming. In addition, lesion-induced rotational behaviour is sometimes overcompensated by treatments (grafts) while other deficits are unaffected. However, rotational behaviour is reproducible and easy to quantify. On the contrary, most drug-free tests have proved of limited applicability because of subjective scaling, excessive interaction between the experimenter and animals, motivational effects, excessively complex tasks, etc., making it difficult to compare results from different laboratories. In this paper, we present a rotarod based method for automated drug-free evaluation of overall motor deficits in the rat model of hemiparkinsonism, and for identifying treatment-induced changes. Animals are pre-trained on the rotarod and then tested at a series of increasing rod speeds; from this set of values a unique score for each animal is computed (the overall rotarod performance, ORP) summarizing its performance at different speeds. This value is easy to compute and greatly simplifies statistical comparisons. Major advantages of the test are: (i) it does not require drugs, but is nevertheless highly objective, reproducible and easy to quantify; and (ii) falling of animals from rotating rod seems to depend on a combination of lesion-induced deficits which become more evident when rats are forced to move at faster speeds. Since the test is not based exclusively on motor asymmetry, it may also be useful for characterization of bilaterally lesioned animals, for which drug-induced rotational behaviour tests cannot be used.

Animals↗

PubMed1997

GABA(A) receptor subunit expression in intrastriatal striatal grafts comparison between normal developing striatum and developing striatal grafts.

Expression of the alpha1, alpha2 and beta2/3 GABA(A) receptor subunits in maturing cell-suspension striatal grafts and in normal developing striatum was studied by immunocytochemistry. During normal postnatal development, the alpha1 subunit was present in the striatum only at very low density, while the alpha2 and beta2/3 subunits were present with a patchy distribution, in some patches at high density. Double-staining techniques indicated that DARPP-32 (a marker of striatal projection neurons) was not colocalized with alpha1, but was present in some beta2/3-positive areas and all alpha2-positive areas. In striatal grafts, alpha1 immunoreactivity was first detected 2 weeks post-grafting (p.g.), and by 3-10 weeks p.g. the pattern was similar to that observed in mature grafts (1 year p.g.), in which alpha1-immunopositive patches surrounding DARPP-32-positive (i.e. striatum-like) areas are observed. Alpha2 and beta2/3 immunoreactivity was observed within the first week p.g., and by 3-10 weeks p.g. was similar to that observed in mature grafts (i.e. immunoreactivity throughout the graft but with patches of different intensity). During graft maturation there was a marked decline in alpha2 immunoreactivity in DARPP-32-negative areas, as is observed during normal development of the globus pallidus and ventral pallidum. Interestingly, alpha1- and beta2/3-positive fibers (perhaps mostly dendrites) entered DARPP-32-positive patches from DARPP-32-negative areas. This study indicates that the time course of expression of GABA(A) receptor subunits in grafted striatal neurons, closely matches that of morphological maturation of the transplant, that of the development of functional synaptic activity and that of GABA(A) receptor subunit immunoreactivity in normal developing striatum. Our results also suggest that there are significant interactions between DARPP-32-positive and DARPP-32-negative areas with respect to the expression of GABA(A) receptors, and support the suggestion that miniature 'striatopallidal systems' may develop within grafts; such interactions may be important for the functional integration of striatal grafts with the host brain.

Aging↗

PubMed1997

Effects of lesions of the nigrostriatal pathway and of nigral grafts on striatal serotonergic innervation in adult rats.

Neonatal destruction of the nigrostriatal dopaminergic system leads to serotonergic hyperinnervation of the striatum. However, it is not clear whether this occurs in adult animals. We investigated whether serotonergic sprouting occurs in adult animals, and also studied the effects of prior or subsequent implantation of dopamine-rich intrastriatal grafts. One group of adult rats received maximal 6-hydroxydopamine lesions. Other rats received maximal lesions and intrastriatal grafts 2 months later, or vice versa. The lesioned non-grafted rats showed clear serotonergic hyperinnervation throughout the striatum ipsilateral to the lesion. Intrastriatal grafts did not prevent or revert this serotonergic hyperinnervation, and were themselves densely innervated by serotonergic fibers. Serotonergic neurons usually present in the grafted cell suspension also contributed to the serotonergic innervation of the graft and the surrounding striatum.

Animals↗