Behavioural and morphological changes following treatment with GM-1 ganglioside of rats with an electrolytic lesion of the substantia nigra

GM1 ganglioside partially rescues cultured dopaminergic neurons from MPP(+)-induced damage: dependence on initial damage and time of treatment

GM1 ganglioside is believed to be important in promoting the recovery of neurons from injury. The present study assesses the ability of GM1 to repair or prevent the damage of dopamine neurons caused by the neurotoxin 1-methyl-4-phenylpyridinium (MPP+). Treatment of mesencephalic cell cultures with 2.5 microM MPP+ resulted in the loss of 30% of tyrosine hydroxylase (TH) immunoreactive neurons. In contrast, cultures administered 100 microM GM1 ganglioside for 3 days after toxin treatment contained nearly control numbers of TH+ neurons (97%). This reparative effect of GM1 was reflected in parallel increases in TH enzyme activity, dopamine and dopac levels. Cultures sustaining greater insult from higher doses of MPP+ (5.0-10.0 microM) did not benefit from ganglioside treatment, suggesting that rescue by GM1 depended on the degree of initial damage to cells. Moreover, the timing of ganglioside treatment was critical; pretreatment with GM1 alone did not prevent or attenuate the damage caused by subsequent incubation in 2.5 microM MPP+.

Ganglioside GM1 cooperates with brain-derived neurotrophic factor to protect dopaminergic neurons from 6-hydroxydopamine-induced degeneration

Brain-derived neurotrophic factor (BDNF) has recently been shown to enhance the survival of dopaminergic neurons in cultures derived from the embryonic rat mesencephalon. In the present study BDNF was found to protect cultured dopaminergic neurons from injury induced by acute exposure to the dopaminergic-selective neurotoxin 6-hydroxydopamine. The BDNF effect was concentration (ED50 approximately 10 ng/ml) and time-dependent, as determined by tyrosine hydroxylase immunocytochemistry. More importantly, subthreshold amounts of BDNF were rendered efficacious in the presence of ganglioside GM1: loss of tyrosine hydroxylase positive cells was reduced from 80% to only 20%. Thus GM1 may provide a fruitful treatment strategy for disorders of dopamine function such as Parkinson's disease.

Comparison of GM1 ganglioside, AGF2, and D-amphetamine as treatments for spatial reversal and place learning deficits following lesions of the neostriatum

These experiments tested the effectiveness of parenterally administered gangliosides and amphetamine as treatments for spatial learning deficits caused by bilateral lesions of the neostriatum. In Expt. 1, rats were tested postsurgically for 30 days on a shock-avoidance, spatial reversal task. Treatments of gangliosides (GM1 at 30 mg/kg, and AGF2 at 20 mg/kg and 30 mg/kg) and D-amphetamine (2 mg/kg) significantly decreased lesion-induced learning deficits on this task, while treatments of 10 mg/kg AGF2 and the combination of GM1 (30 mg/kg) and D-amphetamine (2 mg/kg) were ineffective. In Expt. 2, rats were given bilateral neostriatal lesions and treated with GM1 (30 mg/kg), AGF2 (20 mg/kg) or D-amphetamine (2 mg/kg) and tested postsurgically for 5 days on a place learning task in the Morris water maze. Only the GM1-treated rats showed a reduction in lesion-induced place learning deficits on this task. Since in both experiments, cell counts near the area of the lesion revealed no differences among any of the brain-damaged groups, it was suggested that the treatments exert their behavioral effects by biochemically activating spared neurons, independent of any ultimate effects they may have on neuronal survival.

Opposite effects of intranigral ibotenic acid and 6-hydroxydopamine on motor behavior and on striatal neuropeptide Y neurons

Unilateral lesions of the basal ganglia circuit induce a disequilibrium of motor processing, most obviously expressed by the resulting circling behavior. Compensatory events, which reduce the motor asymmetry, could be accompanied by changes in neurotransmitter/modulator parameters in the involved brain regions. In the present investigation, the effects of an interruption of the striato-nigro-thalamic loop by ibotenic acid (IBO)-induced lesions of total substantia nigra (SN) on circling behavior and on striatal neuropeptide Y (NPY) neurons were compared with those after the selective destruction of the dopaminergic nigrostriatal projection with 6-hydroxydopamine (6-OHDA). Directly after the operation, IBO-lesioned rats showed a high circling rate to the side contralateral to the lesion, whereas 6-OHDA-lesioned rats showed ipsiversive circling. With the lesion-induced development of dopamine receptor supersensitivity, 6-OHDA-treated rats, when stimulated with the dopaminergic agonist apomorphine, change their circling direction to the contralateral side. Complete IBO lesions of the SN abolished this effect: rats continued to circle to the contralateral side. These observations suggest that not only the dopaminergic denervation of the striatum but also the imbalance in the activity of the thalamo-cortical projection (reduced after 6-OHDA, augmented after IBO) are instrumental in determining the degree and direction of circling. Quantification of NPY-immunoreactive neurons in striatum revealed a decrease in 6-OHDA lesioned rats after 3 days on the side contralateral to the lesion, an effect even more pronounced after 4 month's survival time. IBO-induced lesions of the SN had an opposite effect on NPY-immunoreactivity in the striatum: neuron counts were lower on the ipsi- than on the contralateral side. In addition, a time-dependent variation in total number of NPY-neurons was noted: during the early postoperative periods an increase, followed by a prolonged decrease to values below 50% of the controls after 4 months. Taken together, these results provide evidence that a dopaminergic deafferentation and its consequences on the nigro-thalamo-cortical loop will determine NPY expression in the striatal interneurons. In particular, it is suggested that the number of striatal NPY-neurons and the imbalance in cortical activity are tightly coupled in terms of a negative correlation.

GM1 ganglioside effects on astroglial response in the rat nucleus basalis magnocellularis and its cortical projection areas after electrolytic or ibotenic lesions

We examined the effects of chronic GM1 ganglioside injections on the astroglial response to bilateral electrolytic or ibotenic acid lesions in the nucleus basalis magnocellularis (NBM) within the NBM and in three cortical projection areas of NBM neurons. Glial fibrillary acidic protein (GFAP) immunohistochemistry was used to visualize the reactive astrocytes. Twenty-six days after injury, extensive astrogliosis was observed within the NBM after both types of lesions. An increased number of GFAP-positive cells were found in the cortex of saline-treated rats following electrolytic but not ibotenic lesions. We suggest that the loss of fibers of passage within the lesion area may account for the difference in cortical gliosis following the two types of damage. Although 17 days of GM1 injections did not affect astrocyte morphology within the NBM, ganglioside treatment reduced the number of GFAP-positive cells after electrolytic but not after ibotenic lesions. Within the cortex, a decrease in GFAP immunoreactivity, size, and number of astrocytes was only observed after electrolytic lesion. These data indicate that a decrease in the astroglial response to injury is the result of an interaction between the type of injury (electrolytic lesion) and chronic GM1 treatment.

GM1 ganglioside treatment promotes recovery of electrically-stimulated [3H]dopamine release in striatal slices from rats lesioned with kainic acid

The electrically-evoked release of [3H]dopamine ([3H]DA) from rat striatal slices was studied after a monolateral intrastriatal injection of kainic acid (KA). The release in the KA-lesioned striatum measured 4 days after the lesion was largely reduced (by 80%) with respect to the contralateral striatum. Administration of GM1 ganglioside (GM1) beginning on the day of the lesion resulted in restoration of the catecholamine release. Significant recovery was observed when GM1 was administered i.p. daily at the dose of 3 mg/kg for 6 days. The ganglioside given for 6 days at 30 mg/kg restored to near normal the electrically-evoked [3H]DA release. Similar recovery from the KA-induced injury occurred spontaneously but required 50 days.

Siagoside selectively attenuates morphological and functional striatal impairments induced by transient forebrain ischemia in rats

BACKGROUND AND PURPOSE

Transient forebrain ischemia induced in rats by the four-vessel occlusion method is known to produce severe neural damage in the hippocampus and striatum and a behavioral syndrome the major symptom of which is a working memory deficit. Recent evidence suggests that monosialogangliosides can ameliorate postischemic symptoms. Our purpose was to study the effect of siagoside, the inner ester of GM1 ganglioside, on some behavioral and morphological impairments induced by four-vessel occlusion in rats.

METHODS

Rats were injected daily with 5 mg/kg i.p. siagoside starting 4 hours after the cerebral ischemia. After 14 days the rats were tested for working memory in a water T maze or scored for apomorphine-induced stereotypy. The rats were killed 21 days after the cerebral ischemia. Histological and computer-assisted morphometric analyses were performed on cresyl violet-stained brain sections, which were graded according to a neuropathologic score, and on sections stained with a monoclonal antiserum against dopamine and cyclic adenosine-3',5'-monophosphate-regulated phosphoprotein, a marker for striatal dopaminoceptive neurons.

RESULTS

Siagoside treatment reduced the stereotypy score induced by low doses of apomorphine and the extent of striatal lesions but did not affect the working memory deficit or the extent of hippocampal lesions.

CONCLUSION

Daily siagoside treatment after acute cerebral ischemia attenuates some morphological and functional deficits related to striatal damage. These effects can be interpreted as a selective protective action on striatal neural populations or as a modulatory action on neural systems involved in striatal control. These data are consistent with preliminary clinical reports showing that monosialogangliosides enhance motor recovery after acute ischemic stroke.

MPTP-induced parkinsonism: acceleration of biochemical and behavioral recovery by GM1 ganglioside treatment

The effects of GM1 ganglioside administration on functional recovery and recovery of caudate nucleus dopamine levels have been assessed in cats made parkinsonian by administration of the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Cats made severely parkinsonian by MPTP administration began to show spontaneous functional recovery by the third week after MPTP, as had been observed in previous studies with this model. In contrast, cats with similar initial impairment but which received 3 weeks of GM1 ganglioside treatment (30 mg/kg, i.p. daily) showed an accelerated behavioral recovery, showing significant functional improvement after the first week of GM1 treatment and almost normal function by the end of the third week of treatment. The GM1-treated cats had caudate nucleus dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC), and HVA levels significantly increased above levels measured in saline-treated MPTP control cats. A second group of cats received MPTP only until the first signs of parkinsonism were observed and thus overall had a less severe initial syndrome than the cats described previously. Again, while all cats showed functional recovery over time, the recovery process was accelerated in GM1-treated cats. GM1 treatment also caused a significant increase in caudate dopamine levels in these cats. These results suggest that GM1 ganglioside administration can result in increased dopamine levels even in the heavily denervated striatum and accelerate functional recovery after an MPTP-induced lesion of the nigrostriatal dopamine system in the cat. This suggests that GM1 or other trophic factor therapies may be fruitful treatment strategies for a disorder of nigrostriatal function such as Parkinson's disease.

GM1 ganglioside treatment reduces visual deficits after graded crush of the rat optic nerve

Despite numerous reports of beneficial effects of GM1 ganglioside treatment following brain lesions in animals, the underlying neurobiological mechanism of ganglioside-induced functional restoration is still unclear. In order to obtain a better insight into this question, we have made use of a newly developed animal model of brain injury that would potentially permit us to determine the causal relationship(s) among behavioral and neuroanatomical/neurochemical parameters of restoration of function. Following graded crush of the adult rat optic nerve, we have treated the rats with intraperitoneally injected gangliosides and studied the functional outcome with electrophysiological and behavioral parameters. The electrophysiological recording of the compound action potential (CAP) from excised rat optic nerve revealed a significant loss of CAP throughout the first 2 weeks after the injury. However, when rats were treated daily for 7 days with GM1-gangliosides, the CAP measured 10 days after the crush was significantly larger compared to operated controls without treatment. Thus, GM1 appeared to be capable of delaying or partially preventing retinal ganglion cells or their axons from secondary degeneration. Loss of visual function was also evident on the behavioral level of analysis: when rats with unilateral optic nerve crush were evaluated in a visual orienting paradigm, the rats revealed deficits in their ability to orient towards small, moving visual stimuli. However, within about 2 weeks, the animals recovered spontaneously to near normal performance. Daily treatment with GM1-gangliosides was found to significantly improve outcome, largely due to a reduction of the immediate post-lesion deficit. In a second behavioral experiment we also created graded crush in rats bilaterally and evaluated the animals visual capacities in a two-choice brightness discrimination task. In this task, an initial loss of function was followed by recovery within about 2 weeks, but GM1 treatment was without beneficial effects in this paradigm. It is concluded that GM1 improves outcome after graded crush of the adult rat optic nerve, although it appears that improved function needs to be documented with sufficiently sensitive behavioral assays.

Effects of GM1 ganglioside upon neuronal degeneration during withdrawal from alcohol

In previous studies we demonstrated that chronic alcohol consumption induced hippocampal cell and synapse loss in offset with an increase in the length of granule cell dendrites. In addition we observed that withdrawal after long periods of alcohol intake worsened the degenerative processes and that dendritic alterations were no longer apparent. In an attempt to reverse these structural changes we tested the action of GM1 ganglioside during the withdrawal period as there is evidence that GM1 may enhance neuronal recovery after different kinds of brain lesions. Cell and synaptic quantifications were performed and the branching pattern of the granule cell dendritic arborizations was analysed. The number of dentate granule and CA3 pyramidal cells from GM1-treated animals was found not to be significantly different from that of the alcohol-treated and withdrawal groups. No quantitative changes were found in the number of mossy fiber-CA3 pyramidal cell synapses when the aforementioned groups were compared. Whether the lack of effectiveness of GM1 can be related to the model employed or not is thoroughly discussed.

Dopaminergic dysfunction in neonatal hypothyroidism: differential effects of GM1 ganglioside

The effects of daily treatment with GM1 ganglioside (30 mg/kg s.c.) from birth to day 30, on striatal pre- and postsynaptic markers of the dopaminergic system in euthyroid- and 32 day-old hypothyroid rats were studied. The purpose was to assess whether GM1 could prevent the extensive, hypothyroidism-provoked impairment of dopaminergic neurotransmission. Neonatal administration of GM1 well counteracted the hypothyroidism-related deficits in striatal synaptosomal uptake of [3H]dopamine and in membrane binding of [3H]tyramine, a putative marker for the vesicular carrier of dopamine. In the hypothyroid striatum, the decrease of concentrations of DOPAC and HVA, the loss of [3H]SCH-23,390-labelled D1-receptors and the decrease of basal- or dopamine-stimulated, D1-mediated activity of adenylate cyclase were not prevented by GM1. Although somatic and neurobehavioural aberrations of hypothyroids were not at all or only partially ameliorated, a slight improvement of the thyroid status was suggested by less decreased levels of serum thyroxine (T4) after treatment with GM1. The ganglioside-driven selective recovery of the transport and storage process of [3H]dopamine might result either from a chronically-exerted stimulation by GM1 on the NA/K- and Mg-ATPase activities, thus reflecting on the ATPase-dependent neuronal and vesicular transport processes of dopamine or from a GM1-promoted maturation of the otherwise retarded functionality of dopaminergic nerve endings in the neonatal hypothyroid striatum.