Alteration of dopaminergic innervation and voluntary movements after long period of thirst in a semi-desert rodent, Meriones shawi: Behavioral and immunohistochemical studies

Long term osmotic stress exposure outcomes on rat dopaminergic innervations and the associated motor behavior

The osmotic stress is a powerful stimulus that elicits profound peripheral and central disturbances. In the mammalian brain, osmotic stress has been associated to several glial and neuronal changes. The lack of data regarding the impact on the dopaminergic system and locomotion led us to investigate the effect of prolonged water deprivation in rat on the midbrain dopaminergic system and locomotor performance by dehydrating rats for one and two weeks. Locomotor activity and tyrosine hydroxylase (TH) expression were assessed using the open field test and immunohistochemistry respectively. Water deprivation was accompanied with a significant increment of TH expression within substantia nigra compacta (SNc) and ventral tegmental area (VTA) gradually as the duration of dehydration increases. While locomotor activity showed the inverse tendency manifested by a drop of crossed boxes number following one and two weeks of water deprivation. Our data suggest a substantial implication of midbrain dopaminergic system in the central response to the osmotic stimuli accompanied with locomotor deficiencies.

Crocus sativus restores dopaminergic and noradrenergic damages induced by lead in Meriones shawi: A possible link with Parkinson's disease

Lead (Pb) is a metal element released into the atmosphere and a major source of environmental contamination. The accumulation and concentration of this metal in a food web may lead to the intoxication of the body, more precisely, the nervous system (NS). In addition, Pb-exposure can cause structural and functional disruption of the NS. Studies have shown that Pb-exposure could be a risk factor in the development of Parkinson's disease (PD). The latter is related to dopaminergic deficiency that may be triggered by genetic and environmental factors such as Pb intoxication. In this study, we have evaluated, in one hand, the neurotoxic effect of Pb (25 mg / kg B.W i.p) for three consecutive days on dopaminergic system and locomotor performance in Merione shawi. In the other hand, the possible restorative potential of C. sativus (CS) (50 mg / kg BW) by oral gavage. The immunohistochemical approach has revealed that Pb-intoxicated Meriones show a significant increase of Tyrosine Hydroxylase (TH) levels within the Substantia Nigra compacta (SNc), Ventral Tegmental Area (VTA), Locus Coeruleus (LC), Dorsal Striatum (DS) and Medial Forebrain Bundle (MFB), unlike the control meriones, a group intoxicated and treated with Crocus sativus hydroethanolic extract (CSHEE) and treated group by CSHEE. Treatment with CSHEE, has shown a real potential to prevent all Pb-induced damages. In fact, restores the TH levels by 92%, 90%, 88%, 90% and 93% in SNc, VTA, LC, DS and MFB respectively, similarly, locomotor activity dysfunction in Pb-intoxicaed meriones was reinstated by 90%. In this study, we have revealed a new pharmacological potential of Crocus sativus that can be used as a neuroprotective product for neurodegenerative disorders, especially, which implying dopaminergic and noradrenergic injuries, like PD, trigged by heavy metals.

Animal Models of Intoxication by Metal Elements: A Focus on Neurobehavioral Injuries

Well-functioning of fundamental life processes and human body required metal elements especially essential elements like copper, zinc, magnesium, etc. However, other elements are very toxic for physiological functions including lead (Pb) and cadmium (Cd). Recently, cumulative investigations have interested in the role of metal elements in neurodegenerative diseases and psychiatric disorders especially anxiety and depression. Models of intoxication have been established to evaluate the neurobehavioral effects of metal element exposure via acute and chronic intoxication by metals levels in rats. This method makes available a means to recognize the association between the element level in water, diet, or serum and psychiatric dysfunctions. It allows also to assess the neurobehavioral injuries of metals in animal models and may provide a new window to understand the role metals play in the development of mood and psychiatric disorders.the role metals play in the development of mood and psychiatric disorders.

Neuroprotective potential of Aloe arborescens against copper induced neurobehavioral features of Parkinson's disease in rat

Copper (Cu) is an important trace element for the organism survival, which ensures the normal functioning of different biosystems. However, excessive levels of this heavy metal are responsible for profound physiological alterations including the central nervous system. Numerous findings sustain the involvement of heavy metals, as an environmental risk factor such as copper (Cu), in the neuropathology of Parkinson's disease (PD) which is a chronic neurodegenerative disorder that principally affects the motor system. The classic and evident symptoms of PD namely rigidity, tardiness of movement, and difficulty with walking, result from progressive dopaminergic neurons death within substantia nigra. Whereas, few pharmacological trials have shown a beneficial role against Cu neurotoxicity, Aloe arborescens is one of the powerful medicinal plants with an array of therapeutic effects. Thus, we aimed through the present study, to evaluate the impact of acute Cu intoxication (10μg/g B.W. i.p) for 3days on the dopaminergic system and locomotor performance, together with the possible restorative effect of oral administration of aqueous extract of Aloe arborescens gel (AEAAG) (200mg/kg B.W.). By means of immunohistochemistry, we noted, in the Cu intoxicated rats, a significant loss of TH (tyrosine hydroxylase) expression within substantia nigra compacta (SNc), ventral tegmental area (VTA) and the subsequent striatal outputs, those alterations were correlated to behavioral abnormalities such as a severe drop of locomotor performance. While AEAAG administration to Cu intoxicated rats showed a noticeable beneficial effect; this potential was featured by a complete recovery of the TH expression and locomotor behavior deficiencies in the intoxicated rats. The present investigation have brought, on the one hand, an experimental evidence of an altered dopaminergic innervations following Cu intoxication and on the other hand, a new pharmacological property of Aloe arborescens that may be used as a neuroprotective plant for neurodegenerative disorders, such as PD, touching the dopaminergic system trigged by heavy metals.

The neuronal basis of copper induced modulation of anxiety state in rat

Recently, studies have provided strong evidence indicating the involvement of trace elements in the physiopathology of psychiatric disorders, particularly anxiety. We aimed, through the present study, to describe the effect of acute exposure to Cu (10mg/kg BW) on anxiety state together with the serotoninergic and dopaminergic systems in rat by means of neurobehavioral tests (elevated plus maze, dark light box) and immunohistochemistry using anti-serotonin (5HT) and anti-tyrosine hydroxylase (TH). Our data report that Cu enhanced 5HT innervation in the dorsal raphe nucleus (DRN) together with a loss of TH expression within the ventral tegmental area (VTA), Substantia nigra compacta (SNc) and their subsequent outputs including the medial forebrain bundle (MFB) and striatum. In the elevated plus maze Cu significantly increased the time and the number of entries into the open arms, and raised the time spent in the Dark Box indicating a clear reduced anxiety state induced by Cu. The present data show for the first time a powerful neuro-modulatory potential of Cu in rat which involves primarily a dysfunction of 5HT and DA neurotransmissions.