Depression is a frequent comorbid disorder in Parkinson's disease and may antedate its motor symptoms. However, mechanisms underlying Parkinson's disease-associated depression are unknown and its current medication is insufficient. The aim of the present study was to compare antidepressant-like effects of imipramine, fluoxetine and pramipexole in a model of preclinical stages of Parkinson's disease in rats. 6-Hydroxydopamine was bilaterally injected into the ventrolateral region of the caudate-putamen in rats. This treatment induced moderate decreases in the levels of dopamine and its metabolites in the caudate-putamen, nucleus accumbens and frontal cortex and reduced the density of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra pars compacta and ventral tegmental area. The lesion increased immobility measured in the forced swimming test without influencing locomotor activity. Chronic (13 days) administration of pramipexole (1mg/kg sc/twice a day) reversed prolongation of the immobility time in lesioned animals but did not stimulate their locomotion. Chronic pramipexole activated dopaminergic transmission in the brain structures which might contribute to its effectiveness in the forced swimming test. In contrast, the 13-day administration of imipramine (10mg/kg ip/day) and fluoxetine (10mg/kg ip/day) did not shorten the immobility time in lesioned rats but reduced their locomotion. The present study seems to indicate that already a moderate lesion of dopaminergic neurons induces "depressive-like" behaviour in animals which is reversed by chronic administration of the antiparkinsonian drug, pramipexole.
[Show abstract][Hide abstract] ABSTRACT: There is increasing evidence of prodromal manifestation of neuropsychiatric symptoms in a variety of neurodegenerative diseases such as Parkinson's disease (PD) and Huntington's disease (HD). These affective symptoms may be observed many years before the core diagnostic symptoms of the neurological condition. It is becoming more apparent that depression is a significant modifying factor of the trajectory of disease progression and even treatment outcomes. It is therefore crucial that we understand the potential pathophysiologies related to the primary condition, which could contribute to the development of depression. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signaling system involved in physiological homeostasis and stress response. Disturbances of this system lead to severe hormonal imbalances, and the majority of such patients also present with behavioral deficits and/or mood disorders. Dysregulation of the HPA-axis is also strongly implicated in the pathology of major depressive disorder. Consistent with this, antidepressant drugs, such as the selective serotonin reuptake inhibitors have been shown to alter HPA-axis activity. In this review, we will summarize the current state of knowledge regarding HPA-axis pathology in Alzheimer's, PD and HD, differentiating between prodromal and later stages of disease progression when evidence is available. Both clinical and preclinical evidence will be examined, but we highlight animal model studies as being particularly useful for uncovering novel mechanisms of pathology related to co-morbid mood disorders. Finally, we purpose utilizing the preclinical evidence to better inform prospective, intervention studies.
Frontiers in Psychiatry 03/2015; 6:32. DOI:10.3389/fpsyt.2015.00032
[Show abstract][Hide abstract] ABSTRACT: Our recent study has indicated that a moderate lesion of the mesostriatal and mesolimbic
pathways in rats, modelling preclinical stages of Parkinson’s disease, induces a depressive-
like behaviour which is reversed by chronic treatment with pramipexole. The purpose
of the present study was to examine the role of brain derived neurotrophic factor (BDNF)
signalling in the aforementioned model of depression. Therefore, we investigated the influence
of 6-hydoxydopamine (6-OHDA) administration into the ventral region of the caudateputamen
on mRNA levels of BDNF and tropomyosin-related kinase B (trkB) receptor. The
BDNF and trkB mRNA levels were determined in the nigrostriatal and limbic structures by in
situ hybridization 2 weeks after the operation. Pramipexole (1 mg/kg sc twice a day) and
imipramine (10 mg/kg ip once a day) were injected for 2 weeks. The lesion lowered the
BDNF and trkB mRNA levels in the hippocampus [CA1, CA3 and dentate gyrus (DG)] and
amygdala (basolateral/lateral) as well as the BDNF mRNA content in the habenula (medial/
lateral). The lesion did not influence BDNF and trkB expression in the caudate-putamen,
substantia nigra, nucleus accumbens (shell and core) and ventral tegmental area (VTA).
Chronic imipramine reversed the lesion-induced decreases in BDNF mRNA in the DG.
Chronic pramipexole increased BDNF mRNA, but decreased trkB mRNA in the VTA in
lesioned rats. Furthermore, it reduced BDNF and trkB mRNA expression in the shell and
core of the nucleus accumbens, BDNF mRNA in the amygdala and trkB mRNA in the
caudate-putamen in these animals. The present study indicates that both the 6-OHDAinduced
dopaminergic lesion and chronic pramipexole influence BDNF signalling in limbic
structures, which may be related to their pro-depressive and antidepressant activity in
PLoS ONE 03/2015; 10(3):e0117698. DOI:10.1371/journal.pone.0117698 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Considering that depression is a common non-motor comorbidity of Parkinson's disease and that agmatine is an endogenous neuromodulator that emerges as a potential agent to manage diverse central nervous system disorders, this study investigated the antidepressant-like effect of agmatine in mice intracerebroventricularly (i.c.v.) injected with the dopaminergic neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)). Male C57BL6 mice were treated with agmatine (0.0001, 0.1 or 1 mg/kg) and 60 min later the animals received an i.c.v. injection of MPP(+) (1.8 µg/site). Twenty-four hours after MPP(+) administration, immobility time, anhedonic behavior, and locomotor activity were evaluated in the tail suspension test (TST), splash test, and open field test, respectively. Using Western blot analysis, we investigated the putative modulation of MPP(+) and agmatine on striatal and frontal cortex levels of tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF). MPP(+) increased the immobility time of mice in the TST, as well as induced an anhedonic-like behavior in the splash test, effects which were prevented by pre-treatment with agmatine at the three tested doses. Neither drug, alone or in combination, altered the locomotor activity of mice. I.c.v. administration of MPP(+) increased the striatal immunocontent of TH, an effect prevented by the three tested doses of agmatine. MPP(+) and agmatine did not alter the immunocontent of BDNF in striatum and frontal cortex. These results demonstrate for the first time the antidepressant-like effects of agmatine in an animal model of depressive-like behavior induced by the dopaminergic neurotoxin MPP(+).
Neurotoxicity Research 07/2015; 28(3). DOI:10.1007/s12640-015-9540-1 · 3.54 Impact Factor
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