ABSTRACT
To determine the dopamine (DA) content in the striatum and the expression changes of the apoptosis-associated proteins Bad and Bcl-2 in the substantia nigra compacta (SNc) in elderly rats with abnormal behavior. Fifty three Sprague-Dawley rats were divided into three groups: adult, age-motorplus (normal behavior) and aged-motorminus (abnormal behavior) using the hanger test. The DA content in the striatum and the expression of tyrosine hydroxylase (TH), Bad and Bcl-2 in the SNc were measured by HPLC/MS (high performance liquid chromatogram-mass spectra) and Western Blot. (1) The results from the hanger test demonstrated that the scores and latency of aged-motorminus group were lower than the age-motorplus group. (2) Results from HPLC-MS showed that, compared with the age-motorplus and adult group, the content of DA in elderly rat striata decreased significantly, with a statistically significant difference. (3) The Western Blot demonstrated that, compared with the adults, the expression of TH in elderly rats significantly decreased, but the difference was not significant between the aged-motorminus group and the age-motorplus group. Compared with the age-motorplus and the adult group, the expression of Bad increased but Bcl-2 decreased in the aged-motorminus group. The decrease in TH content in the SNc correlated with the aging of rats. The decrease in DA content in the striatum may correlate with the abnormal behavior in elderly rats, which could be ascribed to the variations in Bad and Bcl-2.
Subject(s)
Aging/pathology , Corpus Striatum/metabolism , Dopamine/metabolism , Proto-Oncogene Proteins c-bcl-2/metabolism , Tyrosine 3-Monooxygenase/metabolism , bcl-Associated Death Protein/metabolism , Animals , Behavior, Animal , Muscle Strength , Rats , Rats, Sprague-Dawley , Substantia Nigra/metabolismABSTRACT
To study the relationship between aging and the vulnerability of substantia nigra pars compacta (SNc) tyrosine hydroxylase immunoreactive positive (TH+) dopaminergic (DA) neurons. We determined the number of TH(+) DA neurons in aged rats (24 mon) compared to adult rats (5 mon) using immunohistochemistry and cell counting. Furthermore, the expression of TH mRNA and protein levels in SN was studied by semi-quantitative RT-PCR and Western blotting. A 13.6% loss of neurons was detected in rostral segment of SNc, and the expression of TH mRNA levels was also reduced (P < 0.05), however, no difference was detected in TH protein levels (P > 0.05). These data suggest that expression of TH protein may increase in the existing SNc DA neurons, which may compensate for the partial loss of TH+ DA neurons.
Subject(s)
Aging/metabolism , Dopamine/metabolism , Neurons/metabolism , Substantia Nigra/metabolism , Animals , Cell Count , Male , Models, Animal , Neurons/cytology , RNA, Messenger/metabolism , Rats , Rats, Sprague-Dawley , Substantia Nigra/cytology , Tyrosine 3-Monooxygenase/metabolismABSTRACT
We studied the relationship between aging and the vulnerability of substantia nigra pars compacta (SNc) calbindin-D-28k immunoreactive positive (CB+) dopaminergic (DA) neurons. Immunohistochemistry and cell counting were used to determine the number of CB+ DA neuron in aged rats (24 mon) compared to adult rats (5 mon). Furthermore, the expression of CB mRNA and protein levels in SN was studied by semi-quantitative RT-PCR and Western blotting. An 11% loss of CB+ DA neurons was detected in both the rostral (8.9%) and caudal (1.7%) segments but not in the intermedial segment of SNc in aged rats compared to adult rats (P<0.05). No difference was detected in CB mRNA and protein levels between aged and adult rats (P>0.05). These data suggest that expression levels of CB mRNA and protein may increase in the existing SNc DA neurons, which may compensate for the partial age dependent loss of CB+ DA neurons in the SNc.
Subject(s)
Aging/metabolism , Dopamine/metabolism , Neurons/metabolism , S100 Calcium Binding Protein G/metabolism , Substantia Nigra/metabolism , Animals , Calbindins , Cell Count , Immunohistochemistry , Male , Neurons/cytology , RNA, Messenger/metabolism , Rats , S100 Calcium Binding Protein G/genetics , Substantia Nigra/cytologyABSTRACT
Glial cell line-derived neurotrophic factor (GDNF) exerts its biological effects via a multi-component receptor system including the ligand binding receptor--GDNF family receptor-alpha1 (GFRalpha1) and the signaling receptor--RET tyrosine kinase. Recently, the neural cell adhesion molecule (NCAM) has been identified as an alternative signaling receptor for GDNF. The purpose of this study was to investigate whether NCAM could mediate the protective effect of GDNF on injured dopamine (DA) neurons and to determine which cytoplasmic signal molecule associated with NCAM was activated while GDNF performing this effect. The results showed that the phosphorylation of NCAM-associated Fyn was upregulated with GDNF treatment, and this upregulation was inhibited by pre-treatment with the NCAM function-blocking antibody. Moreover, pre-treatment with the antibody could abolish the effect of GDNF on promoting the neurite outgrowth of these DA neurons, except for the effect of GDNF on promoting the expression of tyrosine hydroxylase (TH) in these DA neurons. These results suggest that NCAM is involved in the promotive effect of GDNF on the neurite outgrowth in lesioned DA neurons, but not involved in the promotive effect of GDNF on TH expression in these neurons.
