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Chronic Stress Decreases Cerebrovascular Responses During Rat Hindlimb Electrical Stimulation.

ABSTRACT: Repeated stress is one of the major risk factors for cerebrovascular disease, including stroke, and vascular dementia. However, the functional alterations in the cerebral hemodynamic response induced by chronic stress have not been clarified. Here, we investigated the in vivo cerebral hemodynamic changes and accompanying cellular and molecular changes in chronically stressed rats. After 3 weeks of restraint stress, the elicitation of stress was verified by behavioral despair in the forced swimming test and by physical indicators of stress. The evoked changes in the cerebral blood volume and pial artery responses following hindpaw electrical stimulation were measured using optical intrinsic signal imaging. We observed that, compared to the control group, animals under chronic restraint stress exhibited a decreased hemodynamic response, with a smaller pial arterial dilation in the somatosensory cortex during hindpaw electrical stimulation. The effect of chronic restraint stress on vasomodulator enzymes, including neuronal nitric oxide synthase (nNOS) and heme oxygenase-2 (HO-2), was assessed in the somatosensory cortex. Chronic restraint stress downregulated nNOS and HO-2 compared to the control group. In addition, we examined the subtypes of cells that can explain the environmental changes due to the decreased vasomodulators. The expression of parvalbumin in GABAergic interneurons and glutamate receptor-1 in neurons were decreased, whereas the microglial activation was increased. Our results suggest that the chronic stress-induced alterations in cerebral vascular function and the modulations of the cellular expression in the neuro-vasomodulatory system may be crucial contributing factors in the development of various vascular-induced conditions in the brain.

SUBMITTER: Lee S

PROVIDER: S-EPMC4688360 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Chronic Stress Decreases Cerebrovascular Responses During Rat Hindlimb Electrical Stimulation.

Lee Sohee S Kang Bok-Man BM Shin Min-Kyoo MK Min Jiwoong J Heo Chaejeong C Lee Yubu Y Baeg Eunha E Suh Minah M

Frontiers in neuroscience 20151223

Repeated stress is one of the major risk factors for cerebrovascular disease, including stroke, and vascular dementia. However, the functional alterations in the cerebral hemodynamic response induced by chronic stress have not been clarified. Here, we investigated the in vivo cerebral hemodynamic changes and accompanying cellular and molecular changes in chronically stressed rats. After 3 weeks of restraint stress, the elicitation of stress was verified by behavioral despair in the forced swimmi ...[more]

PMID: 26778944

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Project description:Stimulation of the mouse hindlimb via the sciatic nerve was used to induce contractions for 4 hours to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 + 0.1 g/g body weight) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon completion of the study. An immediate-early growth response was present in the EDL (FOS, JUN, ATF3, MAFK) with a similar but attenuated pattern in the soleus. Transcript profiles showed decreased fast fiber specific mRNA (myosin heavy chains 2A, 2B; troponins T3, I; -tropomyosin, m-creatine kinase) and increased slow transcripts (myosin heavy chain slow/1, troponin C, tropomyosin 3) in the EDL. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration or myofiber damage in stimulated vs. control muscles. Several fiber type specific transcription factors (EYA1, TEAD1, NFATc1 and c4, PPARG, PPARGC1 and β, BHLHB2) increased in the EDL along with transcription factors characteristic of embryogenesis (KLF4, SOX17, TCF15, PKNOX1, ELAV). No established in vivo satellite cell markers or the genes activated during our parallel studies of satellite cell proliferation in vitro (CYCLINS A2, B2, C, E1, MyoD) increased in the stimulated muscles. These data indicated that onset of fast to slow phenotype conversion occurred in the EDL within 4 hours of stimulation without satellite cell recruitment or muscle injury but was driven by phenotype specific transcription factors from resident fiber myonuclei including activation of nascent developmental transcriptional programs. Adult male Swiss Webster mice (30-35 g) were anesthetized, a bipolar electrode was implanted adjacent to the sciatic nerve and the hindlimb immobilized. The voltage-force relation was determined to establish supramaximal stimulation conditions and the length-tension relation was determined to set the resting length for maximum twitch tension. Contractions were induced by sciatic nerve stimulation (0.5 msec duration, 2-5 volts). The muscles were allowed to rest 15 minutes for full metabolic recovery at physiologic temperatures. Supramaximal stimulation was applied at a rate of 10 Hz for 4 hours. At the end of each experiment the soleus muscles were carefully dissected and flash frozen in liquid nitrogen for analysis of mRNA expression via microarray analysis. The contralateral, unstimulated Soleus provided a genetically matched, paired control for each specimen.

Project description:Stimulation of the mouse hindlimb via the sciatic nerve was performed for a 4-h period to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 +/- 0.1 g/g body wt) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon study completion. An immediate-early growth response was present in the extensor digitorum longus (EDL) muscle (FOS, JUN, activating transcription factor 3, and musculoaponeurotic fibrosarcoma oncogene) with a similar but attenuated pattern in the soleus muscle. Transcript profiles showed decreased fast fiber-specific mRNA (myosin heavy chains 2A and 2B, fast troponins T(3) and I, alpha-tropomyosin, muscle creatine kinase, and parvalbumin) and increased slow transcripts (myosin heavy chain-1beta/slow, troponin C slow, and tropomyosin 3y) in the EDL versus soleus muscles. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration in stimulated versus control muscles, whereas ultrastructural analysis showed no evidence of myofiber damage after stimulation. Multiple fiber type-specific transcription factors (tea domain family member 1, nuclear factor of activated T cells 1, peroxisome proliferator-activated receptor-gamma coactivator-1alpha and -beta, circadian locomotor output cycles kaput, and hypoxia-inducible factor-1alpha) increased in the EDL along with transcription factors characteristic of embryogenesis (Kruppel-like factor 4; SRY box containing 17; transcription factor 15; PBX/knotted 1 homeobox 1; and embryonic lethal, abnormal vision). No established in vivo satellite cell markers or genes activated in our parallel experiments of satellite cell proliferation in vitro (cyclins A(2), B(2), C, and E(1) and MyoD) were differentially increased in the stimulated muscles. These results indicated that the molecular onset of fast to slow phenotype conversion occurred in the EDL within 4 h of stimulation without injury or satellite cell recruitment. This conversion was associated with the expression of phenotype-specific transcription factors from resident fiber myonuclei, including the activation of nascent developmental transcriptional programs.

Project description:BackgroundSensorimotor beta oscillations are increased in Parkinson's disease (PD) due to the alteration of dopaminergic transmission. This electrophysiological read-out is reported both in patients and in animal models such as the 6-OHDA rat model obtained with unilateral nigral injection of 6-hydroxydopamine (6-OHDA). Current treatments, based on dopaminergic replacement, transiently normalize this pathological beta activity and improve patients' quality of life.ObjectivesWe wanted to assess in vivo whether the abnormal beta oscillations can be correlated with impaired striatal or cortical excitability of the sensorimotor system and modulated by the pharmacological manipulation of the dopaminergic system.MethodsIn the unilateral 6-OHDA rat model and control animals, we used intra-striatal and intra-cortical single-pulse electrical stimulation (SPES) and concurrent local field potentials (LFP) recordings. In the two groups, we quantified basal cortico-striatal excitability from time-resolved spectral analyses of LFP evoked responses induced remotely by intracerebral stimulations. The temporal dependance of cortico-striatal excitability to dopaminergic transmission was further tested using electrophysiological recordings combined with levodopa injection.ResultsLFP evoked responses after striatal stimulation showed a transient reduction of power in a large time-frequency domain in the 6-OHDA group compared to the sham group. This result was specific to the striatum, as no significant difference was observed in cortical LFP evoked responses between the two groups. This impaired striatal excitability in the 6-OHDA group was observed in the striatum at least during the first 3 months after the initial lesion. In addition, the striatum responses to SPES during a levodopa challenge showed a transient potentiation of the decrease of responsiveness in frequencies below 40 Hz.ConclusionThe spectral properties of striatal responses to SPES show high sensitivity to dopaminergic transmission in the unilateral 6-OHDA rat model. We thus propose that this approach could be used in preclinical models as a time-resolved biomarker of impaired dopaminergic transmission capable of monitoring progressive neurodegeneration and/or challenges to drug intake.

Dataset Information

Chronic Stress Decreases Cerebrovascular Responses During Rat Hindlimb Electrical Stimulation.

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Chronic Stress Decreases Cerebrovascular Responses During Rat Hindlimb Electrical Stimulation.

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