E-15 Thematic Poster - Neuroscience

May 31, 2013, 9:30 AM - 11:30 AM Room: 208 1887 Chair: Dane B. Cook, FACSM. University of Wisconsin-Madison, Madison, WI. (No relationships reported) 1888 Board #1 May 31, 9:30 AM - 11:30 AM Striatal Enkephalinergic Differences in Rats Selectively Bred for Running Capacity Derek C. Monroe1, Philip V. Holmes1, Lauren G. Koch2, Steven L. Britton2, Rodney K. Dishman, FACSM1. 1University of Georgia, Athens, GA. 2University of Michigan, Ann Arbor, MI. (No relationships reported) Rats selectively bred for high- and low-treadmill running capacity also display different amounts of wheel-running behavior, but whether wheel-running can be explained by intrinsic or adaptive brain mechanisms is not understood. Dopaminergic transmission in mesolimbic brain structures is thought to drive motivated locomotory behavior. Dopamine regulates enkephalin expression in striatal neurons, so an enkephalinergic mechanism may also be involved in motivated running. PURPOSE:To describe intrinsic differences and responses to wheel running in brain ENK between rats bred for high- (HCR) and low- (LCR) treadmill running capacity. METHODS:40 male (20 HCR and 20 LCR) and 40 female (20 HCR and 20 LCR) rats were randomly assigned to 3 weeks of activity wheel or sedentary conditions without wheel access. In situ hybridization histochemistry was used to assess ENK mRNA expression (μCi) in the ventral nucleus accumbens (NA) and the olfactory tubercle (OT). RESULTS:HCR rats ran on average 4-6 times more than LCR rats (p<.001). There was a strain × quadratic trend across time for females (F(1,18) = 10.192, p =.005) and a quadratic trend across time independent of strain for males (F(1,18) = 4.927, p =.040). HCR rats expressed less ENK than LCR rats in the NA among females (F(1,23) = 4.905, p =.037), and in the OT among both females (F(1,23) =13.302, p =.001) and males (F(1,28) = 8.439, p =.007). CONCLUSIONS:Strain differences in ENK expression in the olfactory tubercle, and possibly the ventral accumbens, may partially explain differential wheel-running behavior. Decreased ENK in the ventral striatum may produce a compensatory increase in opioid receptors (Greenwood et al., 2011). Future research is needed to determine whether decreased transmission (lower ENK) or increased transmission (upregulated opioid receptors) is associated with wheel running hedonics. 1889 Board #2 May 31, 9:30 AM - 11:30 AM Increases in White Matter Hyperintensity Volume are not Correlated with Memory Dysfunction in Patients with Amnestic Mild Cognitive Impairment Benjamin Tseng1, Ayaz Khan1, Candace Hill1, Kyle Armstrong1, Kristen Martin-Cook2, Ramon Diaz-Arrastiae3, Myron Weiner2, Munro Cullum2, Hanzhang Lu2, Rong Zhang1. 1Institute for Exercise and Environmental Medicine, Dallas, TX. 2University of Texas Southwestern Medical Center, Dallas, TX. 3Uniformed Services University of the Health Sciences, Dallas, MD. (Sponsor: Benjamin Levine, FACSM) (No relationships reported) Brain white matter hyperintensity (WMH) is a measure of white matter damage which may contribute to cognitive dysfunction in older adults. People with amnestic mild cognitive impairment are at higher risk for Alzheimer’s disease (AD). The relationship between WMH and cognitive impairment in aMCI patients is not clear. PURPOSE:To determine if WMH volume is related to cognitive impairment in patients with aMCI. METHODS:Thirty-three aMCI patients (18 females, age=67±7yrs, clinical dementia rating score=0.5) and 25 age- and education-matched cognitively normal adults (15 females, age=67±7yrs) participated. WMH was assessed using MRI Fluid-Attenuated-Inversion-Recovery (FLAIR) images on a 3T Philips Achieva MR system. Periventricular and deep WMH volumes were quantified and differentiated using semi-automatic programs (MRICro and MatLab). Cognitive function was assessed using standard clinical neuropsychological tests. RESULTS:Both periventricular and deep WMH volumes, normalized to the whole brain volume, were higher in the aMCI group relative to the controls (0.42±0.28 vs. 0.27±0.17, p<0.05, 0.24±0.15 vs. 0.12±0.09, p<0.01, respectively). In addition, MCI patients scored lower in Montreal Cognitive Assessment (25.50±2.19 vs. 27.42±1.68, p<0.01), California Verbal Learning Test in total score (43.74±10.33 vs. 53.37±9.40, p<0.01), short delay recall (8.33±2.50 vs. 11.44±2.71, p<0.01), long delay recall (9.72±2.54 vs. 12.50±2.79, p<0.01), and recognition (13.78±1.56 vs. 14.94±1.51, p<0.05). No significant differences were observed in other cognitive domains. WMH volumes also were not correlated with memory dysfunction in patients with aMCI. CONCLUSION:WMH volume was increased in patients with aMCI. However, increases in WMH volume were not correlated with memory dysfunction. The clinical significance of increases in WMH volume in patients with aMCI merits further investigation. 1890 Board #3 May 31, 9:30 AM - 11:30 AM Cerebral And Muscular Oxygenation During Different Modes Of Exercise Carlos Ugrinowitsch1, Alan St Clair Gibson2, Timothy D. Noakes3, Fabiano Pinheiro1, Carlos A. Anjos4, Roberto Covolan4, Flávio O. Pires5. 1University of Sao Paulo, Sao Paulo, Brazil. 2Northumbria University, NewCastle, United Kingdom. 3University of Cape Town, Cape Town, South Africa. 4State University of Campinas, Campinas, Brazil. 5Catholic University of Brasília, Brasília, Brazil. (No relationships reported) Reductions in cerebral oxygenation (Cox) could limit exercise tolerance during maximal incremental tests (MIT), but not in self-paced exercises, while muscular oxygenation (Mox) does not limit both. Despite never investigated in the same experiment, changes in Cox, but not in Mox, could be related to differences in exercise mode. PURPOSE:To investigate Cox and Mox patterns during a power-controlled exercise (TIM), and power self-paced exercise (i.e. 4km time trial - TT4km). METHODS:9 cyclists (VO2MAX of 52.4 + 6.2 mL.kg-1.min-1) performed a MIT with 25W.min-1 increments until exhaustion, and a TT4km. Power output (PO-watts) was registered at 2Hz. Cox (pre-frontal lobe) and Mox (vastus lateralis) data ([delta] in μM) were recorded at 25Hz using functional Near Infrared Spectroscopy (fNIRS). Oxy-hemoglobin (OHb) and oxy- deoxy-hemoglobin difference (OHb-diff) were used as Cox and Mox indexes. Data were analyzed at 10% time intervals in both exercises (two factors mixed models; P < 0.05). RESULTS:Peak PO was 368.4 + 19.3 W in MIT and 391.9 + 78.7 W in TT4km. Cox OHb and OHb-diff dropped from 70% to 100% (p< 0.05 - *) in both exercise modes. Yet, OHb-diff in TT4km was higher at 10%, but lower at 60% and 80% (p< 0.05 - #) and at 90% (p= 0.07), when compared to MIT. In both exercise modes, Mox (OHb and OHb-diff) dropped up to 60% (p< 0.05 - *), but remained stable thereafter. No exercise mode effect was observed in Mox (MIT × TT4km). CONCLUSION:Cox results could suggest similar “timing of afferent signals” to the brain regardless of the exercise mode. However, higher OHb-diff at the beginning of the TT4km could indicate that Cox is regulated in a feed-forward manner, allowing greater brain deoxygenation during the last 30% of a self-paced exercise. 1891 Board #4 May 31, 9:30 AM - 11:30 AM GDNF’s Expression In Slow- And Fast-twitch Muscle Fibers Are Dependent On Exercise Intensity Amy Gyorkos, John Spitsbergen. Western Michigan University, Kalamazoo, MI. (No relationships reported) Glial cell-line derived neurotrophic factor (GDNF) is the most potent factor for motor neuron survival and supports and maintains the neuromuscular system. GDNF’s expression in skeletal muscle has been shown to be altered following exercise in as little as two weeks. Following low-intensity exercise, GDNF has been shown to increase in slow-twitch skeletal muscle, while decreasing in fast-twitch skeletal muscle. GDNF appears then to be expressed in an activity-dependant manner. PURPOSE:It is our aim to test whether a higher intensity exercise can alter GDNF’s expression in both slow- and fast-twitch muscle fibers. METHODS:Male Sprague-Dawley rats (4 weeks old) were housed individually with a resistance wheel (RW, n=5), a free wheel (FW, n=4), or without a wheel (CON, n=5). The R-RUN group had 120g of resistance added to the wheel for the duration of the study. All wheel running was voluntary and continuously recorded for two weeks. RESULTS:GDNF protein content increased significantly in the recruited fast-twitch Plantaris (PLA) muscles following RW (6.3+1.0, p<0.05) and FW (6.8+2.1, p<0.05) running compared to controls (2.3+0.4,p<0.05). GDNF protein content also increased in the recruited slow-twitch Soleus (SOL) muscles following FW (4.1+0.9, p<0.05) running compared to controls (1.1+0.7, p<0.05). GDNF protein content and the distance traveled was positively correlated in SOL (r=.760, p<0.01, n=14), while GDNF protein content and velocity were positively correlated in PLA (r=.690, p<0.01, n=14) for all groups. CONCLUSION:We show that higher intensity exercise (higher velocity and shorter bouts) can increase GDNF in the recruited fast-twitch muscle fibers. We conclude that regulation of GDNF expression is activity dependent and that the intensity of the exercise can alter its expression differently in slow and fast twitch muscle fibers. This work was supported by NIH grant 1 R15 AG022908-01A2, NSF grant DBI 0552517 and Western Michigan University. 1892 Board #5 May 31, 9:30 AM - 11:30 AM Are The Crossed Responses Found In Human Trapezius Muscles H Reflexes? Steffen Vangsgaard1, Pascal Madeleine1, Janet L. Taylor2. 1Aalborg University, Aalborg, Denmark. 2Neuroscience Research Australia, Sydney, Australia. (No relationships reported) Neck-shoulder disorders are often reported in industrialized countries. This has prompted interest in neural control of the neck-shoulder muscles. Previous findings have described both ipsilateral and unusual crossed H reflexes in the trapezius muscle. PURPOSE:To confirm the presence of crossed H reflexes in trapezius evoked via stimulation of the C3/4 cervical nerves. METHODS:The maximal M wave and H reflex were measured in the ipsilateral trapezius in volunteers (n=10) by percutaneous electrical stimulation of the accessory nerve and the cervical nerves of C3/4 respectively. Repeated stimulation of the C3/4 cervical nerves was performed during 3 different tasks: relaxation, contraction of ipsilateral trapezius, contraction of contralateral trapezius. RESULTS:Stimulation of the accessory nerve evoked M waves at latencies of 2.9±0.2 ms for the upper part, 3.9±0.5 ms for the middle part, and 5.0±0.7 ms for the lower part of the ipsilateral trapezius. Stimulation of the C3/4 cervical nerves during ipsilateral contraction evoked ipsilateral reflexes in the upper (n=8) middle (n=9) and lower (n=7) trapezius with median latencies of 9.05 [8.13; 9.38] ms, 9.9 [9.2; 10.48] ms, and 10.7 [10.01; 11.6] ms respectively These responses increased and decreased significantly with increases and decreases in pre-stimulus electromyographic activity (EMG) in all ipsilateral parts of trapezius. Thus, they were considered H reflexes. Contralaterally, responses with latencies corresponding to those observed ipsilaterally occurred in the upper (n=1), middle (n=9), and lower (n=6) part of trapezius. These potentials which were recorded from the left trapezius increased significantly more with contraction of the right trapezius compared with contraction on the left side. This behaviour is not consistent with H reflexes. CONCLUSION:This study found ipsilateral and contralateral responses consistent with previous findings. However, we conclude that the contralateral response is not a crossed reflex but is more likely to be far field EMG.

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