Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 7 uppsatser.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 6 uppsatser.

Principal neurons of the medial superior olive (MSO) encode low-frequency sound localization cues by comparing the relative arrival time of sound to the two ears. In mammals, MSO neurons display biophysical specializations, such as voltage-gated sodium (Na[subscript v]) and potassium (K[subscript v]) channels that enable them to detect these cues with microsecond precision. In this dissertation electrophysiological techniques were used to examine the specific channel properties and functional role these channels play in MSO neurons following hearing onset. In addition, computational models that incorporated these physiological data were used to further study how the specific properties of these channels facilitate MSO function. Experiments in this dissertation showed that Na[subscript v] channels are heavily expressed in the persisomatic region of MSO neurons, but unlike those expressed in other neurons they minimally contribute to action potential generation. This is likely due to the low percentage of channels available for activation at the resting membrane potential. Current clamp recordings determined that Na[subscript v] channels counterbalance K[subscript v] channels voltage rectification by boosting near action potential threshold excitatory post-synaptic potentials (EPSPs). Further, computational modeling revealed that synaptic inputs are larger at the soma with Na[subscript v] channels restricted to the soma than when they are evenly distributed throughout the soma and dendrites. During the first few weeks after hearing onset current clamp experiments showed EPSP duration decreased while the temporal resolution for detecting the arrival time of synaptic inputs increased. These changes in EPSP duration are due in part to both the development of faster membrane response properties and increases in the expression of low voltage-activated K[subscript v] channels (K[subscript LVA]). Further investigation determined these channels display a somatically enriched distribution and act to counterbalance the distortions that result from dendritic cable filtering. This is accomplished by K[subscript LVA] actively decreasing the duration of EPSPs in a voltage dependent manner. Computational modeling confirmed these results as well as illustrating their effects on the integration of mono- versus bilateral excitation. Together these findings indicate that the expression of specialized Na[subscript v] and K[subscript v] channels facilitate the neuron’s computational task, detecting and comparing the relative timing of synaptic inputs used in low frequency sound localization. / text

published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

The effects of anaesthetic applications of isoflurane on 82 CA₁ neurons were studied in in vitro preparations (guinea pigs) using intracellular recording techniques. Various parameters of their excitability such as membrane electrical properties, action potentials and their afterhyperpolarizing potentials as well as synaptic transmission were determined during bath perfusion of clinically relevant concentrtaions of isoflurane. Concentrations of isoflurane were detected in the bath with ¹⁹fluorine nuclear magnetic resonance techniques, and were found to range between 0.02 and 0.3 mM. No consistent effects on the membrane properties were observed. When synaptic activity was blocked by tetrodotoxin, isoflurane induced a hyperpolarization (3-5 mV) without affecting input conductance which was computed from the voltage responses to injections of hyperpolarizing current pulses and the slopes of current-voltage relations for each cell. Responses to depolarizing pulses revealed that the threshold, amplitude and duration of the evoked spikes were not greatly altered, although repetitive spike firing was suppressed in a dose-dependent manner by isoflurane. Similarly, the amplitude and duration of the long-lasting hyperpolarizations following the elicitation of multiple (4 or 5) spikes were reduced in a reversible and dose-dependent manner. Reductions in amplitude and duration of excitatory and inhibitory postsynaptic potentials evoked by electrical stimulation of stratum radiatum were observed; these effects also were strictly dependent on the dose, as well as on duration of the application. These investigations have revealed that isoflurane interferes with synaptic transmission in the hippocampal slice preparation and suggest that presynaptic actions on transmitter release, in addition to postsynaptic effects / Medicine, Faculty of / Anesthesiology, Pharmacology and Therapeutics, Department of / Graduate

No description available.

The electrophysiological and morphological properties of small networks of mammalian neurons were investigated with mouse spinal cord monolayer cultures of 2 mm diameter grown on multimicroelectrode plates (MMEPs). Such cultures were viewed microscopically and their activity simultaneously recorded from 2 of any 36 fixed recording sites. The specific aims achieved were: development of techniques for production of functional MMEPs and maintenance of mini-cultures, characterization of the spontaneous activity of mini-cultures, application of inhibitory and disinhibitory agents, development of staining methods for cultured neurons and initial light microscopic analysis with correlation of electrophysiological and morphological characteristics.

The purpose of this study was to determine if resistance exercise altered peripheral BDNF concentration. Eighteen trained male subjects were split into two groups performing varied repetition ranges. DUP-HR and DUP-LR groups trained 3x/week for 8 weeks, and were equated for total volume (repetitions X sets X intensity). Plasma BDNF and interleukin-6 (IL-6) levels were measured prior to and immediately following the first exercise session of weeks 1, 2, 4 and 6. Pre-exercise levels were also assessed prior to the second and third sessions of week 1 and 6. Lastly, resting levels were measured before and after training intervention. No group differences (p>0.05) were detected for either biomarker. An acute BDNF elevation (p=0.018) was detected only in the final week of training. IL-6 elevations were detected at all acute measurements (p<0.01). BDNF and IL-6 percentage change correlated significantly (p<0.05) in week-1. No chronic alterations were observed (p>0.05). / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2015 / FAU Electronic Theses and Dissertations Collection

BDNF is a neurotrophin that enhances neural health and is increased by exercise. PURPOSE: To compare moderate continuous (MCE) and high-intensity interval exercise (HIE) effects on serum BDNF levels, and examine the relationship between BDNF and lactate. METHODS: Seven males completed a VO2peak test and two protocols on separate days, (MCE) 28 min at 60% Workrate max (WRmax) and (HIE) 28 min of intervals at 90%WRmax (10- 1 min intervals separated by 2 min of rest). Serum BDNF and lactate were determined prior, during, and following both protocols. RESULTS: BDNF levels (pg/mL) increased from baseline during HIE and MCE (p<.05). The BDNF response to HIE correlated with lactate for area under the curve (AUC) (r=0.901; P<0.05). CONCLUSION: HIE is an effective alternative to MCE at increasing BDNF. Additionally, lactate may act as a measure of intensity or a mediator of the BDNF response to exercise. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Bibliography : leaves 154-163 / ix, 163 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, and Mathematical Physics, 1993