L’implant cochléaire, la neuroprothèse la plus répandue et la plus réussie de nos jours, permet à des sujets sourds profonds de récupérer une perception auditive permettant une compréhension du langage. Bien que les technologies et les processeurs actuels aient grandement évoluées depuis ces vingt dernières années, la stratégie optimale pour coder l'intensité sonore dans l’implant n’a pas encore été trouvée. L'accès à des indices physiologiques est difficile chez le patient humain alors qu’il est relativement simple chez l’animal. Le but de cette thèse était de développer un modèle animal (cobaye) d'implantation cochléaire et d'étudier la réponse du système auditif à différentes stratégies de stimulation. Les réponses du nerf auditif et des neurones du cortex auditif primaire ont été obtenues lors de stimulations via un implant cochléaire simplifié.Nous avons observé que l’importante variabilité inter-individuelle dans l’efficacité de 2 stratégies (augmentation d’amplitude vs. de durée des pulses électriques) à augmenter les réponses du nerf auditif se répercute au niveau du cortex auditif. Les tests de nouvelles formes de pulses (pulses asymétriques ou en rampes) sur les réponses des neurones corticaux suggèrent que ce type de pulses permettrait de réduire l’étendue corticale activée par la stimulation électrique même aux charges les plus élevées. Là aussi, une importante variabilité inter-individuelle a été observée. Cela a conduit à ce que les activations corticales les plus proches de l’activation normalement observée par des sons purs, soient obtenues soit avec une forme de pulses soit une autre. Cette thèse prône donc qu’il est indispensable d’avoir accès à de nombreuses stratégies de stimulation sur chaque sujet afin de choisir celle la plus adaptée pour un patient donné. / Cochlear implant, the most successful neuroprosthesis allows deaf subjects to recover auditory perception and speech intelligibility. Over the last decades, the technology and the coding strategies in cochlear implants have been largely improved but the optimal strategy for coding loudness is still problematic. Human studies face a lot of restrictions especially regarding the collection of electrophysiological events. The primary goal of this thesis is to develop an animal model (guinea pig) of implantation and to study the auditory system's responses for different strategies for coding sound loudness (increase in amplitude vs. duration of electrical pulses). We studied the responses of the auditory nerve and primary auditory cortex obtained with electrical stimulation delivered through a simplified cochlear implant.We observed that the large inter-individual variability in the efficacy of these two classical strategies for increasing auditory nerve responses is reflected in the auditory cortex. Testing new forms of pulses (asymmetric pulses or ramped pulses) suggests that this type of pulses would reduce the evoked responses of cortical neurons even at the highest injected charges. Again, a large inter-individual variability was observed. As a consequence, for each animal, the cortical response the closest from the activation normally observed with pure tones, is obtained either with one form of pulses or another. This thesis advocates that it is essential to have access to several stimulation strategies on each subject in order to choose the most appropriate for a given patient.

Bc. Natálie Lupienská: Nonverbal behaviour of elderly people during animal-assisted activity Abstract The aim of the study is to compare nonverbal behaviour of elderly people in three studied interactions: 1) with a therapeutic animal, specifically guinea-pig (Cavia aperea porcellus), 2) with a plush guinea-pig toy and 3) with an ordinary single-coloured cup. Twenty one elderly people (3 men and 18 women, average age of 85 years, SD 7,95 y) participated in the study. All data used for the purpose of the study (video recordings) were collected in a Prague residential house for elderly people in summer 2009. An ethogram composed of sixty elements was prepared. Consequently the Interact software was used for coding of those elements. The inter-subject comparison demonstrated that a guinea-pig significantly enhances an interest in an object and tactile behaviour of observed people. There was no significant difference between the three examined situations in terms of respondent's communication with a therapist, facial expressions or the overall activity. Keywords: nonverbal behaviour, animal-assisted activity, elderly, guinea-pig

To determine the origin of non-vagal afferent fibers innervating the heart of guinea pigs, capsaicin was injected into the ventricular myocardium to induce depletion of substance P (SP). The lower cervical, upper thoracic and lumbar spinal ganglia, as well as the left atrium and base of ventricles, were assayed for SP depletion by using the enzyme-linked immunosorbent assay (ELISA) and immunohistochemical procedures. Capsaicin affected spinal ganglia from the 3 regions differently. The substance P level in lumbar spinal ganglia remained fairly constant, while the level of SP from cervical and thoracic regions declined significantly. At the maximal depletion dosage (173 μg of capsaicin/kg), SP concentration decreased 72.3% in cervical spinal ganglia, 45.5% in thoracic ganglia and 56.1% in the atrium. The lack of SP depletion in lumbar ganglia indicates that capsaicin acted locally on cardiac afferents rather than systemically. Data from this study suggest that capsaicin-sensitive neurons of the heart have cell bodies in the lower cervical spinal ganglia as well as in the upper thoracic spinal ganglia.

Substance P (SP) evokes bradycardia that is mediated by cholinergic neurons in experiments with isolated guinea pig hearts. This project investigates the negative chronotropic action of SP in vivo. Guinea pigs were anesthetized with urethane, vagotomized and artificially respired. Using this model, IV injection of SP (32 nmol/kg/50 μl saline) caused a brief decrease in heart rate (-30 ± 3 beats/min from a baseline of 256 ± 4 beats/min, n = 27) and a long-lasting decrease in blood pressure (-28 ± 2 mmHg from baseline of 51 ± 5 mmHg, n = 27). The negative chronotropic response to SP was attenuated by muscarinic receptor blockade with atropine (-29 ± 9 beats/min before vs -8 ± 2 beats/min after treatment, P = 0.0204, n = 5) and augmented by inhibition of cholinesterases with physostigmine (-23 ± 6 beats/min before versus -74 ± 20 beats/min after treatment, P = 0.0250, n = 5). Ganglion blockade with chlorisondamine did not diminish the negative chronotropic response to SP. In another series of experiments, animals were anesthetized with sodium pentobarbital or urethane and studied with or without vagotomy. Neither anesthetic nor vagotomy had a significant effect on the negative chronotropic response to SP (F3,24 = 1.97, P = 0.2198). Comparison of responses to 640 nmol/kg nitroprusside and 32 nmol/kg SP demonstrated that the bradycardic effect of SP occurs independent of vasodilation. These results suggest that SP can evoke bradycardia in vivo through stimulation of postganglionic cholinergic neurons. Copyright (C) 1999 Elsevier Science Inc.

Effects of spantide ([D-Arg1,D-Trp7,9,Leu11]substance P) on coronary resistance vessels were studied in isolated guinea pig hearts perfused at constant rate with isotonic buffer containing 20 or 40 mM KCl. Spantide (1 μM) caused a 20-fold rightward shift of the substance P (SP) dose-response curve for vasodilation with no change in maximum (KB=5.3×10-8 M). Bolus injections of 0.25 to 250 pmol spantide had no effect, but higher doses caused a brief vasodilation followed by a larger, more prolonged vasoconstriction. Histamine produced similar changes in perfusion pressure. Antihistamines (H1 and H2) reduced or blocked responses to spantide and histamine. These findings indicate spantide is a competitive antagonist to SP in guinea pig coronary resistance vessels. In addition, high doses of spantide can cause prominent vascular effects which are mediated by histamine.

The parmacological effects of guinea pig vasoactive intestinal peptide (VIP) were studied in isolated perfused guinea pig hearts. Bolus injections of VIP produced a dose-dependent tachycardia that was not affected by atenolol. A decrease in amplitude of ventricular contractions occurred in response to all doses of VIP. This response was preceded by a small increase in amplitude in 3 of 6 hearts at the highest dose. VIP produced a decrease in perfusion pressure which was prominent after coronary tone was elevated with [Arg8]-vasopressin. The present findings support speculation that VIP may have a role in the regulation of heart rate and coronary blood flow.

The presence of vasoactive intestinal polypeptide (VIP) has been analyzed in fibers and neurons within the guinea pig intrinsic cardiac ganglia and in fibers innervating cardiac tissues. In whole-mount preparations, VIP-immunoreactive (IR) fibers were present in about 70% of the cardiac ganglia. VIP was co-localized with neuronal nitric oxide synthase (nNOS) in fibers innervating the intrinsic ganglia but was not present in fibers immunoreactive for pituitary adenylate cyclase-activating polypeptide, choline acetyltransferase (ChAT), tyrosine hydroxylase, or substance P. A small number of the intrinsic ChAT-IR cardiac ganglia neurons (approximately 3%) exhibited VIP immunoreactivity. These few VIP-IR cardiac neurons also exhibited nNOS immunoreactivity. After explant culture for 72 h, the intraganglionic VIP-IR fibers degenerated, indicating that they were axons of neurons located outside the heart. In cardiac tissue sections, VIP-IR fibers were present primarily in the atria and in perivascular connective tissue, with the overall abundance being low. VIP-IR fibers were notably sparse in the sinus node and conducting system and generally absent in the ventricular myocardium. Virtually all VIP-IR fibers in tissue sections exhibited immunoreactivity to nNOS. A few VIP-IR fibers, primarily those located within the atrial myocardium, were immunoreactive for both nNOS and ChAT indicating they were derived from intrinsic cardiac neurons. We suggest that, in the guinea pig, the majority of intraganglionic and cardiac tissue VTP-IR fibers originate outside of the heart. These extrinsic VIP-IR fibers are also immunoreactive for nNOS and therefore most likely are a component of the afferent fibers derived from the vagal sensory ganglia.

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no / Introduction: Potential-sensitive dyes have primarily been used to optically record action potentials (APs) in whole heart tissue. Using these dyes to record drug-induced changes in AP morphology of isolated cardiac myocytes could provide an opportunity to develop medium throughout assays for the pharmaceutical industry. Ideally, this requires that the dye has a consistent and rapid response to membrane potential, is insensitive to movement, and does not itself affect AP morphology. Materials and methods: We recorded the AP from isolated adult guinea-pig ventricular myocytes optically using di-8-ANEPPS in a single-excitation dual-emission ratiometric system, either separately in electrically field stimulated myocytes, or simultaneously with an electrical AP recorded with a patch electrode in the whole-cell bridge mode. The ratio of di-8-ANEPPS fluorescence signal was calibrated against membrane potential using a switch-clamp to voltage clamp the myocyte. Results: Our data show that the ratio of the optical signals emitted at 560/620 nm is linearly related to voltage over the voltage range of an AP, producing a change in ratio of 7.5% per 100mV, is unaffected by cell movement and is identical to the AP recorded simultaneously with a patch electrode. However, the APD90 recorded optically in myocytes loaded with di-8-ANEPPS was significantly longer than in unloaded myocytes recorded with a patch electrode (355.6 ± 13.5 vs. 296.2 ± 16.2ms; p< 0.01). Despite this effect, the apparent IC50 for cisapride, which prolongs the AP by blocking IKr, was not significantly different whether determined optically or with a patch electrode (91 ± 46 vs. 81 ± 20 nM). Discussion: These data show that the optical AP recorded ratiometrically using di-8- ANEPPS from a single ventricular myocyte accurately follows the action potential morphology. This technique can be used to estimate the AP prolonging effects of a compound, although di-8-ANEPPS itself prolongs APD90. Optical dyes require less technical skills and are less invasive than conventional electrophysiological techniques and, when coupled to ventricular myocytes, decreases animal usage and facilitates higher throughput assays.

No description available.