Neuronal hypothalamic plasticity in chicken [Elektronische Ressource] : a developmental and pharmacological perspective / von Sallagundala Nagaraja

Sallagundala Nagaraja

Sujets

• Biologie

Informations

• Publié par: humboldt-universitat_zu_berlin
• Publié le: 01 janvier 2007
• Nombre de lectures: 33
• Poids de l'ouvrage: 1 Mo

Extrait

NEURONAL HYPOTHALAMIC PLASTICITY IN CHICKEN: A
DEVELOPMENTAL AND PHARMACOLOGICAL PERSPECTIVE



DISSERTATION


Zur Erlangung des akademischen Grades
doctor rerum naturalium
(Dr. rer. nat.)
im Fach Biologie



eingereicht an
Mathematisch-Naturwissenschaftlichen Fakultät I
der Humboldt-Universität zu Berlin



von
M.Phil Sallagundala Nagaraja
geboren am 07.06.1968 in Bangalore, Indien



Präsident der Humbold-Universität zu Berlin
Prof. Dr. Christoph Markschies


Dekan der Mathematisch-Naturwissenschaftlichen Fakultät I
Prof. Dr. Christian Limberg



Gutachter
1. PD Dr. Barbara Tzschentke
2. Prof. Dr.Oliver Behrend
3. . Heike Tönhardt



Tag der mündlichen Prüfung: 15-03-2007
CONTENTS

SUMMARY..............................................................................................................................1
ZUSAMMENFASSUNG.........................................................................................................3

1 INTRODUCTION ....................................................................................................5
1.1 Thermoregulation......................................................................................................5
1.1.1 Homeothermy: an evolutionary perspective.......................................................5
1.1.2 Operation of thermoregulatory mechanisms ......................................................8
1.1.2.1 Basic mechanisms of the regulatory system8
1.1.2.2 Neuronal mechanisms......................................................................................10
1.1.2.2.1 Role of preoptic area of anterior hypothalamus (PO/AH).......................10
1.1.2.2.2 Paradoxical and inappropriate reactions of thermoregulatory responses in
birds .........................................................................................................10
1.1.2.2.3 Neuronal model.......................................................................................11
1.1.2.2.4 Characterization of thermosensitive neurons in the hypothalamus.........13
1.1.2.2.5 Important conditions for comparison between different investigations ..16
1.1.2.2.6 Cellular Mechanisms of thermosensitivity..............................................16
1.1.3 Early ontogeny of thermoregulation in birds....................................................20
1.2 Neurotransmission and role of Gamma-amino butyric acid (GABA)................23
1.2.1 Classes of GABA receptors..............................................................................24
1.2.1.1 Ionotropic receptors: GABA receptor ...........................................................25 A
1.2.1.2 Metabotropic receptors: GABA .......................................................27 B
1.2.1.2.1 Coupling to G Proteins ............................................................................28
2+1.2.1.2.2 Coupling to Ca Channels......................................................................29
+1.2.1.2.3 Coupling K.........................................................................29
1.2.1.2.4 Coupling to Adenylyl Cyclase.................................................................30
1.2.2 GABA agonists and antagonists.......................................................................31
1.2.2.1 GABA agonist: Muscimol31 A
1.2.2.2 GABA antagonist: Bicuculline32 A
1.2.2.3 GABA agonist: Baclofen................................................................................32 B
1.2.2.4 GABA antagonist: CGP35348........................................................................33 B
1.2.3 Role of GABA in thermoregulation34
1.3 Aim of the present study .........................................................................................36

2 MATERIALS AND METHODS...........................................................................37
2.1 Experimental animals and incubation...................................................................37
2.2 Experimental set up for extracellular recordings.................................................38
2.3 Electrical recordings of single neurons..................................................................40
2.4 Temperature stimulation ........................................................................................42
2.5 Analysing procedure of neuronal thermosensitivity ............................................42
2.6 Protocol of synaptic blockage and application of GABAergic substances
(perfusion solutions) ................................................................................................43
2.7 Statistics....................................................................................................................45

3 RESULTS................................................................................................................46
3.1 Plasticity of chick hypothalamic neurons: influence of age.................................46
3.1.1 Comparison of neuronal thermosensitivity in relation to all age groups
investigated.......................................................................................................47
3.1.2 Distribution of different thermosensitive neurons in relation to sensitivity of
neurons in individual age groups......................................................................48
i3.1.3 Distribution of TC values in all the age groups investigated ...........................50
3.2 Characterization of inherently cold-sensitive neurons under synaptic blockade
with Calcium free ACSF and under the action of GABAergic substances ........56
3.3 Plasticity of chick hypothalamic neurons: effect of the GABAergic substances63
3.3.1 Effect of GABA receptor agonist baclofen on chicken hypothalamic B
thermosensitivity: Series 1 ...............................................................................64
3.3.2 A comprehensive study of the effect of the GABAergic substances: Series 2.67
3.3.2.1 Effect of substances acting upon GABA receptors ........................................67 A
3.3.2.2 receptors71 B
3.3.2.3 Effect of simultaneous application of GABA and GABA receptor agonists A B
and antagonists .................................................................................................73

4 DISCUSSION..........................................................................................................78
4.1 Neuronal hypothalamic thermosensitivity: early postnatal developmental
profile in chicken .....................................................................................................78
4.1.1 Comparison of neuronal hypothalamic thermosensitivity between juvenile and
adult birds and adult mammals.........................................................................86
4.1.2 Thermoregulatory relevance of a high hypothalamic cold-sensitivity in
precocial bird species .......................................................................................87
4.2 Modulatory action of GABAergic substances during thermoregulation ...........92
4.2.1 Effect of GABA agonist on different kinds of neurons with special reference B
to cold-sensitive neurons: Series 1 ...................................................................93
4.2.2 A comprehensive study on the plasticity of hypothalamic neurons: effect of
GABAergic substances: Series 2......................................................................97

5 CONCLUSIONS...................................................................................................104
6 REFERENCES .....................................................................................................106
7 PUBLICATIONS..................................................................................................130
8 LEBENSLAUF131
9 ACKNOWLEDGEMENTS .................................................................................134
10 SELBSTSTÄNDIGKEITSERKLÄRUNG.........................................................136


LIST OF FIGURES
Figure 1: Elements of feedback system......................................................................................9
Figure 2: Model of thermoregulatory integration.....................................................................12
Figure 3: Experimental setup..39
Figure 4: Preoptic region of the anterior hypothalamus ..........................................................40
Figure 5: Signal processing. .....................................................................................................41
Figure 6: Sinusoidal temperature change ................................................................................42
Figure 7: A typical protocol of the sinuses under different actions..........................................43
Figure 8: Influence of age on proportion of warm, cold and temperature insensitive
neurons in relation to all neurons investigated in PO/AH region..............................47
Figure 9: Distribution of TC values of PO/AH neurons in 5 days old chickens. .....................51
Figure 10: Distribution of TC values of PO/AH neurons in 10 days old chickens. ..........