Regulation des Energiehaushalts von Kleinsäugern unter besonderer Berücksichtigung saisonaler Stoffwechseladaptionen des Dsungarischen Zwerghamsters, Phodopus sungorus.

This work focuses on the regulation and adaptation of energy balance of small mammals and underlines the complexity of regulatory mechanisms which are involved to attain an appropriate energy metabolism, for example in response to changing environmental conditions. This work demonstrates, that these regulatory mechanisms can be found on the level of - gene expression in the periphery: The expression of Myostatin, a hormone negatively regulating muscle mass, is seasonally upregulated. This is associated with low muscle mass in short photoperid by an inhibition of muscle growth and hence contributes to low body mass in times when energy supply is low. - post-translational processing of neuropetides in the central nervous system: Pro-Opiomelanocotin (POMC) processing is photoperiodically regulated by differential expression and protein biosynthesis of the prohormone convertase 2. This is associated with higher levels of anorexigenic POMC cleavage products such as α-MSH und β-Endorphin in short photoperiod. - the endocrine system controlling the oxidation of substrates: Thyronamine, an endogenous derivate of the thyroid hormone, interrupts carbohydrate utilisation which is followed by a compensatory rise in lipid utilisation. - the signalling of the autonomic nervous system: Parasympathetic and sympathetic activities are involved in the generation of ultradian rhythms, which facilitate quick responses of physiological processes to changing environments. Furthermore, an intact signalling of the sympathetic nervous system is required for the display of spontaneous daily torpor. - the signalling of specialized centres of the central nervous system: Deletion of the cannabinoid receptor type 1 in the forebrain leads to a lean phenotype and a resistance to diet-induced obesity. This phenotype results from a decrease in energy absorption and an increased lipid oxidation and thermogensis as a consequence of enhanced sympathetic tone.