Beta-adrenergic signal transduction in the hypothalamus of the European hamster: Relation with the seasonal hibernation cycle and the diurnal activity cycle

• Published in: Biology of the cell 1997-11, Vol.89 (8), p.525-529
• Main Authors: Pleschka, Klaus, Nürnberger, Frank
• Format: Article
• Language: English
• Subjects: 1-Methyl-3-isobutylxanthine - pharmacology; adenylyl cyclase; Adenylyl Cyclases - physiology; Adrenergic beta-Agonists - pharmacology; Adrenergic beta-Antagonists - pharmacology; Animals; Arousal - physiology; Chlorides - pharmacology; Circadian Rhythm - drug effects; Circadian Rhythm - physiology; Circadian Rhythm - radiation effects; Colforsin - pharmacology; Cricetinae - physiology; Cyclic AMP - biosynthesis; Enzyme Activation - drug effects; European hamster ( Cricetus cricetus); Guanylyl Imidodiphosphate - pharmacology; hibernation; Hibernation - drug effects; Hibernation - physiology; Hibernation - radiation effects; Hypothalamus - drug effects; Hypothalamus - physiology; Imidazoles - pharmacology; Light; Male; Manganese Compounds - pharmacology; Propanolamines - pharmacology; Receptors, Adrenergic, beta-1 - drug effects; Receptors, Adrenergic, beta-1 - physiology; Receptors, Adrenergic, beta-2 - drug effects; Receptors, Adrenergic, beta-2 - physiology; Seasons; signal transduction; Signal Transduction - drug effects; Signal Transduction - physiology; β-adrenergic receptors
• ISSN: 0248-4900; 1768-322X
• DOI: 10.1016/S0248-4900(98)80008-7

Mammalian hibernation, an adaptation to survive harsh winter conditions, is one of the most prominent seasonal rhythmic processes exactly regulated on a low metabolic level. Diurnal variations in vegetative physiology are missing during hibernation; however, a precisely working diurnal system is mandatory for both the proper initiation and termination of the annual hibernation phase and the periodical arousal reactions. Biorhythms and the vegetative physiological processes connected with hibernation are, among others, controlled by hypothalamic noradrenaline systems. In this study, the density, binding capacity, and relative proportions of β 1- and β 2-adrenergic receptors (AR) within the hypothalamus of: 1) motorically inactive summer; 2) motorically active summer; 3) aroused, motorically active winter; and 4) deeply hibernating winter European hamsters ( Cricetus cricetus) were studied. For further analysis of the β-adrenergic signal transduction cascade, the activity of adenylyl cyclase (AC) was measured by formation of cAMP in controls, after stimulation of G proteins, or after forskolin stimulation without or in presence of manganese ions. While β 1- and β 2-AR subtypes were nearly equally abundant (50% β 1:50% β 2) in active summer, inactive summer, and hibernating hamsters, a significant redistribution in favor of β 2-AR occurred after arousal (40% β 1:60% β 2). The activity of AC was much higher in active summer hamsters than in inactive summer, aroused winter, and hibernating winter hamsters. When AC was stimulated by guanylylimidophosphate [Gpp(NH)p], MnCl 2, forskolin, or by forskolin in presence of MnCl 2 instead of MgCl 2, the potency to stimulate AC was found to show the following rank order: basal < Gpp(NH) p < MnCl 2 ≤ forskolin + MnCl 2 < forskolin.