Seasonal Changes in the Activity of the Adrenal Medulla of Viscacha (Lagostomus maximus maximus)

HUGO RODRIGUEZ,; VERONICA PALMIRA FILIPPA; ALICIA PENISSI; TERESA FOGAL; SUSANA DOMNGUEZ; RAMON PIEZZI; LUIS SCARDAPANE

ANATOMICAL RECORD

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New York; Año: 2013 vol. 296 p. 1089 - 1095

0003-276X

Animals living in nontropical climates modify their physiology andbehavior to adapt to seasonal environmental changes. Part of this adaptationinvolves the release of catecholamine from sympathetic nerve endingsand the adrenal medulla, which play a major role in regulating energy balance.The aim of this work was to investigate whether adult male viscachasin their natural habitat exhibits structural changes in the adrenal medulladuring the annual seasonal cycle. In August?September, chromaffin granulesrevealed ultrastructural changes suggestive of piecemeal degranulation.Quantitative morphometric analysis by transmission electronmicroscopy showed a significantly lower percentage of resting chromaffingranules and a higher percentage of altered granules and empty containersin August?September (late winter) compared to February?March (latesummer), suggesting an increased secretory process of catecholamines inAugust?September. The mechanism of piecemeal degranulation mightamplify this process, encouraging the adaptive response to winter environmentalconditions. Tissue levels of epinephrine, norepinephrine, and dopamine(analyzed by high-performance liquid chromatography) changedthroughout the year, reaching maximum values in February?March andminimum values in August?September. These results demonstrate morphologicaland biochemical seasonal variations of the adrenal medulla, suggestingthat epinephrine might promote energy mobilization, which allowthe Lagostomus to cope with adverse environmental conditions and thus tosurvive during winter season. Anat Rec, 296:1089?1095, 2013. VC 2013Wiley Periodicals, Inc.