Novel acute stressor effects on interscapular brown adipose tissue sympathetic inervation and UCP-1 content in chronically isolated and spontaneously hypertensive rats

Abstract

Interscapular brown adipose tissue (IBAT) is an energy storing organ involved in the maintenance of homeostasis in stress conditions when the balance of energy supplies is disturbed. The major regulator of IBAT activity is the sympathetic nervous system (SNS). Since genetic background is responsible for the individual differences in neuroendocrine stress responsivity, spontaneously hypertensive rats (SHR) that have a genetically increased general sympathetic output are a useful model for studying adaptive processes in stress conditions. Our aim was to test the effect of acute and/or chronic exposure to various stressors (thermal-cold, psychophysical-immobilization and psychosocial-isolation) on IBAT SNS and the metabolic activity in SHR, by measuring the number of monoamine-containing nerve endings and uncoupling protein-1 (UCP-1) content. The obtained results show that the IBAT SNS activity of unstressed SHR was stimulated by the administration of a single acute or chronic stressor and was independent of the duration or type of stressor, while chronic pre-stress of isolation suppressed further the SNS reaction to novel acute stress exposure. The IBAT UCP-1 content followed SNS changes, suggesting that this system is dominant in the regulation of IBAT metabolic rate in SHR.