Apelin-13 microinjection into the paraventricular nucleus increased sympathetic nerve activity innervating brown adipose tissue in rats

The aim of present study is to clarify the role of apelin in regulating energy homeostasis in brown adipose tissue (BAT). We examined the central effects of apelin-13 on the brain c-fos like immunoreactivity (c-FLI), BAT temperature and the activity of the sympathetic nerve activity innervating BAT in rats. In the hypothalamus, central infusion into the third cerebral ventricle (i3vt) of apelin-13 caused induction of c-FLI in the paraventricular nucleus (PVN) compared with the controls (PBS-treated) group. In addition, microinjection of apelin-13 into the PVN produced significant increases in BAT temperature. Furthermore, microinjection of apelin-13 treatment increased BAT sympathetic nerve activity compared with controls. We conclude that apelin-13 microinjection into PVN increases sympathetic nerve activity innervating BAT.     

Hypothalamic control of brown adipose tissue in Zucker lean and obese rats. Effect of electrical stimulation of the ventromedial nucleus and other hypothalamic centres

Electrophysiological stimulation of the hypothalamic ventromedial nucleus (VMN) resulted in an increase in interscapular brown adipose tissue (BAT) temperature in both lean and obese (fa/fa) rats. Graded stimulations resulted in progressively larger temperature increases in both lean and obese (fa/fa) groups. Both intraperitoneal injection of propranolol and surgical denervation (but not sham denervation) abolished the increase in BAT temperature following VMN stimulation, in both lean and obese (fa/fa) groups. Electrical stimulation of the supraoptic region, and certain anterior hypothalamic regions also resulted in increases in BAT temperature of lean and obese (fa/fa) rats, but stimulation of the dorsomedial nucleus and regions of the lateral hypothalamus did not affect BAT temperature. All hypothalamic regions capable of activating BAT gave a similar maximum rise in temperature for a given stimulus in lean and obese (fa/fa) rats. These results suggest that the efferent sympathetic pathway from the VMN and other hypothalamic regions of BAT is normal in the obese (fa/fa) rat.     

Corticotropin-releasing factor mRNA and substance P receptor binding in the paraventricular hypothalamic nucleus, central nucleus of the amygdala, and locus coeruleus of sprague-dawley rats following restraint-induced stress

The central mechanism of stress is poorly understood. This study was designed to examine how corticotropin-releasing factor (CRF) neurons, together with substance P (SP) receptors in the paraventricular hypothalamic nucleus (PVN), central nucleus of the amygdala (CeA), and locus coeruleus (LC), are affected by stress. Sprague-Dawley rats were restrained for 2 h. Animals were sacrificed by decapitation immediately after the 2-h restraint (the 0-h group) and 4, 24, or 48 h after restraint. Tissue sections were cut and collected on two sets of slides. Tissue sections of the first set were processed for studying CRF mRNA using ³³P-labeled 60-mer oligonucleotide probe. Immediately adjacent tissue sections were processed for studying SP receptor-binding capacity using ¹²⁵I-SP ligand. Quantitative results showed that CRF mRNAs in the PVN were significantly up-regulated at the 4- and 24-h stages, and they seemed not to be regulated by SP receptors. In addition, SP receptors in the CeA were up-regulated at the 24- and 48-h stages, whereas SP receptors were down-regulated in the LC at the same stages. In concert with the literature indicating SP antagonist’s antidepressive effects, up-regulated SP receptors in the CeA might contribute to the development of stress-related depression. Parts of the results have been presented at the summer neuropeptide conference (June 8–12, 2003, Montauk, NY) as P-37 (Neuropeptides [2003] 37, 192).