Activation of anorexigenic pro-opiomelanocortin neurones during refeeding is independent of vagal and brainstem inputs.
After fasting, satiety is observed within 2 h after reintroducing food, accompanied by activation of anorexigenic, pro-opiomelanocortin (POMC)-synthesising neurones in the arcuate nucleus (ARC), indicative of the critical role that α-melanocyte-stimulating hormone has in the regulation of meal size during refeeding. To determine whether refeeding-induced activation of POMC neurones in the arcuate is dependent upon the vagus nerve and/or ascending brainstem pathways, bilateral subdiaphragmatic vagotomy or transection of the afferent brainstem input to one side of the ARC was performed. One day after vagotomy or 2 weeks after brain surgery, animals were fasted and then refed for 2 h. Sections containing the ARC from vagotomised animals or animals with effective transection were immunostained for c-Fos and POMC to detect refeeding-induced activation of POMC neurones. Quantitative analyses of double-labelled preparations demonstrated that sham-operated and vagotomised animals markedly increased the number of c-Fos-immunoreactive (-IR) POMC neurones with refeeding. Furthermore, transection of the ascending brainstem pathway had no effect on diminishing c-Fos-immunoreactivity in POMC neurones on either side of the ARC, although it did diminish activation in a separate, subpopulation of neurones in the dorsomedial posterior ARC (dmpARC) on the transected side. We conclude that inputs mediated via the vagus nerve and/or arising from the brainstem do not have a primary role in refeeding-induced activation of POMC neurones in the ARC, and propose that these neurones may be activated solely by direct effects of circulating hormones/metabolites during refeeding. Activation of the dmpARC by refeeding indicates a previously unrecognised role for these neurones in appetite regulation in the rat.
Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary. fekete.csaba@koki.mta.hu
C
C
Fekete
G
G
Zséli
P S
PS
Singru
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A
Kádár
G
G
Wittmann
T
T
Füzesi
W
W
El-Bermani
R M
RM
Lechan
D000818:Animals; D000855:Anorexia / Q000378:metabolism; D001067:Appetite Depressants / Q000378:metabolism; D001069:Appetite Regulation / Q000502:physiology; D001111:Arcuate Nucleus of Hypothalamus / Q000378:metabolism / Q000502:physiology; D001933:Brain Stem / Q000378:metabolism / Q000502:physiology*; D004326:Drinking / Q000502:physiology; D004435:Eating / Q000502:physiology*; D005215:Fasting; D008297:Male; D009474:Neurons / Q000378:metabolism* / Q000502:physiology*; D011333:Pro-Opiomelanocortin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D009435:Synaptic Transmission / Q000502:physiology; D014630:Vagus Nerve / Q000378:metabolism / Q000502:physiology*
D001067:Appetite Depressants; D011333:Pro-Opiomelanocortin