The daily pattern of Fos synthesis by hypothalamic pro-opiomelanocortin neurons is unaffected by adrenalectomy in the rat.
At the onset of dark, a large population of rat mediobasal hypothalamic (MBH) pro-opiomelanocortin (POMC) neurons starts spontaneously expressing Fos-immunoreactivity (Fos-IR). Here we studied the effect of adrenalectomy upon this expression since circulating corticosteroids, which increase in the rat with the onset of behavioural wakening, are thought to modulate the basal expression of MBH POMC mRNA. Hence, groups of intact, adrenalectomised and sham-operated rats were sacrificed at times when Fos synthesis by POMC neurons is known to show either nadir (at light-offset) or peak (6 h after light-offset) values. Brains were processed for Fos- and/or POMC immunohistochemistry. This allowed us to show that, in all experimental groups, Fos-IR is hardly expressed in MBH POMC neurons at the onset of dark, whereas it is strongly induced 6 h later. We concluded that such an induction is not triggered through the known evening rise of plasma corticosteroid levels.
Jamali
K A
KA
Laboratoire de Neurocytochimie Fonctionnelle, Université de Bordeaux I, CNRS URA 339, Talence, France.
Corio
M
M
Dubourg
P
P
Thenailler
C
C
Tramu
G
G
D000315:Adrenalectomy / Q000009:adverse effects*; D000818:Animals; D007031:Hypothalamus / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D007150:Immunohistochemistry; D009474:Neurons / Q000737:chemistry / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar
D016760:Proto-Oncogene Proteins c-fos; D011333:Pro-Opiomelanocortin