Immobilization induced fos expression in the medial and lateral hypothalamic areas: a limited response of hypocretin neurons.
Induction of Fos, a proto-oncogene c-fos protein product, was immunohistochemically examined in the rat hypothalamic neurons 3 h after a single (1 x120 min) or repeated (7x 120 min) immobilization (IMO) stress. The aim of the present study was to reveal a possible parallelism in the cell activation between the medial and lateral hypothalamic neurons, especially between the stress responsive neurons in the hypothalamic paraventricular nucleus (PVN) and hypocretin (Hcrt) synthesizing neurons, i.e. suspected stress active neurons of the lateral hypothalamus. After IMO, the animals were perfused and their brains processed with immunohistochemistry for Fos or Fos/Hcrt proteins. Acute IMO elicited extensive Fos expression in both the examined areas. Excessive Fos expression was mainly seen in the PVN, while Hcrt neurons failed to show a broad response (appr. 5%) to single IMO. Clear occurrence of Fos signal was also seen in both hypothalamic areas of IMO-habituated rats. However, in these animals, in both areas examined, the number of Fos neurons was considerably suppressed, including the PVN. These results indicate that IMO is able to evoke a concurrent activation of Fos in many medial and lateral hypothalamic neurons. However, the scanty response of Hcrt neurons to acute IMO does not allow to assort them to a distinct IMO stress-responsive neuronal phenotypes of the brain.
Kiss
Alexander
A
Laboratory of Functional Neuromorphology, Institute of Experimental Endocrinology, Slovak Academy of Sciences, Vlarska str. 3, 833 06 Bratislava, Slovakia. ueenkiss@savba.sk
D000818:Animals; D007026:Hypothalamic Area, Lateral / Q000378:metabolism; D007031:Hypothalamus / Q000378:metabolism*; D007033:Hypothalamus, Middle / Q000378:metabolism; D007103:Immobilization; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism*; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D018377:Neurotransmitter Agents / Q000378:metabolism; D000068797:Orexins; D010286:Paraventricular Hypothalamic Nucleus / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013315:Stress, Psychological / Q000378:metabolism*
D047908:Intracellular Signaling Peptides and Proteins; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D000068797:Orexins; D016760:Proto-Oncogene Proteins c-fos