Korean J Physiol Pharmacol.  2012 Oct;16(5):333-337. 10.4196/kjpp.2012.16.5.333.

cAMP/PKA Agonist Restores the Fasting-Induced Down-Regulation of nNOS Expression in the Paraventricular Nucleus

• Yoo SB
• Lee S
• Lee JY
• Kim BT
• Lee JH
• Jahng JW

• KMID: 1493966
• DOI: http://doi.org/10.4196/kjpp.2012.16.5.333

Abstract

Gene expression of neuronal nitric oxide synthase (nNOS) changes in the hypothalamic paraventricular nucleus (PVN) depending on feeding conditions, which is decreased during food deprivation and restored by refeeding, and phosphorylated cAMP response element binding protein (pCREB) was suggested to play a role in its regulation. This study was conducted to examine if the fasting-induced down-regulation of the PVN-nNOS expression is restored by activation of cAMP-dependent protein kinase A (cAMP/PKA) pathway. Freely moving rats received intracerebroventricular (icv) injection of cAMP/PKA activator Sp-cAMP (40 nmol) or vehicle (sterilized saline) following 48 h of food deprivation. One hour after drug injections, rats were transcardially perfused with 4% paraformaldehyde, and the PVN tissues were processed for nNOS or pCREB immunohistochemistry. Sp-cAMP significantly increased not only nNOS but also pCREB immunoreactivities in the PVN of food deprived rats. Fasting-induced down-regulation of the PVN-nNOS was restored by 1 h after the icv Sp-cAMP. Results suggest that cAMP/PKA pathway may mediate the regulation of the PVN-nNOS expression depending on different feeding conditions.

Keyword

Food deprivation; Gene expression; Neuronal nitric oxide synthase; Paraventricular nucleus; Rat

MeSH Terms

Animals
Cyclic AMP Response Element-Binding Protein
Cyclic AMP-Dependent Protein Kinases
Down-Regulation
Food Deprivation
Formaldehyde
Gene Expression
Immunohistochemistry
Nitric Oxide Synthase Type I
Paraventricular Hypothalamic Nucleus
Polymers
Rats
Cyclic AMP Response Element-Binding Protein
Cyclic AMP-Dependent Protein Kinases
Formaldehyde
Nitric Oxide Synthase Type I
Polymers

Figure

• 

  Fig. 1 nNOS immunoreactivity and number of nNOS-ir neurons in the parvocellular and the magnocellular PVN. Rats were sacrificed for nNOS immunohistochemistry at 1 h after an intracerebroventricular (icv) injection of Sp-cAMP or saline vehicle. FC/veh, free-fed control rats received icv administration of 5 µl sterilized saline; FD/veh, 48 h food deprivation and received icv administration of 5 µl sterilized saline; FD/Sp-cAMP, 48 h food deprivation and received icv administration of 5 µl of 40 nmol Sp-cAMP in sterilized saline; FD/Rp-cAMP, 48 h food deprivation and received icv administration of 5 µl of 40 nmol Rp-cAMP in sterilized saline; mP, medial parvocellular subdivision; pM, posterior magnocellular subdivision; PVN, paraventricular nucleus; 3v, third ventricle; *p<0.05, **p<0.01 vs. FC/veh; #p<0.05 vs. FD/veh, Values are presented as means±S.E.

• 

  Fig. 2 pCREB immunoreactivity and number of pCREB-ir nuclei in the parvocellular and the magnocellular PVN. Rats were food deprived for 48 h and then received icv administration of 5 µl sterilized saline (vehicle) or 40 nmol Sp-cAMP in sterilized saline, and sacrificed 1 h after the icv injections for pCREB immunohistochemistry. mP, medial parvocellular subdivision; pM, posterior magnocellular subdivision; PVN, paraventricular nucleus; 3v, third ventricle; *p<0.05 vs. vehicle controls; Values are presented as means±S.E.

• 

  Fig. 3 Plasma corticosterone levels at 1 h after an icv administration of Sp-cAMP or saline vehicle. FC/veh, free-fed control rats received icv administration of 5 µl sterilized saline; FD/veh, 48 h food deprivation and received icv administration of 5 µl sterilized saline; FD/Sp-cAMP, 48 h food deprivation and received icv administration of 5 µl of 40 nmol Sp-cAMP in sterilized saline; *p<0.05 vs. FC/veh, Values are presented as means±S.E.

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