J Korean Assoc Oral Maxillofac Surg.  2011 Jun;37(3):195-204. 10.5125/jkaoms.2011.37.3.195.

Effects of oropharyngeal taste stimuli in the restoration of the fasting-induced activation of the HPA axis in rats

• Yoo SB
• Lee JH
• Ryu V
• Jahng JW

• KMID: 2189774
• DOI: http://doi.org/10.5125/jkaoms.2011.37.3.195

Abstract

INTRODUCTION
This study examined the regulatory mechanism underlying the meal-induced changes in the hypothalamic-pituitary-adrenal gland (HPA) axis activity.
MATERIALS AND METHODS
Male Sprague-Dawley rats (250-300 g) were hired for two different experiments as follows; 1) rats received either 8% sucrose or 0.2% saccharin ad libitum after 48 h of food deprivation with the gastric fistula closed (real feeding) or opened (sham feeding). 2). rats received 5 ml of intra-oral infusion with 0.2% saccharin or distilled water after 48 h of food deprivation. One hour after food access, all rats were sacrificed by a transcardiac perfusion with 4% paraformaldehyde. The brains were processed for c-Fos immunohistochemistry and the cardiac blood was collected for the plasma corticosterone assay.
RESULTS
Real feedings with sucrose or saccharin and sham feeding saccharin but not sucrose, following food deprivation decreased the plasma corticosterone level. c-Fos expression in the nucleus tractus of solitarius (NTS) of the fasted rats was increased by the consumption of sucrose but not saccharin, regardless of the feeding method. On the other hand, the consumption of sucrose or saccharin with real feeding but not the sham, induced c-Fos expression in the paraventricular nucleus (PVN) of the fasted rats. The intra-oral infusion with saccharin or water decreased the plasma corticosterone level of the fasted rats. Intra-oral water infusion increased c-Fos expression in both the PVN and NTS, but saccharin only in the NTS in the fasted rats.
CONCLUSION
Neither restoration of the fasting-induced elevation of plasma corticosterone nor the activation of neurons in the PVN and NTS after refeeding requires the palatability of food or the post-ingestive satiety and caloric load. In addition, neuronal activation in the hypothalamic PVN may not be an implication in the restoration of the fasting-induced elevation of the plasma corticosterone by oropharyngeal stimuli of palatable food.

Keyword

Hypothalamic-pituitary-adrenal gland axis; Oropharyngeal food stimuli; Paraventricular nucleus; Nucleus tractus Solitarii

MeSH Terms

Animals
Axis, Cervical Vertebra
Brain
Corticosterone
Feeding Methods
Food Deprivation
Formaldehyde
Gastric Fistula
Hand
Humans
Immunohistochemistry
Male
Neurons
Paraventricular Hypothalamic Nucleus
Perfusion
Plasma
Polymers
Rats
Rats, Sprague-Dawley
Saccharin
Salicylamides
Solitary Nucleus
Sucrose
Water
Corticosterone
Formaldehyde
Polymers
Saccharin
Salicylamides
Sucrose
Water