Increase in norepinephrine but not nitric oxide metabolite levels in the hypothalamic paraventricular nucleus region in response to air jet and swing rotation in freely moving conscious rats.

ABSTRACT

Chronically instrumented, conscious rats were used to examine whether mild exteroceptive stress produces differential neurochemical changes in the hypothalamic paraventricular nucleus (PVN) region. We constructed systems for stress experiment of air jet and swing rotation that were conducted on freely moving conscious rats in a computer-controlled home cage. Concentration of extracellular norepinephrine (NE) and nitric oxide metabolites (NO(X)(-)), nitrite (NO(2)(-)) and nitrate (NO(3)(-)), in the PVN region was then measured by high-performance liquid chromatography with the respective detector; blood pressure (BP) and heart rate (HR) were also measured. Both stressors increased NE concentration in the PVN region as well as BP and HR. Neither stressor altered NO(X)(-) in the PVN region. Cardiovascular and NE changes showed reproducibility in intensity-dependent manner in response to repeated stressors. This finding demonstrated that exteroceptive stress produced different effects on the neurochemical mediators, NE and NO, in the PVN region.