Published Online
on March 31, 2003

A more recent version of this article appeared on May 1, 2003

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Submitted on October 24, 2002
Revised on November 19, 2002

Hypotension and Reduced Catecholamines in Neuropeptide Y Transgenic Rats

Mieczyslaw Michalkiewicz^*; Kriss M. Knestaut; Elena Yu. Bytchkova; and Teresa Michalkiewicz

From the Department of Physiology, Medical College of Wisconsin, Milwaukee.

^* To whom correspondence should be addressed. E-mail: mmichalk{at}mcw.edu.

Abstract--The neurons that control blood pressure express neuropeptide Y. Administered centrally, this neuropeptide reduces blood pressure and anxiety, together with lowering sympathetic outflow. The generation of neuropeptide Y transgenic rats overexpressing this peptide, under its natural promoter, has allowed us to examine the role of endogenous neuropeptide Y in the long-term control of blood pressure by the sympathetic nervous system. This study tested a hypothesis that endogenous neuropeptide Y acts to reduce blood pressure and catecholamine release. Blood pressure was measured by radiotelemetry in conscious male transgenic and nontransgenic littermates (control). Novel cage with cold water and forced swimming were used as stressors. Catecholamines were determined in 24-hour urine (baseline) and plasma (cold water stress) by a radioenzymatic assay. Blood pressures in baseline and during the stresses were significantly reduced in the transgenic rats. The lower blood pressure was associated with reduced catecholamines, lower decrease in pressure after autonomic ganglionic blockade, and increased longevity. Data obtained through the use of this transgenic rat model support and extend the evidence for the previously postulated sympatholytic and hypotensive effects of neuropeptide Y and provide novel evidence for an important physiological role of endogenous peptide in blood pressure regulation. As indicated by the increased longevity of these rats, in long-term regulation, these buffering actions of neuropeptide Y may have important cardiovascular protective effects against sympathetic hyperexcitation.

Key words: hypotension • nervous system, sympathetic renal • stress • sympatholytics • catecholamines • rats, transgenic

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