Cardiovascular effects of dynorphin A-(1-8), dynorphin A-(1-13) and dynorphin A-(1-17) microinjected into the preoptic medialis nucleus of the rat

Multiple forms of Dynorphin A (Dyn A) are present in cardiovascular nuclei in the hypothalamus, along with kappa-opiate receptors. To study the potential role of Dyn A in cardiovascular regulation, various Dyn A species [Dyn A-(1-8; 1-13; 1-17)] were microinjected into the preoptic nucleus (POM) of the anesthetized rat. Dyn A-(1-17) was tenfold more potent than Dyn A-(1-13), and over 100-fold more potent than Dyn A-(1-8) in reducing systemic blood pressure. High doses of Dyn A-(1-17) (6 nmoles) produced shock with severe bradycardia and bradypnea. These data suggest that Dyn A may be an endogenous modulator of cardiorespiratory variables in the anteroventral hypothalamus, and demonstrate that the larger fragments of the peptide are more active in eliciting central cardiorespiratory activity in this region.