title: Neuropeptide Y reverses chronic stress-induced baroreflex hypersensitivity in rats.
abstract: Chronic stress, as a risk factor for cardiovascular diseases, has been reported to result in elevated plasma neuropeptide Y (NPY) and be highly associated with abnormal cardiac autonomic function. This study aimed to explore the effect of NPY on the chronic stress-induced abnormal baroreceptor reflex sensitivity (BRS). Seven types of recognized stressors were used to develop chronic stress rat model. Subcutaneously implanting ALZET mini-osmotic pumps containing NPY were used to evaluate the action of NPY on the stressed male rats. We found that chronic stress showed no influence on baseline systolic blood pressure (SBP) and heart rate (HR), whereas NPY (85 μg for 30 days) could elevate baseline SBP and induce bradycardia in rats intervened by various stimuli. NPY pretreatment could preserve chronic stress-induced decreases in left ventricular systolic pressure (LVSP) and the maximum rate of change in left ventricular pressure in the isovolumic contraction period (+dp/dt(max)) but has shown no effect on left ventricular end diastolic pressure (LVEDP) and the maximum rate of change in left ventricular pressure in the isovolumic relaxation period (-dp/dt(max)). Notably, chronic stress led to baroreflex oversensitivity indicated by the elevated ratio of Δheart rate (HR)/ Δmean arterial blood pressure (MABP) in rats followed by vasoconstrictor (phenylephrine, PE) or vasodilator (sodium nitroprusside, SNP) administration, which was almost completely reversed by NPY pretreatment. The expressions of substance P (SP) and gamma aminobutyric acid A receptor (GABA(A)R) in nucleus tractus solitarius were increased in chronic stress rats, which were counteracted by NPY pretreatment. We conclude that chronic stress-induced baroreflex hypersensitivity could be blocked by NPY pretreatment. Furthermore, the altered expressions of neurotransmitters and receptors in the brainstem might contribute to this process.
authors.affiliation: Department of Pharmacology, Harbin Medical University (the State-Province Key Laboratory of Biomedicine-Pharmaceutics of China), Harbin, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Xie
authors.forename: Lihua
authors.initials: L
authors.lastname: Sun
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Su
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Zhao
authors.forename: Tao
authors.initials: T
authors.lastname: Ban
authors.forename: Huifang
authors.initials: H
authors.lastname: Niu
authors.forename: Jing
authors.initials: J
authors.lastname: Ai
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure; D001835:Body Weight; D001919:Bradycardia / Q000139:chemically induced; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate; D006352:Heart Ventricles / Q000378:metabolism / Q000473:pathology; D009200:Myocardial Contraction; D009478:Neuropeptide Y / Q000008:administration & dosage / Q000494:pharmacology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological; D013373:Substance P / Q000235:genetics / Q000378:metabolism
chemical_list: D009478:Neuropeptide Y; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D009599:Nitroprusside; D010656:Phenylephrine; D013373:Substance P; D015740:Calcitonin Gene-Related Peptide