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Role of rostral ventrolateral medulla in the pressor response to intraventricular (4th) injection of substance P

Zhang Xiaohui, Ni Hui

Department of Physiology，Nanjing Medical University. Nanjing 210029,China

Abstract

Experiments were done in rabbits anaesthetized with urethane and immobilized under artificial respiration. It was found that substance P (SP, 0.8ng/kg dissolved in 100 #mu#l artificial cerebro-spinal fluid, CSF) injected into the 4th ventricle induced either a rise or a drop of pulmonary arterial pressure (PAP) with predominated pressor response. In addition, a rise in carotid arterial pressure (CAP) and reduction in heart rate (HR) were also observed, whereas no significant alteration in PAP, CAP and HR was observed. Microinjection of SP receptor antagonist [D-Pro~(2), D-Phe~(7), D-Trp~(9)] -SP (5-10 ng dissolved in 0.5 #mu#l CSF) or phentolamine (2-3 #mu#g dissolved in 0.5#mu#l CSF) into the bilateral rostral ventrolateral medulla (rVLM) prior to intraventricular injection of SP could block the SP-induced pressor responses in pulmonary and carotid arteries, while microinjection of SP receptor antagonist or phentolamine into bilateral caudal ventrolateral medulla (cVLM) at the same dosage had no effect.

Key words: Substance P;Pulmonary arterial pressure;Carotid arterial presrure;Pressor response rostral ventrolateral medulla;#alpha#-adrenergic receptor;

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Citing This Article：

Zhang Xiaohui, Ni Hui. Role of rostral ventrolateral medulla in the pressor response to intraventricular (4th) injection of substance P. Acta Physiol Sin 1998; 50 (2): (in Chinese with English abstract).