[Role of rostral ventrolateral medulla in the pressor response to intraventricular (4th) injection of substance P].
Experiments were done in rabbits anaesthetized with urethane and immobilized under artificial respiration. It was found that substance P (SP, 0.8 ng/kg dissolved in 100 microliters 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-Pro2, D-Phe7, D-Trp9]--SP (5-10 ng dissolved in 0.5 microliter CSF) or phentolamine (2-3 micrograms dissolved in 0.5 microliter 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. The results show that SP-induced pulmonary and carotid pressor responses may be mediated through SP-receptor and alpha-adrenergic receptors in the rostral ventro-lateral medulla (rVLM).
Zhang
X H
XH
Department of Physiology, Nanjing Medical University, Nanjing 210029.
Ni
H
H
D000818:Animals; D017704:Baroreflex / Q000187:drug effects; D001794:Blood Pressure; D005260:Female; D007276:Injections, Intraventricular; D008297:Male; D008526:Medulla Oblongata / Q000502:physiology*; D008845:Microinjections; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D018040:Receptors, Neurokinin-1 / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology*
D011942:Receptors, Adrenergic, alpha; D018040:Receptors, Neurokinin-1; D013373:Substance P