ABSTRACT
OBJECTIVE: To determine the cardiovascular actions of salusin-α in the caudal ventrolateral medulla (CVLM) in anesthetized rats. METHODS: Sixty-one anesthetic male SD rats were employed in the present study. The dose-dependant effects of salusin-α (0.04-4 pmol) on blood pressure and heart rate in the CVLM were determined by unilateral microinjection of salusin-α or artificial cerebrospinal fluid (aCSF) into the CVLM in 25 rats. In the other 36 rats, a CSF, kynurenic acid (Kyn), atropine, hexametho-nium (Hex) in the CVLM or a CSF/muscimol in the RVLM were given in advance to determine the mechanism of the cardiovascular actions of intra-CVLM salusin-α. RESULTS: Unilateral microinjection of salusin-a into the CVLM produced a dose-dependent hypotension and bradycardia. Prior administration of Kyn (1 nmol) or Hex (120 pmol) into the CVLM did not alter the hypotension and bradycardia induced by intra-CVLM salusin-α (P>0.05). But prior administration of atropine into the CVLM or pretreatment with muscimol within RVLM almost completely abolished the hypotension and bradycardia evoked by intra-CVLM salusin-α (P<0.05). CONCLUSION: Microinjection of salusin-α into the CVLM produces significantly hypotension and bradycardia, which probably originates from suppressing the activities of presympathetic neurons in the RVLM.
ABSTRACT
Objective:To investigate the mechanism of the reversal effect of acupuncture on the fall of blood pressure induced by angiotensin-(1-7)[Ang-(1-7)] in the caudal ventrolateral medulla(CVLM) of rats. Methods: Ang-(1-7) and its selective receptor antagonist (D-Ala7), Ang-(1-7) and Ang-(779) were microinjected into the CVLM respectively to induce the change of blood pressure, during which, the concentrations of amino acid neurotransmitters were detected by means of microdialysis and high performance liquid chromatography(HPLC)combined with fluorescent detector, on the other hand, the effects of electro-acupuncture (EA) on the level of blood pressure and the concentrations of amino acid neurotransmitters were also observed. Results:Unilateral microinjection of Ang-(1-7) into the CVLM could decrease the blood pressure (BP), which was accompanied by an increase in the release of Glu and a decrease in the release of Tau in the same site; Whereas microinjection of Ang-779 into the CVLM could elevate BP, which was accompanied by a decrease in the release of Glu and an increase in the release of Tau; EA at acupoint Zusanli (ST 36) for 20 min could inhibit the fall of blood pressure induced by microinjection of Ang-(1-7) into the CVLM and the elevation of blood pressure induced by microinjection of Ang-779 into the CVLM, and in the meantime, it could inhibit the changes of the release of Glu and Tau induced by microinjection of Ang-(1-7) and Ang-779 into the CVLM. Conclusion: The reversal effect of EA on the fall or elevation of blood pressure induced by microinjection of Ang-(1-7) or Ang-779 into the CVLM might be related to the changes of Glu and Tau release.
ABSTRACT
Objective:To explore the roles of the caudal ventrolateral medulla(CVLM) in the central anti-hypertensive mechanism. Methods : In 20 urethane-anesthetized SD rats, the effects of I1-imidazoline receptor and ?2-adrenceptor antagonists (microinjection into the CVLM) on the cardiovascular responses induced by intravenous clonidine were observed. Results: Prior bilateral microinjection of mixed antagonist idazoxan (I1-imidazoline receptor and a2-adrenceptor) into the CVLM not only decreased the mean arterial pressure [(-17. 3 ? 6. 9) mmHg, 1 mmHg = 0. 133 kPa, P
ABSTRACT
After injecting retrograde tracer fiuoro-gold (FG) into the parabrachial region(PB), caudal ventrolateral medulla(CVLM) and the fourth segment of cervical spinal cord (C4), respectively, neurons in laminae I ～ Ⅱ of the medullary dorsalhorn projecting to the above mentioned brain areas were observed. PB received projections from bilateral laminae I and Ⅱ withan ipsilateral dominance; CVLM and C4 received projections from ipsilateral laminae I and Ⅱ. Neurons projecting to C4 werevery sparsely distributed in laminae I and Ⅱ of the medullary dorsal horn. The projecting neurons in outer part of lamina Ⅱwere more than those in inner part of lamina Ⅱ . Combined with immunofluorescence histochemistry for calbindin-D28k(CB) andparvalbumin(PV), it was demonstrated that a part of neurons projecting to PB or CVLM showed CB-like immunoreactivity, butnone of them exhibited PV-like immunoreactivity. There were only a few neurons in lamina Ⅱ projecting to C4 and they exhibitedneither CB- nor PV-like immunoreactivity. The present study provides further evidence for the existence of projecting neurons inlamina Ⅱ and suggests that immunostaining against CB and PV may distinguish two neuronal subpopulations in lamina Ⅱ .