Effect Of Microinjection Of L-NAME Into Ventrolateral Medulla On Viscero-depressor Response

Objective: To observe the effect of intravenous injectionand microinjection into ventrolateral medulla (including rostraland caudal) of L-NAME on the viscero-depressor response andto probe into the central mechanism of the reversion of theresponse induced by the intravenous injection of L-NAME. Tryto discover the mechanism of the shock induced by visceral pain,thereby, to ford reference for prevention and cure in clinic to theconcomitant symptom coursed by viscero-depressor response Methods: The visceral pain was imitated by electricstimulation of the greater-splanchnoafferents and a model ofviscero-depressor response was established on rats. Divided 96male adult Sprague-Dawley rats into 3 groups: ①intravenousinjection group, ② RVLM (rostral ventrolateral medulla)microinjection group,③CVLM (caudal ventrolateral medulla)microinjection group. The blood pressure (BP), pulse pressure(PP), heart rate(HR) and their responses to the electricstimulation were observed before or after intravenous injectionand microinjection of L-NAME into RVLM and CVLM. Results: When the greater–splanchnoafferents was stimu-lated in the basal state, BP was decreased, the pulse pressurebecame smaller and the heart rate became slower. Result of the 4英 文 摘 要experiment after drug injection as follows: 1．Confront to thecomparing experiment in the same group, the basal BP and theresponsive BP were both changed after injection of L-NAME.Intravenous injection group: The basal BP was increased from90.99±7.94mmHg to 100.51±8.60mmHg after intravenousinjection of L-NAME (15mg/kg,0.5ml) (P﹤0.005).Stimulationafter a 15min interval caused an increasing response of BP(P﹤0.01), as well as the pulse pressure became greater and the heartrate became faster (P <0.005,P <0.005). RVLM microinjectiongroup : The basal BP was increased from 90.11±6.47 mmHg to106.58±9.31mmHg after microinjection of L-NAME(240ug/ul,0.1ul) into RVLM (P﹤0.005). When the nerve was stimulatedafter 15 min, BP was also decreased, but the decreasing extentwas obviously reduced (P﹤0.005). Before microinjection, theextent was -26.19±6.77mmHg while it is -15.56±6.63mmHgafter injection of L-NAME, meanwhile, the decreasing extent ofthe pulse pressure and the heart rate were obviously reduced,too(P <0.01 both). CVLM microinjection group: The basal BPwas decreased from 100.11±15.11mmHg to 74.43±9.06mmHg(P﹤0.01) after microinjection of L-NAME(240ug/ul, 0.1ul)into CVLM. 15min later, stimulation of the nerve also caused adecrease of BP with an obviously reductive extent compared tothe decrease before the microinjection in the same rat(P﹤0.005).At the same time, the decreasing extent of the pulse pressureand the heart rate were obviously reduced, too (P <0.01 both). 2.Confront to the comparing experiment in the same group, the 5英 文 摘 要responsive BP was changed after injection of L-arginine+L-NAME. Intravenous injection group: The BP decreasedslightly after intravenous injection of L-arginine (400mg/kg,0.5ml), and recovered to the basal standard soon. 5 min later, BPwas still increased after the injection of L-NAME(15mg/kg,0.5ml) by a not distinct statistic level(P >0.05). After the secondinjection for 15min, the nerve was stimulated again and therewas an induced BP reaction in every case by a similar extent tothe reaction before injection(before injection△MBP=-12.17±2.95mmHg, after injection△ MBP=-11.69±2.18mmHg, P>0.05).Meanwhile, the reaction of pulse pressure and heart ratewere recovered to the basal standard, too(P>0.05). RVLMmicroinjection group: BP was decreased from 93.26±9.55mmHg to72.46±14.18mmHg (P <0.01)after microinjection ofL-arginine(186ug/ul,0.1ul) into RVLM. Following microinjec-tion of L-NAME(240ug/ul, 0.1ul) into RVLM 5min later, theresponse of BP was increased a little, but did not reach thedistinct statistic level(P﹥0.05). Upon st...