延髓腹外侧区微量注射L-NAME对内脏-减压反应的影响

Effect of L-NAME microinjection into ventrolateral medulla on viscero-depressor response

目的观察延髓腹外侧区头端(RVLM)和尾端(CVLM)微量注射N-硝基-L-精氨酸甲酯(L-NAME)对内脏-减压反应的影响,探讨静注L-NAME使该反应产生翻转的中枢机制。方法用电刺激内脏大神经传入纤维的方法模拟内脏痛,比较RVLM和CVLM微量注射L-NAME前后刺激神经时血压的变化情况。结果RVLM给药后基础血压升高(P<0.01);给药前刺激神经时为降压反应,△MBP=-(26.19±6.77)mmHg(1mmHg=0.133kPa),而给药后刺激时血压下降的效应被抵消,△MBP=-(15.56±6.63)mmHg(P<0.01)。CVLM给药后基础血压降低(P<0.01),给药前刺激神经时为降压反应,△MBP=-(28.78±11.71)mmHg,而给药后刺激时血压仍下降,但△MBP=-(16.63±9.30)mmHg(P<0.01)。若提前注入L-Arg,可以取消L-NAME的作用,即基础血压和刺激后的反应性血压的变化均恢复到原来的水平。结论RVLM和CVLM微量注射L-NAME可部分抵消内脏-减压反应,提前注入L-精氨酸(L-Arg)可以取消L-NAME的上述作用。表明VLM参与了内脏-减压反应并通过中枢NO通路起作用;静注L-NAME引起的翻转作用则是由于抑制了内源性NO的生成。

AIM To study the effect of microinjection of L-NAME into rostral ventrolateral medulla （RVLM） or caudal ventrolateral medulla （CVLM） on the viscero-depressor response and to probe into the central mechanism of the reversion of the response induced by intravenous injection of L-NAME. METHODS Visceral pain was imitated by electric stimulation of the greater-splanchnoafferents. The basal blood pressure （BP） and the pressure responses to the electric stimulation were observed before or after the microinjection of L-NAME into RVLM and CVLM. RESULTS The basal BP increased after the microinjection into RVLM （P 〈 0.01 ）. When the nerve was stimulated without the microinjection of L-NAME into RVLM, BP decreased by - （26.19 ± 6.77 ）mmHg, while the responsive BP decreased by - （ 15.56 ± 6.63 ） mmHg following the microinjection of L-NAME （ P 〈 0.01 ）. After the L-NAME microinjection into CVLM, the basal BP decreased （ P 〈 0.01 ）. When the nerve was stimulated without the microinjection of L-NAME into CVLM, BP decreased by - （28.78 ± 11.71 ）mmHg, while the response of BP was reduced partly to - （ 16.63 ± 9.30） mmHg after microinjection of L-NAME （P 〈0.01 ）. If L-argentine was microinjected before L-NAME microinjection, both the basal BP and the responsive BP were unchanged. CONCLUSION the viscero-depressor response. VLM Microinjection of L-NAME into RVLM or CVLM can partly reduce is involved in the viscero-depressor response and exerts its effect through the central NO pathway. Intravenous injection of L-NAME reverses the response possibly by inhibiting the intrinsic nitric oxide synthesis.