Itoh H, Buñag R D
Department of Pharmacology, College of Health Sciences and Hospital, University of Kansas Medical Center, Kansas City 66103.
Mech Ageing Dev. 1992 Jun;64(1-2):69-84. doi: 10.1016/0047-6374(92)90097-w.
To explore whether catecholaminergic lesions produced chemically in the nucleus tractus solitarius (NTS) would alter the baroreflex impairment that normally occurs with age, we compared baroreflex responses in 3- and 14-month-old rats given bilateral microinjections of 6-hydroxydopamine (6-OHDA) or its vehicle into the NTS. After 2 weeks, basal pressures were unaffected but heart rates were lower in 14- than in 3-month-old rats. Sympathetic nerve inhibition elicited reflexly during intravenous infusions of sodium nitroprusside was reduced in 3-month-old rats, but increased in 14-month-old rats. Depressor, bradycardiac, and sympatho-inhibitory responses to afferent aortic nerve stimulation were likewise reduced in 3-month-old rats and oppositely enhanced in 14-month-old rats. Enhanced bradycardia probably does not depend on increased parasympathetic sensitivity because responses to vagal stimulation did not differ between age groups. Although underlying mechanisms remain uncertain, by showing that baroreflex responses become altered differently in 3- and 14-month-old rats by 6-OHDA these results suggest that the baroreflex changes normally occurring with age may be due, at least in part, to modified catecholaminergic mechanisms in the NTS.
为探究孤束核（NTS）中化学诱导产生的儿茶酚胺能损伤是否会改变正常情况下随年龄增长出现的压力反射损害，我们比较了3月龄和14月龄大鼠双侧向NTS微量注射6-羟基多巴胺（6-OHDA）或其溶媒后的压力反射反应。2周后，基础血压未受影响，但14月龄大鼠的心率低于3月龄大鼠。静脉输注硝普钠期间反射性诱发的交感神经抑制在3月龄大鼠中减弱，而在14月龄大鼠中增强。对主动脉传入神经刺激的降压、心动过缓和交感抑制反应在3月龄大鼠中同样减弱，而在14月龄大鼠中则相反增强。心动过缓增强可能不依赖于副交感神经敏感性增加，因为不同年龄组对迷走神经刺激的反应没有差异。尽管潜在机制尚不确定，但通过显示6-OHDA使3月龄和14月龄大鼠的压力反射反应发生不同改变，这些结果表明正常情况下随年龄增长出现的压力反射变化可能至少部分归因于NTS中儿茶酚胺能机制的改变。
