关于儿茶酚胺对心肌的正性变力作用机制，正确的描述是

试卷相关题目

SQL Error: select id,body,options from ***_enewstiku where sourceid='28371' and id < 2320112 and id<>'2320112' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='28371' and id > 2320112 and id<>'2320112' order by id asc limit 5