We examined α1A-adrenergic receptor (AR) mediation of preconditioning in a novel α1A-AR cardiac transgenic (TG) rat model (α1A-TG). Compared with nontransgenic littermates (NTLs), in conscious α1A-TG rats, heart rate was reduced, contractility [left ventricle (LV) +dP/d t, ejection fraction, end-systolic elastance] was significantly enhanced, and triple product (LV systolic wall stress × LV +dP/d t × heart rate) was unchanged. However, infarct size (IS)/area at risk (AAR) in response to ischemia-reperfusion (30 min coronary occlusion/3 h reperfusion) was reduced to 35 ± 4.6% in α1A-TGs vs. 52 ± 2.2% in NTLs ( P < 0.05). Second window preconditioning reduced IS/AAR in NTLs to 29 ± 2.7% but did not afford further protection in α1A-TGs. In contrast, with first window preconditioning, IS/AAR was reduced to similar levels in both α1A-TGs (12 ± 1.4%) and NTLs (10 ± 1.1%). In untreated α1A-TGs, cardioprotection was associated with enhanced myocardial phosphorylated (p)-mitogen/extracellular signal-regulated kinase (MEK), p-extracellular signal-regulated kinase (ERK), and inducible nitric oxide synthase (iNOS) at the protein level, along with a 1.3-fold increase in total nitric oxide synthase activity like in second window preconditioning. Affymetrix microarrays revealed that few genes (4.6% of 3,172 upregulated; 8.8% of 3,498 downregulated) showed directionally similar changes in α1A-TGs vs. NTLs subjected to second window preconditioning. Thus, second, but not first, window cardioprotection is evident in α1A-TGs in the absence of ischemic preconditioning and is mediated by iNOS activation associated with MEK/ERK phosphorylation. Transcriptionally, however, second window preconditioning is considerably more complex than α1A-TG preconditioning, with the alteration of thousands of additional genes affording no further protection than that already available in α1A-TG rats.