Segura-Chama P, Rivera-Cerecedo CV, González-Ramírez R, Felix R, Hernández-Guijo JM, Hernández-Cruz A. Wistar-Kyoto; spontaneously hypertensive rats; Ca 2ϩ channel splice variants THE SPONTANEOUSLY HYPERTENSIVE rat (SHR) is an inbreed of the Wistar strain widely used as a model to investigate the mechanisms underlying essential hypertension (31). The normotensive descendants of Wistar rats that National Institutes of Health investigators obtained in 1971 from the colony in Kyoto (WKY) from which the SHR strain was originally derived, are often used as controls for the SHR (16). Nonetheless, it has been argued that this strain is unsuitable as control studies because of genetic heterogeneity and the high incidence of spontaneous hypertension (20). Our laboratory recently compared the electrophysiological properties of voltage-gated Ca 2ϩ currents (I Ca ) in adrenal chromaffin cells (CCs) from WKY rats and SHR to determine whether the catecholamine hypersecretion reported in CCs from the SHR strain (27, 28) was due to an augmented function of voltage-gated Ca 2ϩ channels. Our results showed that the electrophysiological and pharmacological properties of I Ca in adrenal CCs from SHR and WKY are indistinguishable (39), implying that catecholamine hypersecretion in SHR CCs cannot be attributed to augmented Ca 2ϩ entry, and also that the choice of the WKY strain as control was appropriate in this case. Nonetheless, we noticed differences in the kinetics and voltage dependence of