This study was designed to evaluate if a long-term dietary ALA intake supplied as whole grain extruded linseed can increase the endogenous production of n-3 LC-PUFAs in healthy adult rats, influence heart rate (HR) and adrenergic response like DHA-rich diets do. The DHA enrichment was evaluated using fatty acid analysis of tissue phospholipids after 8, 16, 24 and 32 weeks of feeding in male Wistar rats randomly assigned to 3 dietary groups (n=8 in each group/ period) fed a reference fat (RFD) or ALA-rich diet (ALA) or DHA-rich diet (DHA). A week before sacrifice, under anaesthesia, HR was measured from ECG recordings during an adrenergic stimulation challenge (n=8). Dietary ALA produced a significant increase of DHA in cardiac membranes as compared to RFD-fed rats. The DHA content in cardiac membrane was close to 10% with ALA rich diet vs 20% with the DHA rich diet and 4% with the RFD diet. The cardiac fatty acid-profile was established after 2 months and remained mainly unchanged after. Whatever the diet, DHA in heart decreased with age. Nevertheless it remained over 15% with pure DHA and heart from older ALA-fed rats remained richer in DHA than those from younger RFD fed rats. Basal HR decreased with ALA (395±24.9 bpm) intermediate between those of DHA (375±26.4 bpm) and RFD (407±36.7 bpm). Both n-3 dietary intakes contribute to enhance the chronotropic response to adrenergic agonist stimulation. The regulation of HR by nuro-humoral mediators may be controlled by lower content of DHA, such as those brought by a dietary supply of extruded linseed (ALA).