Effect of age on cardiac norepinephrine release in the female rat

We previously demonstrated an age-related decline in K(+)-induced norepinephrine (NE) release from cardiac synaptosomes prepared from 6- and 24-month-old male F344 rats. The purpose of the present study was to determine if the age-related decrease in NE release seen in male F344 rats is also present in female F344 rats. K(+)-induced NE release was assessed in cardiac synaptosomes prepared from 6-, 12-, 18-, and 24-month-old male and female F344 rats. NE release was significantly greater in young male rats, compared to old male rats. However, no age-related decrease in NE release was observed in the female rats. In contrast to previous observations in male rats, raising extracellular [Mg2+], an inorganic Ca2+ channel blocker, reduced NE release to the same extent in all female ages. Omega-conotoxin, an organic Ca2+ channel blocker, also decreased NE release to the same extent in all female ages. These studies suggest that in contrast to aging male rats, cardiac adrenergic nerve terminals of aging female rats maintain their capacity to release NE.