THE POSSIBLE IMPORTANCE OF YOUNG (LARGE) AMINE STORAGE GRANULES FOR ADRENERGIC NERVE TERMINAL FUNCTION

Abstract

This chapter elaborates possible importance of young (large) amine storage granules for adrenergic nerve terminal function. Following one large dose of reserpine, catecholamines and serotonin are depleted centrally and peripherally. The recovery of endogenous noradrenaline (NA) has been studied previously. The reserpine effect is considered to be because of an irreversible blockade of the uptake-storage mechanism of the granules. Because functioning amine granules are necessary for nerve terminal functions 3H-NA uptake-retention and transmission are also markedly depressed during the initial period after reserpine. Onset of recovery of the three different parameters occurs in the rat peripheral tissues 24–36 h after reserpine. Within the same period of time functioning, NA containing granules start to appear in the nerve terminals of long adrenergic neurons. Recovery to normal, however, proceeds differently, 3H-NA uptake-storage and transmission are normalized within 2–3 days, while endogenous NA reach normal levels after 3–5 weeks. These results indicate (1) that uptake-retention of 3H-NA occurs mainly in “young” amine granules recently arrived to the nerve terminals, and (2) that this capacity of the “young” granules is rather shortlasting. The T½ for this capacity has been estimated to around 12 h.