Effects of reserpine on the adrenal medulla of the spontaneously hypertensive rat.

1. Reserpine administration resulted in a larger initial decline in adrenal catecholamines in spontaneously hypertensive rats (SHR) than in normotensive Wistar rats (NWR); the difference was eliminated by pretreatment with cholisdondamine. 2. Reserpine also produced a larger increase in SHR catecholamines and dopamine beta-hydroxylase several days later; chlorisondamine pretreatment did not prevent the increases, although it did slightly slow the increases. 3. Vesicles from SHR, or NWR incubated with reserpine in vitro demonstrated equivalent inhibition of adenosine 5'-triphosphate (ATP)-Mg-2+-stimulated adrenaline uptake. 4. Recovery of uptake was more rapid in SHR than in NWR after reserpine inhibition, and this was associated with a burst of new vesicle synthesis in the SHR; chlorisondamine pretreatment reduced the number of new, immature vesicles in reserpine-treated SHR. 5. Both SHR and NWR secreted equal proportions of their adrenal catecholamine contents after nicotine administration. 6. These data suggest that the sympatho-adrenal system of the SHR exhibits an enhanced reflex response to reserpine but that reserpine is equally effective in SHR and NWR in producing blockade of vesicular catecholamine transport; these alterations can affect markedly the actions of autonomic drugs in the SHR.