Relationship between accumulation, storage and overflow of noradrenaline in the rat salivary gland after chronic treatment with guanethidine.

1 The effect of guanethidine on the endogenous noradrenaline (NA) content, accumulation and overflow of [3H]-noradrenaline ([3H]-NA) in the rat salivary gland was examined at various times after drug administration. 2 Twenty-four h after a single injection of guanethidine (1 or 10 mg/kg s.c.), the respective values for the endogenous NA content and for the accumulation and overflow of [3H]-NA were approximately 55, 85, 30%, and 15, 55, 10% of the controls. 3 Although [3H]-NA accumulation had returned to control levels within 48 h after the dose of 10 mg/kg guanethidine, the overflow of [3H]-NA evoked by electrical stimulation or excess potassium (K+) remained depressed. 4 After the low or the high dose of guanethidine, the NA content of the salivary gland was restored to about 50% of the normal value between 4 to 24 and 48 to 72 h, respectively. 5 The accumulation of [3H]-NA was inhibited by about 75% by cocaine. The same degree of inhibition was obtained 4 h after 10 mg/kg guanethidine. In these experiments phenoxybenzamine did not reduce the residual (25%) uptake. 6 The reasons for differential rates of recovery of the endogenous NA content and the storage of [3H]-NA after guanethidine are discussed.