Lithium Treatment Increases Norepinephrine Turnover in the Plasma of Healthy Subjects-Reply

In Reply.—  We read with interest the letter substantiating our finding that subchronic treatment of normal subjects with lithium is associated with enhanced release of NE. We demonstrated that 2 weeks' (but not 1 week's) lithium administration significantly increased levels of urinary NE, NMN, and a derived measure of NE release ([NE +NMN]/ [NE+NMN+VMA + MHPG], in which VMA indicates vanillylmandelic acid, and MHPG, 3-methoxy-4-hydroxyphenylglycol). Interestingly, lithium produced a nearsignificant 20% increase in levels of NE in plasma but did not affect levels of MHPG in plasma.In their study of seven healthy volunteers, Poirier-Littre et al observe that 3-week treatment with lithium results in significant increases in levels of total DOPEG (66%) and sulfate-conjugated DOPEG (71%) in plasma. These findings are of considerable interest because Goldstein et al¹ have recently demonstrated that DOPEG in plasma (DHPG) is derived primarily from sympathetic nerves and that procedures activating the sympathetic nervous system (eg,