Subjects may not take medications that can affect somatostatin levels, such as antidepressants, benzodiazepines, neuromodulators (e.g., cholinergic, alpha/beta adrenergic), oral contraceptives (BCP), steroid hormones (with the exception of estrogen replacement therapy -ERT-, for which subjects will be matched), immunomodulators, anticonvulsants (e.g., carbamazepine), cimetidine -Tagamet® (Registered Trademark)-, herbal remedies (because of their variable substance content). Subjects may not take drugs affecting gastrin secretion: antacids (e.g., Maalox® (Registered Trademark), Mylanta® (Registered Trademark), H(2) receptor antagonists (e.g., famotidine -Pepcid® (Registered Trademark)-, ranitidine -Zantac® (Registered Trademark)-), cathecolamines, atropine, haloperidol. To become eligible, subjects should be able to safely discontinue these medications at least one month prior to phase I. Antacids, H(2) antagonists and neuromodulators (e.g., Salagen) may be discontinued 2 days prior to phase I.