Supersensitivity of salivation in response to pilocarpine after withdrawal of chronically administered hyoscine in the mouse

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Abstract
Summary: . The duration of the effect of a single large dose of hyoscine, in reducing the salivary response of mice to pilocarpine, was established as less than 66 hours. . Supersensitivity was observed, after daily oral dosing with hyoscine, in the increased salivation of mice in response to pilocarpine injected at least 66 h after withdrawing hyoscine. . The minimum duration of pretreatment with hyoscine that resulted in supersensitivity was 5 days. The daily dose was more effective if divided. . The period after withdrawal for which supersensitivity could be detected was 6 days. . The maximum salivary response to pilocarpine was increased by chronic hyoscine pretreatment. . The antagonism of a single dose of hyoscine to pilocarpine salivation, as expressed by the dose‐ratio of pilocarpine, was not altered by chronic hyoscine pre‐treatment.