The effect of single administration of reserpine on the response of the α₁-adrenergic agonist, phenylephrine, to the salivary secretion in mice was examined. Although the effect of reserpine (0.1-10.0㎎/kg, s. c.) alone on the salivary secretion was tested in anesthetized and unanesthetized mice injected intravenously, intraperitonealy and subcutaneously, respectively, no salivary secretion was observed under these conditions. Thirty min after administration of reserpine (0.1-10.0㎎/㎏), phenylephine (5.0㎎/kg, s. c.)-induced salivation significantly increased depending on dosage of reserpine. However, this increase of phenylephrine-induced salivation was inhibited by phenoxybenzamine (α-adrenergic blocking agent), not by propranolol (β-adrenergic blocking agent) and atropine (muscarinic cholinergic blocking agent). On the other hand, two days after administration of reserpine (1.0㎎/kg), phenylephrine-induced salivation significantly decreased by the level of about 41% compared to that of the mice without reserpine. However, seven days after administration, the altered responses to phenylephrine-induced salivation were not observed and showed the same level as that in mice without reserpine.

These results suggest that in mice singly pretreated with reserpine, phenylephrine can produce supersensitive and subsensitive responses to salivation, depending on the pretreatment time of reserpine.