Fig. 1.

Concentration-dependent effects of ketamine on the secretory responses of catecholamines (CA) from the perfused rat adrenal glands evoked by acetylcholine (ACh, Upper) and by high K⁺ (Lower). CA secretion by a single injection of ACh (5.32×10^-3 M) or K⁺ (56 mM) in a volume of 0.05 ml was evoked at 15 min intervals after preloading with 30, 100 and 300 µM of ketamine, respectively, for 60 min as indicated at an arrow mark. Numbers in the parenthesis indicate number of rat adrenal glands. Vertical bars on the columns represent the standard error of the mean (S.E.M.). Ordinate: the amounts of CA secreted from the adrenal gland (% of control). Abscissa: collection time of perfusate (min). Statistical difference was obtained by comparing the corresponding control with each concentration-pretreated group of ketamine. Pefusates induced by ACh and high K⁺ were collected for 4 minutes, respectively. ^**p<0.01.