Plasma Free Corticosteroid Response to Faradic Stimulation in the Rat

If the corticotrophin-releasing effect of emotional and sensory stimuli is wellknown (De Groot & Harris, 1950, Fortier, 1951, Mialhe-Voloss, 1958), the pattern, amplitude and duration of the pituitary-adrenocortical response to these stimuli have not yet been fully described. Hence the following report, based on plasma free corticosteroid determinations, in the rat, at progressively later intervals following the onset of an electrical stimulus of short duration. 38 male Sprague-Dawley rats (225–240 gm. B. W.) were caged singly and acclimatized for two weeks to laboratory conditions (constant lighting and temperature (25 ± 1° C); Purina Fox-Chow and water ad lib.). Of these, 10 were used as controls, and 28, as experimentals. Special care was taken to prevent any disturbance of the animals, for a period of 12 hours prior to the experiment. On seven different days, 4 rats were separately subjected, for 150 seconds, to alternating (on and off) periods of