Psychotropic and neurotropic activity

Effect of season and temperature acclimation on the tissue catecholamine level and utilization in the frog, Rana temporaria

Male Wistar rats (TNO W. 70) were kept under controlled conditions of light and darkness (12¬12 h). The cardiac turnover of noradrenaline was determined with two methods, either by the decay of the specific activity after i.v. injection of3H-(−)-noradrenaline or by inhibition of the tyrosine-hydroxylase withd,l-α-methyl-p-tyrosine. During the 12 h of darkness at night the turnover was significantly faster than during daytime (12h illumination). Reversal of the light schedule shifted the noradrenaline turnover by approximately 12 h. The experiments show that the cardiac turnover of noradrenaline can be influenced by environmental lighting. This may be of importance when effects of drugs are studied.

Influence of light and darkness on the turnover of noradrenaline in the rat heart.

Rats were exposed to either a drug-induced state (1.0 mg/kg scopolamine) or an undrugged state (saline) at each stage of a three-stage procedure. They were first trained to lick a tube, then were exposed to classical fear conditioning in the absence of the tube, and finally were tested for conditioned suppression of licking. Animals tested at the midst of the dark period of the daily light/dark cycle displayed a failure of conditioned suppression if conditioning had occurred under the novel state; suppression was less consistently impaired in animals tested at the midst of the photoperiod. All animals exposed to a consistent drugged (or undrugged) state displayed conditioned suppression. Results suggest that experimental procedures frequently employed in studying drug manipulations of learning and memory may be biased against the transfer of training to the test situation. Scopolamine effects, often attributed to changes in learning or memory, may often represent a weakening in stimulus control of behavior resulting from transitions between drugged and undrugged states. Several factors are suggested as contributing to the diurnal difference in drug effects.

Scopolamine effects on conditioned suppression: Influence of diurnal cycle and transitions between normal and drugged states

UNIV SAO PAULO,SCH VET MED,APPL PHARMACOL & TOXICOL LAB,AV CORIFEU AZEVEDO MARQUES 2720,BR-05340 SAO PAULO,BRAZIL

J K Saelens

Papers

The influence of the adrenergic system on the 24-hour locomotor activity pattern in mice.