An acute conditioned trace reflex was established in rats using a buzzer (5 sec) as a conditioned stimulus, and an electric shock (2.5 mA, 50 cycles per second) as an absolute stimulus. The latter lasted for one second and was applied through the grid floor of the training box.
The traces (time intervals between the end of the conditioned stimulus and the initiation of the absolute stimulus) were zero, 2 and 10 sec for the different control groups and for those treated with imipramine and chlorimipramine. A conditioned response was considered positive when the animal, in order to avoid the absolute stimulus, lifted one or both forelegs during the buzzer or the corresponding trace interval.
The number of conditioned responses was significantly lower in the zero trace control group than in the control groups trained with longer traces.
Imipramine and chlorimipramine (10 mg/kg) were administered by intraperitoneal injection 5 min before the conditioning session.
Both drugs significantly decreased the number of conditioned responses to all traces studied up to the same level. This shows that these drugs not only impaired acquisition, but also annulled the influence of trace duration upon it.
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Work supported by a fellowship (Dr. A. B. Merlo) and a grant No. 2914 of Consejo Nacional de Investigaciones Cientificas y Técnicas (Argentina) and another of Geigy, Argentina Laboratories.
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Merlo, A.B., Kuzniecki, N. Effect of imipramine and chlorimipramine on an acute instrumental trace conditioned reflex in rats. Psychopharmacologia 18, 124–128 (1970). https://doi.org/10.1007/BF00402392
- Conditioned Trace Reflex