High performing rats are more sensitive toward catecholaminergic activity enhancer (CAE) compounds than their low performing peers

Abstract

Two breeds of rats, Charles River Wistar [Crl (Wi) Br.] and HSD Wistar [Wistar per LATI (Budapest) Br.], with remarkable difference in learning performance were selected. The rats were trained in the shuttle box with 100 trials per day and the number of conditioned avoidance responses (CARs), the escape failures (EFs) to the unconditioned stimulus and the intersignal reactions (IRs) were counted and evaluated by multi-way analysis of variance (ANOVA). Rats of the Crl (Wi) breed proved to be the ‘low performing’ (LP) animals and rats of the Wistar per LATI (Budapest) breed the ‘high performing’ (HP) ones. The HP rats produced higher number of CARs (p < 0.001), lower number of EFs (p < 0.05) and higher number of IRs (p < 0.01) than their LP peers. Significantly higher amounts of noradrenaline from the locus coeruleus and serotonin from the raphe were released in the HP than in the LP rats (p < 0.01). There was no difference between HP and LP rats in the amount of dopamine released from the striatum, the substantia nigra and the tuberculum olfactorium. The catecholaminergic activity enhancer (CAE) substance, l-phenyl-2-propylaminopentane HCl,, [(−)PPAP], which enhances action potentialtransmitter release coupling in the catecholaminergic neurons, fully antagonized in a dose of 1 mg/kg, tetrabenazme-induced learning depression in HP rats and this dose was ineffective in LP rats. The findings were regarded as further support for the view that endogenous CAE substances regulate catecholaminergic activity in the brain and (−)PPAP acts via this regulation.