Noradrenaline and sensory preconditioning in the rat.

Two experiments were performed to investigate the effect of noradrenaline (NA) depletion following systemic administration of the neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4; 50 mg/kg, ip) on sensory preconditioning in the rat. For sensory preconditioning, a taste (saccharin, CS2) and a special type of drinking bottle (noisy bottle) were paired during Phase 1. During Phase 2, the noisy bottle (CS1) was paired with lithium chloride, and, finally, during Phase 3 the aversion to saccharin (CS2) was tested for in saccharin preference tests. The DSP4 treatment disrupted rats' ability to form sensory preconditioning, and this effect could not be explained on the basis of enhanced neophobia, stimulus generalization, or a deficit in first-order conditioning in DSP4-treated rats. These findings are closely related to these and other issues of associative learning such as contextual control of latent inhibition and extinction. The evidence from the present data suggests that NA-depleted rats fail to form associations between the CS1 and CS2 during sensory preconditioning and, as such, are consistent with other data from various compound conditioning experiments on the functional role of NA in learning and memory.