Persistence of classical conditioned heart rate after extensive lesions of the striatum in rats

The participation of the Corpus Striatum in the acquisition and maintenance of conditioned heart rate was determined. After a 25 min period of adaptation in a sound attenuated chamber 8 rats were presented with a single association of a sound (CS) and a nociceptive stimulus (US) applied to the paws, while electrocardiographic recordings were made. Twenty-four hours later the sole application of CS produced a significant increment in the heart rate. The same results were obtained in 8 rats that were previously electrolytically lesioned in the corpus striatum. In another 8 rats the electrolytic lesions were performed after the acquisition session. These rats also showed the increment in heart rate produced by the CS during the testing session. Finally, in 8 more rats in which the association of CS-US was inversed no conditioned response was obtained. The electrolytic lesions comprised several milimeters of the corpus striatum involving the anterior medial and posterior part and even extended to surrounding areas. Nevertheless the animals were able to acquire and retain the vegetative conditioned response.