Central noradrenaline depletion during development and its effect on behaviour.

Although early depletion of noradrenaline is known to affect the morphological development of various structures in the brain, it is not clear what implications this has for adult behaviour. In the present study, 6-hydroxydopamine (6OHDA) was injected into the lateral ventricles of 12 day old rats, permanently destroying most of the noradrenergic innervation of the spinal cord and of all the brain areas examined except for the pons/medulla, and reducing the dopamine content of the cerebral cortex considerably. The noradrenaline content of the heart, as well as general developmental parameters such as food intake and body weight, were unaffected. Despite the extensive noradrenaline depletion during development, these rats' spatial memory--as determined in a radial maze task--was no worse than that of controls. In a lever-pressing task the 6OHDA treated rats made no more errors than did controls, but performed more slowly. The results indicate that at least some aspects of learning, memory and sensory-motor ability can develop normally when the noradrenergic innervation of the brain is largely destroyed.