Cannula implantation into the lateral ventricle does not adversely affect recognition or spatial working memory

Indwelling cannulas are often used to deliver pharmacological agents into the lateral ventricles of the brain to study their effects on memory and learning, yet little is known about the possible adverse effects of the cannulation itself. In this study, the effect of implanting an indwelling cannula into the right lateral ventricle was examined with respect to cognitive function and tissue damage in rats. Specifically, the cannula passed through sections of the primary motor (M1) and somatosensory hind limb (S1HL) cortices. One week following implantation, rats were impaired on the rotarod task, implying a deficit in fine motor control, likely caused by the passage of the cannula through the aforementioned cortical regions. Importantly, neither spatial working nor recognition memory was adversely affected. Histological examination showed immune cell activation only in the area immediately surrounding the cannulation site and not spreading to other brain regions. Both GFAP and CD-11b mRNA expression was elevated in the area immediately surrounding the cannulation site, but not in the contralateral hemisphere or the hippocampus. Neither of the inflammatory cytokines, TNF-α or IL-6, were upregulated in any region. These results show that cannulation into the lateral ventricle does not impair cognition and indicates that nootropic agents delivered via this method are enhancing normal memory rather than rescuing deficits caused by the surgery procedure.