The Role of Basal Forebrain in Rat Somatosensory Cortex: Impact on Cholinergic Innervation, Sensory Information Processing, and Tactile Discrimination
Abstract
The basal forebrain (BF)-neocortical pathway, and lesions disrupting it, have been used to study states of cortical arousal, neuronal responses to receptive-field stimulation, and learning and memory. Cholinergic neurons are a principal constituent of the BF and provide a major source of cortical acetylcholine (ACh). ACh isrecognized as an important element in normal cortical function since it enhances neural activity. The mechanisms of ACh-induced cortical enhancement are reviewed in Chapter 1. In Chapter 2 I present findings that stimulus-evoked metabolic activity, assessed by the 2-deoxyglucose (2-DG) technique, is reduced in ACh-depleted somatosensory cortex of rats. Background levels of 2-DG uptake are unaffected. In an effort to restore cortical ACh innervation and ameliorate the functional 2-DG deficit, transplants of ACh-rich embryonic BF were implanted into ACh-depleted rat cortex. Control grafts of embryonic neocortical tissue were placed into cortex of BF-lesioned animals. I report in Chapter 3 evidence that the implants established functional corrections. Regions of cortex within 2 mm from BF transplants contained (a) density of acetylcholinesterase (AChE)-stained fibers comparable to the opposite normal hemisphere, and (b) 2-DG uptake similar to that found in matched activated barrels in the contralateral hemisphere. Farther than 2 mm from the SF transplant, as well as throughout hemispheres with control neocortical grafts, (a) density of AChE staining is reduced, and (b) 2-DG uptake in barrels within these ACh-depleted territories is diminished from contralateralcounterparts. Chapter 4 examines the effect of cortical ACh depletion on a previously learned task of whisker sensory discrimination. Sham-Iesioned rats demonstrated no disruption of performance; animals with excitotoxic lesions of the SF exhibited transient impairments. The length of time to return to criteria positively correlated with amount of cortical ACh depletion.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 28, 1993
- Accession Number
- AD1011276
Entities
People
- Stella E. Jacobs
Organizations
- Uniformed Services University of the Health Sciences