title: Autoradiographic estimation of the extent of reversible inactivation produced by microinjection of lidocaine and muscimol in the rat.
abstract: We used autoradiography to examine the extent of reversible inactivation produced by microinjection of lidocaine (40 micrograms/microliters saline) and muscimol (1 microgram/microliter saline). We measured intracortical spread of tracer amounts of labelled drug and local changes in uptake of [1-14C]glucose produced by the microinjection. The maximal average radii of regions of drug spread were 1.7 mm for both [14C]lidocaine and [3H]muscimol and were achieved within the first 20 min postinjection. The width of lidocaine injections decreased at longer postinjection times (30-60 min) but the width of muscimol injections remained relatively constant (30-120 min). Lidocaine radioactivity decreased faster from the injection site than muscimol radioactivity. Glucose autoradiograms showed a discrete region of maximally reduced glucose uptake (1.4 mm for lidocaine and 1.0 mm for muscimol) surrounded by a region of less reduced glucose uptake (up to approximately 3 mm). These findings suggest that, in the cortex, the effects of focal inactivation extend beyond the region of drug spread. Diffuse effects may be mediated of disfacilitation of cortico-cortical circuits.
authors.affiliation: Center for Neurobiology and Behavior, New York State Psychiatric Institute, College of Physicians and Surgeons, Columbia University, NY 10032.
authors.forename: J H
authors.initials: JH
authors.lastname: Martin
mesh_terms: D000818:Animals; D001345:Autoradiography; D002540:Cerebral Cortex / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D008012:Lidocaine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008297:Male; D008845:Microinjections; D009118:Muscimol / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051381:Rats; D014018:Tissue Distribution
chemical_list: D009118:Muscimol; D008012:Lidocaine; D005947:Glucose