Overall objectives in proposed work: 1. To develop an intact animal model using operant techniques to provide an index of extent of narcosis over a continuum of subanesthetic concentrations. 2. To determine dose-response relationships for representative inhalation and intravenous agents. 3. To utilize the information obtained from (1) and (2) to study the phenomena of parallelism and additivity among these various agents. 4. To study effects of repeated anesthetic exposure in terms of tolerance. Goals for the coming year: To further elucidate mechanisms of anesthetic action by combining operant behavioral data with neuro-physiologic observations (EEG-recording; micro-injection of drugs into regional brain areas).