AN EVALUATION OF THE EFFECTS OF MORPHINE ON ELECTROCORTICAL RECRUITMENT IN THE CAT AND DOG

¹ Department of Pharmacology, College of Medicine, University of Iowa, Iowa City, Iowa

The effects of morphine on recruiting responses in the cat and dog have been studied with several stimulating sites. These sites were the thalamic nuclei centrum medianum, medialis dorsalis, centralis medialis and ventralis anterior. The recording sites were on the anterior sigmoid, posterior sigmoid, anterior ectosylvian, posterior lateral and posterior suprasylvian gyri, as well as in the nucleus ventralis anterior. The morphine dosage was 1, 2 and 4 mg/kg. It was found that recruiting responses generally were depressed in the cat after morphine, although this was not statistically significant in all cases. In the dog recruiting responses were likewise generally depressed, although a tendency toward enhancement was sometimes seen. However, the most striking effect of morphine on recruiting responses in the dog was an alteration in the recruitment pattern (waxing and waning of the response). This was not observed in the cat. Presumptive evidence is presented on which are based working hypotheses concerning the effects of morphine on the diffuse thalamocortical projection system.

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