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Open Access Effects of Single and Multiple Injections of Ketamine Hydrochloride on Serum Hormone Concentrations in Male Cynomolgus Monkeys

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Using simulated short- and long-term effect studies, we evaluated the effect of ketamine anesthesia on serum cortisol, testosterone, and immunoreactive luteinizing hormone (ILH) and bioactive LH (BioLH) concentrations in adult male cynomolgus monkeys. Cortisol, testosterone, and ILH were measured by use of radioimmunoassay, and BioLH was measured by use of a radioreceptor assay method. For the acute effect, the first group (eight monkeys) was given four successive intramuscular injections of ketamine (10, 5, 5, and 5 mg/kg of body weight at 0, 30, 60, and 110 min respectively). Blood samples were taken at 0, 15, 30, 45, 60, and 120 min. For the long-term effect, the second group (10 monkeys) was given a single injection of ketamine (10 mg/kg) once a week for 4 consecutive weeks. Blood samples were taken 5 to 10 min after each injection, then were used to determine the variation in hormone concentrations among the monkeys (inter-individual variation) and within each monkey (intra-individual variation). There were no statistically significant differences in serum cortisol, testosterone, ILH, and BioLH values between the first blood sample (before the ketamine injection) and sequential blood samples in monkeys of the first group. Although intra-individual variation in the hormones (i.e., hormonal change within each monkey) was not statistically significant, inter-individual variation (among the monkeys) was significantly (0.00001 < P < 0.033) different in monkeys of the second group. These results indicate that an adequate number of animals must be used to minimize animal-to-animal variability. Our results confirm that ketamine is a suitable anesthetic agent to immobilize male cynomolgus monkeys in experimental studies (short- and long-term studies) aimed at elucidating hormonal changes.

Document Type: Research Article

Affiliations: 1: Primate Research Unit, Department of Biology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand 2: Primate Research Institute, Kyoto University, Inuyama, Aichi, Japan 3: Tsukuba Primate Center, National Institute of Infectious Diseases, Tsukuba, Ibaraki, Japan 4: Tsukuba Primate Center, National Institute of Infectious Diseases, 1-Hachimandai, Tsukuba, Ibaraki 305, Japan

Publication date: 1998-06-01

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  • Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.

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