VALIDATION OF A FUNCTIONAL OBSERVATIONAL BATTERY IN THE MINIPIG FOR REGULATORY NEUROTOXICITY ASSESSMENTS

Scientific Poster
Validation of a Functional Observational Battery in the Minipig for Regulatory Neurotoxicity Assessments - SciPos115

Abstract

Background: A functional observational battery (FOB) is recommended as the first-tier neurotoxicity screening in the preclinical safety pharmacology testing guidelines. The minipig has increasingly been used in regulatory toxicology studies; however, no current FOB protocol is available for the neurotoxicity testing in this species.

Purpose: To validate a minipig functional observational battery protocol.

Methods: A crossover study with Sinclair minipigs was performed to capture effects of amphetamine, ketamine and diazepam. The minipigs were observed in their home cage, were video recorded for 10 minutes in a confined open field and went through a neurologic examination.

Results: Both ketamine and diazepam treated minipigs showed reduced interests in environmental changes and increased exploration interests and had muscular malfunction and gaits impairment. On the other hand, unique and even opposite effects were also observed between ketamine and diazepam, which might reflect their unique mechanisms of action in treated minipigs. Effects of ketamine and diazepam were consistent with their roles in suppressing central nervous system (CNS) functions. Amphetamine is a CNS stimulant, which promotes dopamine-associated brain activities. Amphetamine treated minipigs were consistently shown to be hyperactive and to display increased interest to environmental changes and reduced exploring activities. Amphetamine also increased locomotion and induced biphasic behavior effects in the treated animals. The shared effects of ketamine and diazepam might result from their interference with dopamine functions in CNS, in contrast to those of amphetamine.

Conclusion: The Sinclair minipig is suitable for functional observational battery (FOB) evaluation of chemicals in preclinical safety pharmacology testing, and a reproducible quantitative approach is described.

Keywords: Neurotoxicity Testing, Functional Observational Battery, Sinclair Minipig, Amphetamine, Ketamine, Diazepam

Authors

Miao Zhong1, Amber Fuller1, Chris Hanks1, Derek Brocksmith2, Jason Liu1, Shayne Gad3, Guy Bouchard1,2, & Alain Stricker-Krongrad1*
¹Sinclair Research Center LLC; 2Sinclair Bio Resources, LLC; 3Gad Consulting Services; *Corresponding Author

Experimental Methods

Animals:

  • Sinclair minipigs (4 male)
  • Age: 7 - 10 months

Procedure:

  • Acclimate for 7 days
  • Weekly body weight
  • Intramuscular dosing saline (vehicle), amphetamine, ketamine, & diazepam (test article)
  • Each animal had no more than one test article treatment in each week. Functional Observational

Battery:

  • Specification of FOB parameters: 1=normal behavior/response, 2 & above=abnormal behavior/response, 0=absence of normal behavior/response.
  • One-time observation of animals in their home cages
  • Open field observation: video-recorded for 10 minutes in an 8 × 8 feet enclosure
  • Neurological examination: examined in a sling or on the ground by a clinical veterinarian

Summary

  • Variability (moderate to high) was observed only in 12 continuous and count variables.
  • Variations derived from individual animals were higher than those from the repeated daily observations for most of the 12 parameters.
  • Both ketamine and diazepam were shown to reduce the interest in environmental changes and to increase exploration interests of treated minipigs, as well as to cause muscular malfunction and gait impairment.
  • Ketamine was shown to impair pupillary reflex and to induce nystagmus and to affect proprioceptive positioning whereas diazepam to impair blink reflex in multiple animals.
  • Consciousness and alertness were compromised in diazepam treated but not in ketamine treated animals.
  • Ketamine increased gland secretion and heart and respiration rates, while diazepam decreased respiration.
  • Unlike ketamine which reduced desire of motility, diazepam increased ambulation and bouts of locomotion in treated animals.
  • Amphetamine increased the interest of treated minipigs to environmental changes and reduced exploring activities.
  • Amphetamine increased the desire of motility and induced biphasic effect at low and high doses in a number of behavior parameters.

Download the poster to view tables and figures

References

  1. Swindle MM. Vet. Pathol (2012) 49(2): 344.

Download this poster