CHAPTER9 LABORATORY ANIMALS*...2.1. LAB ANIMAL HUSBANDRY • Lab$animal$husbandry:$righthousing$and$environmental$condi6ons,$ good$health,$good$welfare$ CAGE% MATES% CAGE% CAGE% STRUCTURE%

CHAPTER 9

LABORATORY ANIMALS

2. REFINEMENT

“Refine experiments to cause the minimum pain, distress and las4ng harm”

2.1. LAB ANIMAL HUSBANDRY

• Lab animal husbandry: right housing and environmental condi6ons, good health, good welfare

CAGE MATES

CAGE STRUCTURE CAGE

DIMENSIONS BEDDING

SCENTS

SOUNDS

LIGHT

HUMIDITY TEMPERATURE

PATHOGENS

OTHER SPECIES

PEOPLE

FOOD & WATER

VENTILATION NH3, CO2


• Microbiological status of lab animals • Germ-‐free: completely free from micro-‐organisms • GnotobioEc: harbour a fully known microflora • Specific pathogen-‐free (SPF): free from a number of specified (poten6ally) pathogenic micro-‐organisms • ConvenEonal: microbiological status unknown and uncontrolled

• Sources of infec6on: animals, staff, biological materials, insects and vermin • Disinfec6on and sterilisa6on


• Examina6on of an animal’s physical appearance is essen6al for health and welfare assessment. When evalua6ng an animal’s physical condi6on, one should look at: •  Body condi6on (“fit not fat”)

hMp://www.ahwla.org.uk/site/Tutorials.html


•  Body condi6on (“fit not fat”) •  Changes in body shape •  Posture •  Fur and feathers •  Facial expression •  Skin •  Mucous membranes •  Eyes, ears, nose, mouth, perineum

2.2. ENRICHMENT

• Environmental enrichment = method employed to increase the biological relevance of a cap6ve environment with a view to improve overall welfare •  Used to combat boredom and frustra6on, encourage explora6on, normal foraging and to reduce destruc6ve and aberrant behaviours

• Social enrichment: intra-‐ and interspecific interac6ons (e.g. contact with cage mates and humans)

2.2. ENRICHMENT

• Dietary enrichment: different ways of presen6ng food; novel foods; hay or straw for foraging • Sensory enrichment: auditory (sounds), visual, olfactory (smells)

2.2. ENRICHMENT

• Physical enrichment: cage dimensions and design, novel toys, increasing the complexity of an enclosure

2.2. ENRICHMENT

• The recovery environment can contribute posi6vely to aMenuate the need for pain relief in animals submiMed to invasive procedures.

(Pham et al., Physiol. Behav. 2010, 99: 663-‐668)

Non-‐enriched, isolated

Enriched, isolated

Non-‐enriched, grouped

Enriched, grouped

(Cao et al., Cell 2010, 142: 52-‐64)

2.2. ENRICHMENT

• Simple environmental enrichment (EE) decreases figh6ng in aggressive males, decreases aggression in certain inbred mouse strains, decreases barbering in mice, makes mice more easier to handle, etc. • Does not affect outcomes of experiments

2.4. NON-INVASIVE METHODS

• CT (computed tomography) or CAT (computed axial tomography) scan •  Based on differences in damping of X rays through different 6ssues; mostly used for 6ssues with high density (e.g. bone) •  Several images are taken and processed by the computer •  Painless (animal is anaesthe6sed) •  If animals are followed for longer periods of 6me, the high radia6on level may cause tumours to develop.


• CT (computed tomography) or CAT (computed axial tomography) scan


• PET (positron emission tomography) scan • Makes use of tracer; decay of tracer results in emission of two photons that are detected in two direc6ons •  Very sensi6ve, but gives bad anatomical detail (usually combined with CT) •  Painless


• MRI (magne6c resonance imaging) •  Relies on powerful magne6c fields and radiofrequency pulses • MRI provides good contrast between the different soe 6ssues of the body → useful for imaging brain, muscles, heart, tumours

2.5.1. ANAESTHESIA

• Anaesthesia = reversible lack of awareness • Pharmacologically induced and reversible state of amnesia, analgesia, loss of responsiveness, loss of skeletal muscle reflexes or decreased fight-‐or-‐flight response, or all simultaneously. • This allows pa6ents to undergo surgery and other procedures without the distress and pain they would otherwise experience.

2.5.1. ANAESTHESIA

• General anaesthesia: reversible repression of central nervous system • Analgesia — loss of response to pain • Amnesia — loss of memory •  Immobility — loss of motor reflexes, skeletal muscle relaxa6on • Hypnosis — loss of consciousness

• Single anaesthe6c (e.g. pento-‐barbital, ketamine) or combina6on of different pharmaceu6cals • Mode of ac6on of general anaesthe6cs not well understood; affect the GABA and NMDA systems in the brain

2.5.1. ANAESTHESIA

• Phases of general anaesthesia:

PREPARATION (PREANAESTHESIA) (PREMEDICATION/SEDATION)

INTRODUCTION (INDUCTION)

MAINTENANCE

RECOVERY (EMERGENCE)

2.5.1. ANAESTHESIA

• Anaesthe6c premedicaEon consists of a drug or combina6on of drugs that serve to complement or otherwise improve the quality of the anaesthe6c. • e.g. reduce saliva secre6on, bradycardia, bronchoconstric6on

• SedaEon: tranquilising (to calm down nervous animals) • e.g. benzodiazepines (like diazepam, midazolam): enhance effects of GABA •  Anxioly6c (= fear-‐reducing) •  Seda6ve •  Hypno6c •  An6convulsant • Muscle relaxant •  Amnesic

2.5.1. ANAESTHESIA

• Stages of anaesthesia • Stage I: InducEon stage

•  Period between the ini6al administra6on of the induc6on agents and loss of consciousness; animal progresses from analgesia without amnesia to analgesia with amnesia (fear, urina6on, defaeca6on, struggling, disorienta6on)

• Stage II: Excitement stage •  Respiratory and heart rate may become irregular, many reflexes are enhanced, increased muscle tension, pupil dila6on, increased tear and saliva produc6on, vocalisa6on

• Stage III: Surgical anaesthesia •  Concentra6on of anaesthe6c in brain increases: respiratory rate and depth decrease, pupil narrower, eyelid and cornea reflexes slower and disappear, muscle tension and toe reflex decrease → reflexes absent, anaesthesia sufficiently deep

• Stage IV: Overdose •  Vital brain centres repressed, respiratory arrest, circulatory collapse, death within 1-‐5 mins

2.5.1. ANAESTHESIA

• Judge depth of anaesthesia by • Respiratory rate and depth • Heart rate • Reac6on to pain s6muli • Tes6ng of reflexes

•  Righ6ng (turn-‐around) reflex

•  Eyelid reflex (= palpebral or blink

reflex)

•  Swallowing reflex

•  Pupil reflex (= pupillary light

reflex)

•  Tail pinch reflex and toe reflex in

mice and rats

2.5.1. ANAESTHESIA

• Local anaesthesia •  To induce the absence of sensa6on in part of the body, generally for the aim of inducing local analgesia (= local insensi6vity to pain); structurally related to cocaine

• Regional anaesthesia •  Affec6ng only a large part of the body, such as a limb •  Plexus block: complete innerva6on area of nerve •  Epidural block: complex of nerves •  Diagnosis of navicular disease in horses, lameness

•  Influence on physiological processes outside anaesthe6sed area minimal; safer in many situa6ons • DissociaEve anaesthesia

•  Reduces or blocks signals to the conscious mind from other parts of the brain → animal no longer feels connected to and aware of its environment •  Hallucinogenic, amnesia, analgesia • Most used: ketamine

2.5.1. ANAESTHESIA

•  Important: •  Ill animals have a bigger chance to drop out during anaesthesia • Anaesthe6cs influence physiological parameters (blood pressure, heart rate, respira6on, thermoregula6on) → experiment! •  Interac6on of anaesthe6c with other pharmaceu6cals (e.g. an6bio6cs) • Long-‐las6ng anaesthesia → hypothermia

2.5.1. ANAESTHESIA

• Response of the animal to the administered anaesthe6cs depends on species, age, strain, weight, basal metabolism, sex, fat %, feeding condi6on, heath condi6on, previous exposure to pharmaceu6cals • Doses of anaesthe6cs are not the same for all species (par6ally because of varia6on in body composi6on)! • Species-‐specific reac6ons, e.g.

•  Hamsters are less sensi6ve to Nembutal than other rodents. • Mice and cats react excited to morphine. •  About 30% of rabbits does not respond to atropine premedica6on.

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CHAPTER9 LABORATORY ANIMALS*...2.1. LAB ANIMAL HUSBANDRY • Lab$animal$husbandry:$righthousing$and$environmental$condi6ons,$ good$health,$good$welfare$ CAGE% MATES% CAGE% CAGE% STRUCTURE%