COMMON

LABORATORY

ANIMALS

USED IN

DRUG

DEVELOPMENT

BACKGROUND

• The first major reference to animal testing occurred in the late nineteenth century

when Louis Pasteur administered anthrax to sheep and showed the importance of

vaccines with his germ theory.

• Charles Darwin's evolutionary theory in the mid 1850s also served to suggest that

animals could serve as effective models to facilitate biological understanding in

humans.

• Other cases of animal testing include psychological experiments such as the one by

Ivan Pavlov in the late nineteenth century. He conducted experiments on dogs to

demonstrate how dogs could be conditioned with regards to memory and repetitive

tasks.

• An enormous breakthrough came in 1922 when animal testing allowed for insulin

to be isolated from dogs. In the 1930s, modern anaesthetics and antibiotics were

developed from the use of animal testing. In addition, anticoagulants and kidney

dialysis, both life-saving treatments, were introduced following animal testing.

• The 1950s saw animal testing aiding in the development of vaccines. The other

developments include many potent cancer drugs as well as drugs for HIV that were

developed in the latter quarter of the twentieth century

Why are animals used in clinical

research?

• The basic cell processes are the same in all animals, and they perform similar vital functions such as breathing, digestion, movement, sight, hearing and reproduction

• Simple animals can be used to study complex biological systems such as the nervous or immune systems, which follow the same basic organisation and function in all animals.

To advance scientific

understanding

• Studying disease mechanisms in animal models leads directly to the development of new technologies and medicines that benefit both humans and animals.

• While contributing to our understanding of diseases, animal models enable researchers to explore potential therapies in ways which would be impossible in humans.

• Animals which are altered to create models of disease are known as induced models.

• These animal models help researchers understand what happens in the body following this type of damage, and have been used in the development of new therapies.

• Recent advances in genetic technology have allowed the development of transgenic animals, which have new genes inserted into their DNA, allowing them to develop human diseases which do not naturally affect them.

As models to study disease

• Once researchers learn more about a particular disease, animals are used to develop and test these potential therapies as part of the applied research process.

• Data from animal studies is essential before new therapeutic techniques and surgical procedures can be tested on human patients.

• For example, medicines for Parkinson's disease have been developed using animal models with induced Parkinson's-like symptoms.

• Diagnostic tools such as scanners, and implants such as pacemakers are safe and effective only because they were developed and tested in animals.

• Many surgical techniques, such as open heart surgery and heart transplants, rely on methods and equipment that were developed using animals.

To develop and test potential forms of treatment

• New medicines require testing because researchers must measure both the beneficial and the harmful effects of a compound on an organism.

• The animal tests provide data on efficacy and safety of a new compound. They not only identify potential safety concerns, but also determine the doses which will be given to volunteers and patients during the first human trials.

• Testing on animals also serves to protect consumers, workers and the environment from the harmful effects of chemicals.

To protect and ensure

the safety of people,

animals and the

environment

ANIMALS USED IN RESEARCH

MAMMALS

RODENTS(mice,rats,guinea pigs,hamsters, gebrils)

NON RODENTS(rabbit, dog,cat,monkey,pig ,etc)

MISCELLANEOUS Frog,pigeon,zebra fish,

chicken,etc

RODENT MAMMALS

USED IN DRUG

DEVELOPMENT

RAT(Rattus norvegicus)

Rats have been useful for research in the following fields-

• Study of analgesics and anticonvulsants.

• Study of oestrus cycle, mating behaviour and lactation.

• Gastric acid secretion

• Hepatotoxicity studies

• Study on mast cells

• Bioassay of various hormones, such as insulin, oxytocin, vasopressin .

• Rats are better at removing toxins from their bodies than humans, so it may be

possible to refine the use of rats in toxicology studies.

• Rat brain tissue is extensively employed in radio-receptor ligand studies.

WISTAR RATS

These were developed at the Wistar Institute in 1906 and is notably the first rat developed to serve as a model organism.

The Wistar rat is currently one of the most popular rats used for laboratory research.

It is characterized by its wide head, long ears, and having a tail length that is always less than the body length.

SPRAGUE DAWLEY RATS

These rats typically have increased tail to body length ratio as compared to Wistar rats.

Long-Evans rat

They are utilized as a multipurpose

model organism, frequently in

behavioral and obesity research

ZUCKER RATS –

They are genetically modified rats used

to study obesity and hypertension.

BIOBREEDING RATS –

They are used as models to study

autoimmune type 1 diabetes

HAIRLESS RATS –

They are use to study compromised immune systems and genetic kidney diseases.

DIFFERENCE BETWEEN RATS AND MICE

• The rat is much larger in size and has greater body wieght as

compared to the mouse.

• The mouse has a pointed face when compared to the rat.

• The rat has a thick and heavy tail. On the other hand, a mouse

has a very thin tail

• The rat has a higher pair of chromosomes, ie 22 pairs. On the

contrary, the mouse has only a 20 pairs.

• The rats have a longer gestation period compared with the

mice.

MICE(Mus musculus) • They are most widely used in clinical

research as they are small, inexpensive and

easy to handle .

• Mice are used in a vast range of experiments,

many of which are classified as fundamental

research, investigating the physiology of

mammals.

• They have similar reproductive and nervous

systems to humans, and suffer from same

diseases such as cancer, diabetes and even

anxiety

• Their short life span and fast reproductive

rate, makes it possible to investigate

biological processes at all stages of the life

cycle.

• Swiss albino mice are the most commonly

used species.

EXPERIMENTAL USES

• Toxicological studies

• Teratogenicity studies

• Bioassay of insulin, screening of analgesic and

anticonvulsant drugs

• Screening of chemotherapeutic agents

• Studies related to genetics and cancer research

• Drug action on CNS

GUINEA PIG(Cavia porcellus)

• Guinea pigs have biological

similarities to humans, which

make them useful in many fields

of research.

• Vitamin C was discovered

through research on guinea pigs.

• Their serum contains enzyme

Aspariginase which shows anti-

leukaemic action.

They were also crucial to the

development of :

• Vaccines for diphtheria, TB,etc

• Evaluation of local anaesthetics

• Antibiotics,

• Histamine and antihistamines

• Anticoagulants

• Bronchodilators

• Bioassay of Digitalis.

Guinea pig tissue

• Guinea pig blood components and isolated organ preparations such as lung and intestines are extensively used in research to develop new medicines.

• Terminal portion of ileum used for screening spasmodic and anti spasmodic agents.

• They were important in the discovery and early development of beta blockers to treat high blood pressure and drugs to treat stomach ulcers.

• Numerous developments have used their intestine for example the anti-nausea drugs used by cancer patients and the identification of naturally occurring pain killing substances known as enkephalins.

• Allergies and respiratory diseases

• The extreme allergic reaction, anaphylactic shock has been studied extensively in guinea pigs.

• Their airway is sensitive to allergens, so it has been widely used in asthma studies. The inhaled medications that are the mainstays of asthma treatment were developed using guinea pigs as were orally-active drugs for asthma such as montelukast.

• They are also used in the testing of vaccines against anthrax and new medicines to treat drug-resistant tuberculosis.

• Also used to test for allergic skin reactions due to their skin sensitivity.

• Nutritional research

Along with Vitamin C , guinea pigs also need high levels of

folic acid, thiamine, arginine and potassium, which make them

useful in nutrition studies.

• They also carry most of their plasma cholesterol in low density

lipoprotein, so they are also useful in the study of cholesterol

and lipoprotein metabolism.

• Infectious Diseases

• The German scientist Robert Koch used guinea pigs to discover that TB was caused by the bacterium Mycobacterium tuberculosis.

• In 1919 research showed that inoculation of guinea pigs with a small amount of blood from Yellow Fever patients produced a mild reaction in the animals. The same animals were later resistant to infection with Leptospira icteroides

• The animals which had received no previous inoculation, or which had been inoculated with blood from malaria patients, died.

• Safety testing

• The long gestation period of 59–72 days and mature central nervous system at birth means that guinea pigs are important in safety testing, particularly to prevent birth defects .

GERBIL(Meriones unguiculatus)

• Also known as sand rats or jirds.

Their size lies between that of rats

and mice.

• Used as research animal in stroke,

epilepsy and heart diseases.

• Useful in study of parasitic and

bacterial infections.

• Used in auditory studies because

hearing curve is similar to that of

humans.

HAMSTER(Mesocricetus Auratus)

• Third commonly used laboratory

animal.

• Two species are commonly used-

Golden or syrian hamster

Chinese hamster

• Hamsters are used extensively in onco virus, Influenza virus and

Respiratory Syncitical Virus (RSV) studies and vaccine production.

• Their cheek pouches do not have lymphatic drainage and hence they are

ideal sites for tissue transplants.

• Syrian Hamster is most commonly used for biomedical research because of

ease of availability.

• European Hamster is more suitable model for highly concentrated and

prolonged smoke inhalation studies.

• Chinese Hamster is suitable for cytogenesis research.

NON – RODENT

MAMMALS USED IN

DRUG DEVELOPMENT

RABBIT(Oryctolagus cuniculus) • Historically, Louis Pasteur used

rabbits to develop the rabies vaccine.

• Studies in rabbits are key to many aspects of medical research, including cancer, glaucoma, eye and ear infections, skin conditions, diabetes and emphysema.

• The rabbit has been important in the study of cardiovascular diseases , particularly hypertension and atherosclerosis.

• Enzyme atropine esterase is present in rabbit liver and plasma so it can tolerate large doses of belladona (atropine)

RABBITS HAVE BEEN USED FOR RESEARCH IN FOLLOWING FIELDS -

• Pyrogen testing

• Bioassay of anti-diabetic drugs

• Screening of agents affecting capillary permeability

• Drugs used in glaucoma

• Studies related to antifertility agents

• It has simple cardiac tissue free of connective tissue and hence is the animal of

choice for cardiac studies.

• The rabbit has provided an excellent model system to simulate the response of

human tissue to the radiation produced by surgical lasers.

• Laser advancements made possible by research on rabbits include eye surgery and

the dissolving of plaque build-up on the walls of arteries.

• TESTING OF COSMETICS USING DRAIZE TEST –

• Rabbits - particularly albino rabbits - are commonly used in testing for cosmetics

and other chemicals, where they are used to perform the Draize test. This test

involves the substance being placed on the rabbit's eyes or skin, which are then

observed for redness, irritation or any other damage.

MONKEY(Macaca mulatta)

• Used as primate model to study drug metabolism .

• Suitable for undertaking psycho-pharmacological studies.

• Uterus resembles that of humans, showing regular menstrual cycles.

• Best for studying drugs acting on CNS, CVS, GIT and fertility.

CAT(Felis catus) Since 1898, cats have contributed to the

study of emotion, cardiac disease, spinal

cord injury, cataract surgery, glaucoma,

lupus, diabetes, spina bifida and more.

• Cats are mainly used as models to study

sensory systems and neuroscience.

• Cats have a distinct nictitating membrane

used for studying ganglionic drugs.

• Cats have been used to study neurological

problems, such as epilepsy, deafness, and

vision problems .

Studies on Aging -

• The relatively long life span of cats makes

it possible to observe the slower and more

subtle effects of aging.

DOG(Canis familiaris)

• Most preferred large experimental

animal due to small alimentary tract

and ease of training.

• Used for studying various anti-

arrythmic, cardiovascular drugs.

• Mongrel and Beagles are the most

preferred due to manageable size,

moderate hair coat and docile nature

.

• Good model for Diabetes Mellitus,

Ulcerative Colitis, Open heart

surgery and organ transplantation.

OTHER ANIMALS

USED IN DRUG

DEVELOPMENT

FROG(Rana tigrina)

The study of frog muscles in the

1920's led to the discovery of

neurotransmitter acetylcholine .

Frog eggs are large and resilient

hence, used to train cell biologists in

genetic manipulation.

Studying embryonic development

The African clawed frog, Xenopus

laevis, is often used in early studies

of development. They have been

useful for studying early events, such

as the formation of the neural plate.

African clawed frog

• When genetics is an important part of the study , Xenopus tropicalis is the preferred species as they have a shorter breeding cycle, and have diploid cells.

A new type of antibiotic

• Another peculiarity of frogs is their ability to survive in bacteria-filled water without wounds becoming infected.

• Studying this property of Xenopus laevis, Michael Zasloff, discovered a new class of antibiotic compounds in their skin called magainins . They may provide a future solution to the problem of antibiotic-resistant bacteria.

• Recently, the first transparent frog was developed a Horoshima University in Japan , making it a great model for studying the aspects of human physiology .

• Transparent frogs will make it easier and cheaper to observe the development and progress of cancer, the growth and aging of internal organs, and the effects of chemicals on organs.

ZEBRA FISH(Danio reiro)

• It is an excellent model for

studying development in

vertebrates.

• The embryos develop externally to

the mother and are transparent,

hence can be easily viewed and

manipulated.

• The organization of the embryo is

simple, and they develop quickly

• They are suitable for genetic

models of human diseases. Genes

responsible for human diseases

have equivalents in the zebra fish.

CREATING TRANSGENIC

MODELS • Zebra fish mutants are currently used to model many human diseases,

including Alzheimer’s disease, congenital heart disease, polycystic kidney

disease , cancers and development of the nervous system.

• Its aim is to use the zebra fish to produce new disease models, find new

drug targets and learn more about the gene-regulation pathways involved

in human development and disease.

• Using genetic techniques, a team of researchers stimulated the

development of a type of leukaemia - T cell acute lymphoblastic

leukaemia - in the fish.

• Creating zebra fish which develop leukaemia will enable researchers to

test the effect of various anti-cancer agents.

CHICKEN (Gallus gallus) Chicken are used when birds are needed for a physiological study.

They are easy to keep, and have been bred domestically for many years.

Since chickens are vertebrates, their developmental process is quite similar to that of humans.

Chick embryos are being used to model atrial septal defect condition, because like humans, they have a four-chambered heart.

Chick embryo used to

study the

development of atrial

septal defect

PIGEON (Columbia livia)

• Pigeons are good screening

models for anti-emetic drugs.

• They also find application in

bioassay of prolactin.

• Used for screening of intravenous

anaesthetics.

• Used for standardisation of

cardiac glycosides.

UNFORTUNATE ASPECT

OF ANIMAL USE IN DRUG

DEVELOPMENT

Animals are killed or kept in captivity:

In animal testing, countless animals are experimented on and then killed after their

use. Others are injured and will still live the remainder of their lives in captivity.

• Some substances tested, may never be used for anything useful:

The unfortunate aspect is that many of these animals received tests for substances

that will never actually see approval or public consumption and use. It is this aspect

of animal testing that many view as a major negative against the practice, as it seems

that the animal died in vain because no direct benefit to humans occurred.

• It is very expensive:

Animal testing generally costs an enormous amount of money, as the animals must

be fed, housed, cared for and treated with drugs or a similar experimental substance.

In addition , animal testing may occur more than once and over the course of

months, which means that additional costs are incurred. The price of animals

themselves must also be factored into the equation.

• Animals and humans are never exactly the same:

There is also an argument that the reaction of a drug in an animal's

body is quite different from the reaction in a human.

The belief that since animals are in an unnatural environment, they

will be under stress. Therefore, they won't react to the drugs in the

same way compared to their potential reaction in a natural

environment. This argument further weakens the validity of animal

experimentation.

ALTERNATIVE

APPROACHES TO

ANIMAL TESTING

• While the scientific community generally supports the use of animals to further our knowledge of health and medicine, they still acknowledge the need for alternatives to reduce animal suffering. This is accomplished through the use of several different categories of alternatives, which are often described as the three 'Rs' of biomedical research. They are:

• Reduction

• Replacement

• Refinement

• Reduction Methods in Animal Testing

Researchers use techniques that allow them to obtain information that is sufficient but requires fewer animals. Conversely, researchers may be able to employ a method that allows them to obtain more information from the same number of animals. The end result is that fewer animals are used and therefore, fewer animals suffering .

• Types of Reduction Methods in Animal Testing

There are currently modified test methods that are essentially traditional models that have been advanced to provide comparable results with fewer animals. For example, newer versions of the Draize test can reduce the use of animals and additionally, can reduce the potential distress as well.

• Tissue cultures are also an extremely useful method for reducing the number

of animals used in laboratory experimentation.

• In addition, the use of computer models, databases and similar sources of

information can provide the history of a substance and its use as well as

offering preliminary information on the safety of a formula.

REPLACEMENT METHODS -

Replacement methods in animal testing involve actually replacing the use of

live animals with other methods that are completely non-animal in nature.

• Types of Replacement Methods in Animal Testing

• Whenever it is feasible, a replacement method such as an in vitro method is

performed in place of animal testing. In vitro methods refer to test tube

methods or cell cultures and these can be extremely valuable in replacing

animal models.

• Another way to replace animal use is to improve the use of information.

• This means that by using epidemiological studies and similar information, it may be possible to avoid animal testing in some instances. Using previously established information means that researchers can avoid repeating experiments.

• Also, mathematical and computer models be used

• Another method is the use of plants and microbes instead of animals.

• Human studies can sometimes completely substitute animal use in an experiment. In particular, human studies through the use of human volunteers have replaced animal testing for cosmetics development.

• Importance of Refinement Methods in Animal Testing

Refinement methods in animal testing are important because they aim to alleviate

pain and suffering in animals .The pain experienced by the animal can be caused

by tissue damage ,due to a surgical procedure, an injury or a specific disease.

The animal can also suffer from environmental stress or psychological stress as

well.

• Using Pharmaceuticals

• The use of anaesthetics, analgesics and pain-relievers can be helpful to relieving

pain or distress. Tranquilisers can also calm and relax the animal during an

experiment

• Using Technology

Technologies that are less invasive are also considered refinement techniques.

For instance, ultrasound and Magnetic Resonance Imaging (MRI) can both be

considered as refinement techniques.

• Reducing Psychological Distress

A distressed animal will not provide usable laboratory data so it is in the best

interest of the researcher to minimise pain for the animal's sake, while also

minimising pain in the interests of successful experimentation. Providing

animals with larger cages and toys can make a significant difference in the

animal's emotional well-being.

Making a Decision -

• Despite having a look at both sides involved in the controversy of animal

testing, there is still no clear right or wrong that seems to appease everyone.

One thing, however, appears to be unanimous - that at the very least, animal

suffering should be minimized and that animals should be respected during

their care. If animal testing is to continue - and at present it is ongoing -

animals must not be abused.

REFERENCES

• Background and History of Animal Testing Author: Ian

Murnaghan B.Sc (hons), M.Sc - Updated: 28 April 2015

• www.aboutanimaltesting.co.uk

• www.animalresearch.info

THANK YOU