WAG/Rij rats: a strain of rat which are descendents of an inbred strain originated by AL Bacharach in 1924 from outbred Wistar Institute stock. WAG/Rij rats have inborn generalized absence epilepsy used in the study of epilepsy.

Waksman, Selman A (1888-1973): a Russian-born microbiologist who won the 1952 Nobel Prize for Physiology or Medicine "for his discovery of streptomycin, the first antibiotic effective against tuberculosis".
http://nobelprize.org/nobel_prizes/medicine/laureates/1952/waksman-bio.html

Wallerian degeneration: axonal and myelin degeneration observed in nerves and named after Augustus Waller.

Warfarin: a coumarin-type oral anticoagulant and inhibitor of the synthesis of vitamin K-dependent clotting factors, ie factors II, VII, IX and X. Despite its use in the past as a rat poison, warfarin is used clinically to treat prophylaxis of embolisation in rheumatic heart disease and atrial fibrillation and for the prevention of venous thrombosis of various causes. It is also used in cats that survive acute thromboembolism. Warfarin is referred to as an indirect anticoagulant and acts only in vivo by inhibiting the post-translational g-carboxylation of glutamic acid residues in clotting factors II, VII, IX and X (catalyzed by a vitamin K-dependent carboxylase). It inhibits the reduction of vitamin K.

Washout period: a short period of time in which drug treatment is withdrawn before a second treatment is given. Washout periods are used because the effects of small, residual concentrations of the first drug may affect the actions of the second drug.

WAT: white adipose tissue

Watanabe heritable hyperlipidemic rabbit (WHHL): a strain of rabbit with continuously inherited hyperlipidaemia produced originally by inbreeding from a mutant discovered in 1973 by Y. Watanabe. These rabbits show abnormally increased serum levels of cholesterol and triglyceride at various ages of approximately 8 to14-fold in comparison with control levels in normal Japanese white rabbits. In addition, spontaneous development of aortic atherosclerosis over about 6 months of age is common. These animals are commonly used in investigations of familial hypercholesterolaemia and in studies of antihypercholesterolemics and antihyperlipidemics.

WB4101: a selective α_1A-adrenoceptor antagonist.

W/BF1 mice: mice which exhibit disorders in systemic autoimmunity including thrombocytopenia, lupus nephritis, and coronary vascular disease and myocardial infarction. They have been used as animal models of autoimmune disease.

WBN/kob: an animal model of diabetes mellitus.

Wet dog shake: a type of behaviour observed in dogs and rodents in which they shake their bodies as if the fur was wet. It can be induced by 5-hydroxytryptophan and inhibited in rats by selective 5-HT₂ receptor antagonists such as ketanserin, pirenperone and methysergide. This type of behaviour has been used as a non-invasive means to study drugs affecting 5-HT₂ receptors in vivo.
Yap CY, Taylor DA. Involvement of 5-HT₂ receptors in the wet-dog shake behaviour induced by 5-hydroxytryptophan in the rat. Neuropharmacology (1983) 22:801-804

WHHL: Watanabe heritable hyperlipidemic rabbit

White adipose tissue (WAT): a fat storage tissue which secretes a number of peptide hormones such as leptins, cytokines, adipsin, angiotensinogen, adiponectin and resistin. It also produces steroids hormones.

WIC-Hyd rat: a mutant rat developed from the Csk: Wistar-Imamichi rat which shows spontaneous hydrocephalus.

Wistar rat: originally from the Wistar Institute, this commonly used albino rat which shows a low incidence of hydronephrosis.

Wistar-Kyoto (WKY) rats: rats derived from outbred Wistar rats at Kyoto School of Medicine in Japan in the early 1970s. This strain has been continuously inbred as a normotensive control strain for spontaneously hypertensive rats although these two strains differ at certain genetic loci. This albino strain is commonly used in evaluating compounds that exert effects of the cardiovascular system.

Withanolides: a group of about 50 pharmacologically active compounds present in roots and leaves of a plant known as Ashwagandha (Withania somnifera, also known as Indian ginseng and a plant used in Ayurvedic and alternative medicine). Witaholides are similar to ginsenosides and contain, for example, withaferol A has bacteriostatic and anticancer effects. See www.withanolide.com.

Withholding periods: periods of time in which certain drugs should not be administered to animals if their milk or meat is intended for human consumption. This period of time is measured from the day of final drug dosing to slaughter. The withholding period varies between drugs but is, for example, 7-14 days for oxyclozanide (used to treat flukes in cattle) and 21-30 days for closantel (also used to treat fluke infections). The periods for milk consumption are usually shorter at 3-5 days. This period of time is closely related to drug excretion rates and protein binding.

WKY rast: Wistar-Kyoto rats

Wobbler mouse: a mouse model of progressive degeneration of motoneurons which leads to atrophy of skeletal muscles. This is due to a recessive wobbler mutation on chromosome 11.

Worcester rat: the Bio-breeding/Worcester rat is an animal model autoimmune disbetes mellitus.

Wortmannin: a potent, selective and irreversible inhibitor of phosphatidylinositol 3-kinase, mitogen-activated protein kinase and myosin light chain kinase which is obtained from Penicillium fumiculosum. See wortmannin.4mg.com.

Wrap restraint stress:  an animal model of irritable bowel syndrome. Restraining an animal such as a rat by wrapping it to restrain it causes an increase in fecal pellet production. This model has been used to test the effects of anxiolytics.
Williams C L et al. Stress-induced changes in intestinal transit in the rat: A model for irritable bowel syndrome. Gastroenterology (1988) 94:611-621

Writhing: acetic acid writhing assay