U-73122

U-73122 is a phospholipase C (PLC) and 5-LO (5-lipoxygenase) inhibitor with an IC₅₀of 1-2.1 µM for PLC. In Vitro: U-73122 potently inhibits receptor-coupled activation of PLC in membranes isolated from PMNs^[1]. U-73122 inhibits N-formyl-methionyl-leucyl-phenylalanine-induced aggregation of human polymorphonuclear neutrophils (PMN) and the associated production of IP₃ and diacyglycerol^[2]. U-73122 markedly inhibits inositol phosphate release elicited by either oxotremorine-M or guanosine-5'-O-(3-thiotriphosphate) than that induced by added Ca²⁺ in digitonin-permeabilized cells^[3]. In Vivo: U73122 significantly attenuates TNF-α mRNA expression, has no effect on sham animals, but significantly increases heart work and rate of contraction and relaxation without affecting heart rate in endotoxemic mice^[4]. U73122 (400 nM/μL) significantly reduces total lordosis durations, compared to vehicle infusions to the VTA, of oestradiol and progesterone-primed hamsters. VTA infusions of U73122 do not alter motor behaviour of hamsters in the activity monitor, but there is a significant effect of muscimol to decrease total number of beam breaks compared to hamsters administered SKF38393^[5].