Effects on body temperature of prostaglandins of the A, E and F series on injection into the third ventricle of unanaesthetized cats and rabbits

Abstract

1. Prostaglandins were injected into the third ventricle of unanaesthetized cats and rabbits whilst rectal temperature was recorded. 2. In cats prostaglandin E 1 and E 2 (PGE 1 and PGE 2) produced hyperthermia which mostly began within a minute of injection and lasted 1 or more hours. With PGE 1 the hyperthermia was shown to be dose dependent between 10 ng and 10 μg (2·8 × 10 μ11 and 2·8 × 10−8 M). The hyperthermia was associated with vigorous shivering, skin vasoconstriction and piloerection. In several experiments a secondary rise in temperature occurred a few hours after the injection but such an effect was sometimes observed with control injections of 0·9% NaCl solution as well. 3. None of the other prostaglandins (A 1, F 1α, F 2α) examined in cats had an immediate or strong effect on temperature comparable to the hyperthermia produced by PGE 1 and PGE 2. 4. In rabbits PGE 1 (2 μg) also caused hyperthermia which began shortly after the injection and lasted for hours. PGF 2α and PGA 1, did not affect temperature. 5. In cats it was seen that an intraperitoneal injection of 4‐acetamidophenol (paracetamol 50 mg/kg) did not affect the initial strong hyperthermia produced by PGE 1 and PGE 2 but abolished the secondary rise. 6. The possibility is discussed that PGE 1 plays a role as a central transmitter or modulator in temperature regulation.