Morphine-like analgesics and convulsive threshold for pentetrazole in dogs

In dogs, the influence of morphine (1 mg/kg i.m.), fentanyl (10 and 30 micrograms/kg i.v.), meperidine (6 mg/kg i.m.), and pentazocine (3 mg/kg i.m.) on the pentetrazole seizure threshold was studied. Pentetrazole was infused i.v. at a rate of 10 mg/kg per min up to the first generalized myoclonic jerk. The analgesic treatments lowered the seizure threshold considerably in 5 out of 6 dogs, and fentanyl and pentazocine led to an increased incidence of clonic-tonic seizures after the end of the pentetrazole infusion.