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We studied the analgesic effect of olipiphate, a product of lignin, against writhing provoked by intraperitoneal injection of acetic acid. Paracetamol was used as the reference drug. Both agents dose-dependently decreased the number of motor reactions caused by the irritant. Olipiphate possessed analgesic activity and efficiency comparable with those of paracetamol, but produced a more long-lasting effect.

Male Wistar rats with a silicone cannula implanted into a jugular vein were each placed, for 6 h daily on 5 successive days, in a standard Skinner box where they were trained to self-administer morphine intravenously by pressing a bar. Kynurenic acid, an endogenous nonselective antagonist of excitatory amino acids, injected into rats before their placement in the Skinner box inhibited in a dose-dependent manner the acquisition by them of the morphone self-administration habit, as assessed by the number of times the bar was pressed.

The effect of excitatory amino acid receptor antagonists on the development of the conditioned reflex component of the tolerance for morphine analgesia is studied. It is demonstrated that the antagonists of NMDA and non NMDA receptors reduce the development of associated component of the tolerance, while the magnitude of the nonassociative component changes after co-administration of morphine with NMDA receptor antagonists.

Rats with lateral hypothalamic self-stimulation (SS) were given morphine injections twice a day for 15 days in doses rising from 20 to 120 mg/kg. Morphine facilitated SS starting with the 9th injection. Short-term (16–18 h) withdrawal of the narcotic from the rats or its discontinuation led to inhibition of SS. Complete suppression of SS was observed after injection of the morphine antagonist nalorphine in a dose of 5 mg/kg.

Naloxone (5 mg/kg, subcutaneously) had no significant effect on the electrical self-stimulation response in rats with electrodes in the lateral hypothalamus. An analgesic effect of stimulation of the “reward” zones was found in three animals, in the form of raising of the threshold of pain vocalization during electrical stimulation of the tail. The antinociceptive action was abolished by naloxone. Morphine (3 mg/kg) activated the self-stimulation response, whereas naloxone antagonized this action. The role of opiate receptors in self-stimulation effects and in central analgesia is discussed.

The fatty acid composition of the total lipids of the myocardium, lungs, liver, intestine, adipose tissue, and blood plasma was investigated in the course of development of traumatic shock produced in dogs by crushing the soft tissues of the thigh. The development of shock is accompanied by an increase in the relative percentage of linoleic and arachidonic acids in the blood plasma and certain organs; close correlation was found between the linoleic acid concentrations in the adipose tissue and blood. A deficiency of oleic acid also was observed in the lipids of the organs studied.