Nociceptive reactions during stimulation of immunity in rats with various individual resistance to stress

: Various behavioural nociceptive reactions and individual resistance against stress were studied under conditions of stimulation of the immune processes by various techniques. The research problems included a study of influence of the immune stimulation with preparation "Imunofan" upon pain responses depending on individual resistance of animals to a stress, and the obtained results were compared with similar data in natural model of immune activation. To reveal central immune regulation of nociceptive reactions, imunofan was injected into brain ventricles. The work was carried out in 43 "Wistar" adult male rats. Free "open field" behaviour of animals was recorded to define a stress-resistance. Following nociceptive reactions, tail-flick to thermal stimuli; start, escape, jumping and vocalization to electrical skin stimulation, were studied. It was shown that intramuscular injection of imunofan (0.01 ml, 0.005% solution) depressed an active behaviour of animals in open field and reduced pain thresholds. This hyperalgesia was much higher in non-resistant rats in comparison to the resistant ones. Similar results were obtained in natural activation of immunity caused by operative procedure necessary for injection of imunofan into ventricles. Intracerebroventricular injections were accompanied by stronger and more complex changes of pain sensitivity.