[The role of group A5 catecholaminergic neurons in stress and morphine analgesia mechanisms in rats].

The activity of antinociceptive mechanisms in cold stress and under the effect of morphine was studied in experiments on rats subjected to bilateral destruction of group A5 neurons. In cold stress in rats of the experimental and control groups the latent periods (LP) of pain reactions of limb licking differed significantly, both in initial values and between the groups; in contrast, the LP of the tail-flick reaction did not differ significantly. Under the effect of morphine the pain reactions increased authentically as compared to the initial values both in the experimental and the control groups, but there were no significant differences between the groups. Thus, group A5 noradrenergic neurons have an effect on inhibiting some pain reaction components in cold stress, but are of no importance in the mechanisms of antinociceptive actions under the effect of morphine.