[Effect of dopaminergic substances on the antinocifensive action of arecoline].

Based on earlier studies that revealed the analogical influence of noradrenaline and serotonin on morphine analgesia and the antinocifensive effect of arecoline, it was tested whether under the influence of dopaminergic substances the inhibition of nocifensive reactions is being altered by arecoline like the action of morphine. In fact, arecoline could be amplified in a dose dependent manner by apomorphine and amphetamine, which alone had no antinocifensive effects. On the other hand, no antagnoism of the dopamine receptor blockers, chloropromazine ahd haloperidole, against arecoline was demonstrable; only the additive effect of apomorphine and amphetamine could be abolished. Therefore it is concluded that dopamine is not directly involved in the spinal mechanism of the antinocifensive effect of central cholinomimetics, but that only supraspinal influences can be varied by the function of dopaminergic neurons.