Effect of morphine on leucocyte kinetics. II. Effect of morphine on the white blood count of rabbits' peripheral blood following atropine induced blockade of the parasympathicus and in epinephrectomized animals.

Acute administration of morphine provokes rapid changes in the white blood count of the peripheral blood, initial leucopenia in the differential blood count characterized by both relative and absolute lymphopenia, the PMN level remaining unchanged. The initial leucopenia gradually turns into leucocytosis, the lymphocyte level remaining still low and PMN multiplicating massively. The PMN multiplication is taking effect primarily through their shift from the marginal to the circulation pools. Morphine can be prevented from acting upon the white blood count either by epinephrectomy or naloxon premedication. Our conclusion is that the morphine effect on the white blood count is due to the activation of the hypophysis-adrenal cortex axis mediated by specific receptors.