Distribution of [3H]colchicine in brain and spinal cord areas following its intracerebroventricular or intra-spinal cord injection in rats.

Intracerebroventricular or intra-spinal cord (at lumbar level) injection of low doses of colchicine leads to irreversible urine retention. To learn whether colchicine induces this effect by diffusing from the sites of injection, we studied, using the above-mentioned routes of administration, the distribution of [3H]colchicine in brain and spinal cord areas as a function of time. The release of [3H]colchicine into the blood and its elimination via the renal route was studied as well. The results of these experiments show that after its intracerebroventricular injection, [3H]colchicine diffuses to brain areas that normally exert a facilitatory or inhibitory action on urine excretion but reaches the lumbar region in only modest amounts (0.02%). On the other hand, after its intra-spinal cord injection, [3H]colchicine remains at the site of injection, where the sacral micturition center is located. This suggests that intracerebroventricular or intra-spinal cord injected colchicine induces urine retention by exerting its action at two different levels of the neuronal pathway that regulates micturition, depending on the site of injection.