Differential effects of colchicine on central dopaminergic neuronal activity and prolactin secretion in estrogen-primed ovariectomized rats

Colchicine is a potent chemical that disrupts the assembly of microtubulin and affects the integrity of cytoskeleton. It is commonly used to block the axonal transport in neurons. Central administration of colchicine (48 microg/3 microl/rat) two days earlier significantly lowered 3,4-dihydroxyphenylacetic acid (DOPAC) levels in the striatum and nucleus accumbens, both in the morning and in the afternoon. Median eminence DOPAC levels exhibit a diurnal change between morning and afternoon as previously shown. Colchicine treatment lowered and elevated median eminence DOPAC levels in the morning and afternoon, respectively. The estrogen-induced prolactin surge was also blocked. The findings indicate that neuronal inputs are necessary for maintaining basal activities in all dopaminergic neurons, while an inhibitory one predominates in the afternoon for TIDA neurons.