Bilateral ablation of frontal cortex reduces concentration of cholecystokinin-like immunoreactivity in rat dorsolateral striatum.

Rat striatum (caudatoputamen, CP) contains high concentrations of cholecystokinin-like immunoreactivity (CCK-LI) which is not synthesized in the CP itself, but is brought to it by afferent projections. Some of these have been reported to originate in the sensori-motor cortex. The source of the major part of the CCK-LI in the CP is not known. In the present study, it was investigated whether neurons in the frontal cortex send CCK-LI-containing fibers to the CP. Ablation of the frontal pole of one hemisphere did not decrease but significantly enhanced the CCK-LI in the dorsal CP. Unilateral ablation of the frontal pole combined with the ipsilateral severance of corpus callosum fibers reduced ipsilaterally the concentration of CCK-LI in the dorsolateral CP by approximately 60%. Also ablation of the frontal poles of both sides bilaterally reduced the concentration of CCK-LI in the dorsolateral CP by approximately 40%. It is concluded that the neuronal elements in the dorsolateral CP of one side, which contain CCK-LI, are in some way connected with neurons in the frontal poles of both hemispheres. This connection may be just functional or may be due to CCK-containing fibers, which originate in the frontal pole.