EFFECTS OF CHOLECYSTOKININ ON Y-CELLS, X-CELLS, AND W-CELLS IN THE DORSAL LATERAL GENICULATE-NUCLEUS OF RATS

The role of the cholecystokinergic input to the rat's dorsal lateral g eniculate nucleus (dLGN) was studied by examining the effect of iontop horetically administered CCK-8S on the neuronal response to stimulatio n of the receptive field center. Peristimulus activity was recorded ex tracellularly from 108 neurons grouped according to the type of recept ive field (OFF ON, or ON-OFF) and classified with respect to their Y, X, or W properties by means of discriminant analysis. CCK affected the response to a center-sized spot of light in two thirds of tile neuron s investigated. The center response decreased in 50 of 73 CCK-sensitiv e neurons (69%), predominantly in Y OFF and X OFF center cells (17 of 19). In the remaining 23 cells the center response increased. most con sistently (11 of 17) in W ON center cells. Center and surround respons es were similarly influenced. Inhibitions and excitations induced by C CK-8S were reproducible, dose dependent, and receptor mediated. The CC KB antagonist PD 135158 reduced the CCK effects in 10 of 14 cells; the CCKA antagonist KL 1001 reduced the CCK effects in 17 of 36 cells. Th e CCK-induced inhibition was B-receptor specific in 4 of 8 cells, A-re ceptor specific in 2 of 8 cells, and partially mediated by each of the two types of receptor in the remaining 2 cells. Blocking by the CCKA antagonist was more frequently observed in W cells than in cells with Y or X characteristics. The data show that CCK modifies the activity o f dLGN cells in a variable direction depending on the specific cell ty pe (Y, X, W) and response pattern (OFF ON). The effects of CCK are dis cussed in relation to proposed functions of the superior collicular in put to the dLGN.