Optokinetic response of cells in the nucleus reticularis tegmenti pontis of the pigmented rabbit.

In immobilized pigmented rabbits anesthetized with N2O (70%) and halothane (2-4%), extracellular spikes were recorded from neurons in the nucleus reticularis tegmenti pontks (NRTP) and their responses to optokinetic stimulation (OKS) were examined. OKS was delivered using constant-velocity (0.1-4.0 degrees/s) movements of a random dot pattern (60 degrees x 60 degrees) at 0 degree, 45 degrees, 90 degrees or 135 degrees to the horizon. With OKS delivered to the contralateral eye (n = 43), the preferred directions of NRTP cells were forward (F, n = 10), backward (B, n = 7), downward (D, n = 5), and the remaining cells showed no response (N, n = 21). With OKS delivered to the ipsilateral eye (n = 43), the preferred directions were F (n = 8), B (n = 8), upward (U, n = 2), D (n = 1) and N (n = 24). The majority of cells which responded to OKS (17/22 for contralateral, and 16/19 for ipsilateral OKS) preferred the horizontal orientation. The optimum velocity ranged from 0.2 to 1 degree/s. The results suggest that the NRTP cells mainly transfer horizontal optikinetic signals to the flocculus and control horizontal optokinetic eye movements.