Recurrent Inhibitory Interneurons of the Rabbit's Lateral Posterior-
Pulvinar Complex.
J. Julius Zhu and Fu-Sun Lo.
Shanghai Brain Research Institute, Chinese Academy of Sciences, 320 Yue-
Yang Road, Shanghai 200031, People's Republic of China.
APStracts 4:173N, 1997.
ABSTRACT
We recorded from 118 neurons in the visual sector of the thalamic reticular
nucleus (TRN) in anesthetized rabbits. Cells were identified by their location
and characteristic burst responses to stimulation of the primary visual cortex
(Cx) and optic chiasm (OX), and were classified into two groups. Type I cells
had relatively short latencies from both OX and Cx stimulation, and the
latency from OX was always longer than from Cx. In contrast, type II cells had
much longer latencies following OX and Cx stimulation, and the latency from OX
was always shorter than from Cx. Type I cells were located in the dorsal part
of TRN, while type II cells, in the ventral part of TRN. The physiological
properties and location of type I TRN cells indicate that they are recurrent
inhibitory interneurons of the dorsal lateral geniculate nucleus (LGN). Type
II TRN cells most likely function as recurrent inhibitory interneurons for the
lateral posterior nucleus-pulvinar complex (LP), since they could be
antidromically activated by LP stimulation and orthodromically activated via
axonal collaterals of LP cells. Type II TRN cells exhibited a prolonged
depression after Cx or OX stimulation. Intracellular recordings showed that a
prolonged inhibitory postsynaptic potential (IPSP) was evoked by Cx or OX
stimulation. Therefore, these recurrent interneurons of LP, type II cells,
form mutual inhibitory connections, just like those recurrent interneurons of
LGN, type I cells. Our data suggest that the geniculocortical and
extrageniculate visual pathways have similar recurrent inhibitory circuits.
Received 15 April 1997; accepted in final form 24 July 1997.
APS Manuscript Number J307-7.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 28 August 1997