SUPPRESSION OF PONTOGENICULOOCCIPITAL WAVES BY NEUROTOXIC LESIONS OF PONTINE CAUDO-LATERAL PERIBRACHIAL CELLS

Ponto-geniculo-occipital waves precede rapid eye movement sleep and pl ay an important role in triggering and maintaining rapid eye movement sleep. Ponto-geniculo-occipital waves have been implicated in several important functions such as sensorimotor integration, learning, cognit ion, development of the visual system, visual hallucination, and start le response. Peribrachial area neurons have long been thought to play a key role in the triggering of ponto-geniculo-occipital wave. However , the exact location within the peribrachial area for triggering ponti ne ponto-geniculo-occipital wave has not been unequivocally demonstrat ed. In an attempt to address this issue, kainic acid was microinjected (1.0 mu g) unilaterally into the caudo-lateral peribrachial area of f our cats in order to destroy the cell bodies located In that region an d thus to study the effects of the destruction upon waking-sleep state s and ponto-geniculo-occipital waves. The kainic acid produced a small spherical area of nerve cell loss and/or gliosis centered on the ster eotaxic coordinates of P: 4.0, L: 4.5, and H: -2.5. The maximum diamet er of that spherical area of cell loss was 0.9 mm. Unilateral lesionin g of the caudo-lateral peribrachial area decreased ponto-geniculo-occi pital waves during rapid eye movement sleep by 85% ipsi-laterally and 15% contralaterally in the lateral geniculate body without significant ly changing the amounts of time spent in wake, slow-wave sleep, and ra pid eye movement sleep. These results suggest that the caudo-lateral p eribrachial area cells are critical to the genesis of ponto-geniculo-o ccipital waves, and provide compelling evidence that the different par ts of the peribrachial area have quite different roles in the generati on of discrete rapid eye movement sleep signs. We propose that caudo-l ateral peribrachial cells exert an excitatory influence on rostral per ibrachial cells, which then directly activate the ponto-geniculo-occip ital waves that are recorded in the lateral geniculate body. Results o f this study are not only important to understand the mechanisms gener ating ponto-geniculo-occipital waves but also could be used as an expe rimental tool to study the functions of this wave.