Elsevier

Brain Research

Volume 491, Issue 2, 10 July 1989, Pages 243-252
Brain Research

Dorsal medullary inspiratory neurons: effects of superior laryngeal afferent stimulation

https://doi.org/10.1016/0006-8993(89)90060-7Get rights and content

Abstract

In decerebrate paralyzed cats ventilated with a cycle-triggered pump, we examined the responses of inspiratory (I) neurons in the region of the ventrolateral nucleus tractus solitarius (NTS) to single electrical stimuli delivered to the ipsilateral superior laryngeal nerve (SLN). Sixty-five I neurons were classified as: I(−), I(0), I(+,early), I(+,late) or I(other) on the basis of responses to lung inflation, and as I(bulbophrenic) or I(non-bulbophrenic) on the basis of evidence of an excitatory projection to the contralateral phrenic motoneuron pool. The peristimulus histograms of contralateral phrenic activity showed an early peak of excitation with average latency of4.9 ± 0.1ms(mean±S.E.M.), followed by depression at7.3 ± 0.2ms, start of recovery from depression at22.7 ± 1.0ms, and recovery to control levels at28.4 ± 1.1.ms. The peristimulus histograms of ipsilateral I unit activity showed an initial excitation (latency2.9 ± 0.3ms), followed by spiking silence (latency6.0 ± 0.6ms) and recovery to control discharge frequency at38.8 ± 3.6ms. This time of inhibition was significantly longer than the time of phrenic depression, suggesting that other bulbophrenic excitatory projections are able to rapidly compensate for decreased NTS output. Subgroups of I neurons, as classified by lung inflation tests, did not differe significantly with respect to these timing variables. In contrast, latencies of excitation for I(bulbophrenic) neurons were significantly less than for I(non-bulbophrenic) neurons.

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    *

    Present address: Pediatric Pulmonary Division, Columbia Presbyterian Medical Center, New York, NY 10032, U.S.A.

    **

    Present address: Research Center, Schneider Children's Hospital, Long Island Jewish-Hillside Medical Center, New Hyde Park, NY 11042, U.S.A.

    **

    Present address: Department of Physiology, Shandong Medical University, Jinan, Shandong, People's Republic of China.

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