THE MORPHOLOGY AND CONNECTIONS OF NEURONS IN THE GASPING CENTER OF ADULT-RATS

Neuronal activities in the intermediate reticular nucleus and adjacent lateral tegmental held are critical for the neurogenesis of the venti latory pattern of gasping. We report herein the anatomical features of these neurons, their axonal projections and the location of neurons p roviding afferent inputs. These neuroanatomical evaluations were perfo rmed by iontophoretic injection of the tracer Neurobiotin(TM) into the region of the intermediate reticular nucleus of the rat. At the site of injection, neurons having soma of 30-50 mu m were filled. Labelled axons and terminals were observed in ipsilateral regions which contain neurons having established functions in the control of ventilatory ac tivity. These regions include the nucleus ambiguus and motor nuclei of the hypoglossal and facial nerves. In addition, axonal projections ex tended to the contralateral region of the intermediate reticular nucle us. From this contralateral region, retrograde tracing revealed projec tions to the site of injection. Similarly, many ipsilateral regions wh ich received axonal terminals from the region of the intermediate reti cular nucleus had reciprocal projections to this region. These anatomi cal results support the physiological observation that the neurogenesi s of gasping involves a synchronized activation of diverse components of the brainstem ventilatory control system. Copyright (C) 1996 IBRO. Published by Elsevier Science Ltd.