Intercostal and Cerebellar Influences on Efferent Phrenic Activity in the Decerebrate Cat

Abstract

The intercostal‐to‐phrenic reflex connections, previously studied only in spinal preparations, have now been further analyzed in decerebrate cats and rabbits. The early excitatory part of the response was of the same nature as the corresponcling response component in spinal preparations. The subsequent inhibitory phase was due both to post‐firing depression, as in the spinal state, and to active inhibition. The responses in decerebrate animals showed marked respiratory variations with almost complete abolishment of the excitatory component in the end‐expiratory phase. In the decerebrate preparation the responses from the different portions of the diaphragm showed qualitative differences which disappeared after spinalization. Further signs of differentiated intercostal‐to‐phrenic relations were obtained by stimulating different intercostal nerves. Stimulation of the anterior lobe of cerebellum exerted pronounced effects both on the respiratory phrenic activity–inhibition, sometimes followed by post‐tetanic facilitation–and on the intercostal‐to‐phrenic reflex–removing the inhibition in the end‐expiratory phase. Some of the features of the synaptic organization of the phrenic nucleus are discussed.

Olfactory Impairments in Patients with Unilateral Cerebellar Lesions Are Selective to Inputs from the Contralesional Nostril

“…Depression of cerebellar function in the cat by ischemia, topical administration of procaine, or ablation, results in an augmentation of inspiratory activity (Glasser et al, 1966). In addition, electrical stimulation of the anterior lobe of the cerebellum inhibits the inspiratory discharge driven by the medullary respiratory mechanism (Moruzzi, 1940;Decima and von Euler, 1969). Together, these results suggest that the cerebellum provides a tonic, primarily inhibitory, influence on inspiratory mechanisms of the lower brainstem.…”

“…Consistent with its role in respiration, the cerebellum may interact with either spinal inspiratory facilitatory reflexes or supraspinal inspiratory inhibitory reflexes to modify the diaphragm and intercostal muscles that control the sniff (Decima and von Euler, 1969). Depression of cerebellar function in the cat by ischemia, topical administration of procaine, or ablation, results in an augmentation of inspiratory activity (Glasser et al, 1966).…”

Extra‐segmental reflexes derived from intercostal afferents: phrenic and laryngeal responses

“…Caudal intercostal afferents cause phrenic excitation by a spinal reflex. (Decima & Euler, 1969b) and one in the anaesthetized animal (Remmers, 1970), explored the subject further, but left two questions unanswered:…”

Upper Thoracic Respiratory Interneurons Integrate Noxious Somatic and Visceral Information in Rats

“…Previous studies show that the respiratory movement pattern or phrenic nerve activity are reflexively changed by cutaneous and muscle afferents, which are processed at the spinal level and do not involve supraspinal sites (Decima and Von Euler 1969;Eldridge et al 1981;Koizumi et al 1961;Remmers 1970). TRINs receiving peripheral proprioreceptive and noxious somatic inputs could play a role in respiratory proprioreceptive reflexes and spinal processing of noxious information.…”

“…For example, electrical stimulation of the sympathetic afferents reflexively produces ipsilateral excitation and contralateral inhibition of the triangularis sterni (Coon et al 1995). Furthermore, stimulation of splanchnic afferents can activate phrenic motoneurons and change phrenic nerve discharges and respiratory activity in spinal cats (splanchnicphrenic reflex) (Albano and Garnier 1983;Decima and Von Euler 1969;Downman 1955). Modulation of TRINs by noxious cardiac inputs observed in the present study might provide a spinal mechanism for viscerorespiratory reflexes; however, the mechanism probably differs from the spinal neural hierarchy for the splanchnic-phrenic reflexes mentioned in the preceding text.…”