Descending control of the respiratory neuronal network by the midbrain periaqueductal grey in the rat in vivo
Article first published online: 10 DEC 2012
© 2012 The Author. The Journal of Physiology © 2012 The Physiological Society
The Journal of Physiology
Volume 591, Issue 1, pages 109–122, January 2013
How to Cite
Subramanian, H. H. (2013), Descending control of the respiratory neuronal network by the midbrain periaqueductal grey in the rat in vivo. The Journal of Physiology, 591: 109–122. doi: 10.1113/jphysiol.2012.245217
- Issue published online: 7 JAN 2013
- Article first published online: 10 DEC 2012
- Accepted manuscript online: 7 NOV 2012 08:23PM EST
- (Resubmitted 19 September 2012; accepted after revision 30 October 2012; first published online 5 November 2012)
- • Basic respiratory rhythm is generated and maintained by neurones located in the medulla oblongata.
- • This basic respiratory rhythm is changed by neurones in the region called the periaqueductal grey (PAG) located in the midbrain, in order to modulate breathing for behaviour and emotional expressivity.
- • How the PAG converts basic respiratory rhythm into behavioural breathing is not known.
- • In this study I investigated the influence of the PAG on two important populations of medullary neurones, the late-inspiratory (late-I) and post-inspiratory (post-I) neurones, which are thought to be involved in mediating rhythmic inspiration to expiration phase transition.
- • I show that the PAG modulates the activity of the medullary late-I and post-I neurones, and this modulation contributes to the conversion of basic breathing into behavioural breathing.
Abstract Emotional reactions such as vocalization take place during expiration, and thus expression of emotional behaviour requires a switch from inspiration to expiration. I investigated how the midbrain periaqueductal grey (PAG), a known behavioural modulator of breathing, influences the inspiratory-to-expiratory phase transition. Contemporary models propose that late inspiratory (late-I) and post-inspiratory (post-I) neurones found in the medulla, which are active during the inspiratory-to-expiratory phase transition are involved in converting inspiration to expiration. I examined the effect of excitatory amino acid (d,l-homocysteic acid; DLH) stimulation of the PAG on the discharge function of late-I and post-I neurones. The data show a topographical organization of DLH-induced late-I and post-I neuronal modulation within the PAG. Dorsal PAG stimulation induced tachypnoea and caused excitation of both the late-I and post-I neurones. Lateral PAG induced inspiratory prolongation and caused an excitation of late-I neurones but inhibition of post-I neurones. Ventrolateral PAG induced expiratory prolongation and caused a persistent activation of post-I neurones. As well, PAG stimulation modulated both the late-I and post-I cells for least two–three breaths even prior to the change in respiratory motor pattern. This indicates that the PAG influences the late-I and post-I cells independent of pulmonary or other sensory afferent feedback. I conclude that the PAG modulates the activity of the medullary late-I and post-I neurones, and this modulation contributes to the conversion of eupnoea into a behavioural breathing pattern.