Cholinergic neurons in the pedunculopontine tegmental nucleus modulate breathing in rats by direct projections to the retrotrapezoid nucleus

Author(s)

Lima, Janayna D. ^[1] ; Sobrinho, Cleyton R. ^[1] ; Falquetto, Barbara ^[2] ; Santos, Leonardo K. ^[1] ; Takakura, Ana C. ^[2] ; Mulkey, Daniel K. ^[3] ; Moreira, Thiago S. ^[1]

Affiliation

^[1] Univ Sao Paulo, Dept Physiol & Biophys, Sao Paulo, SP - Brazil

^[2] Univ Sao Paulo, Dept Pharmacol, Sao Paulo, SP - Brazil

^[3] Univ Connecticut, Dept Physiol & Neurobiol, Storrs, CT 06269 - USA

• Document type: Journal article
• Source: JOURNAL OF PHYSIOLOGY-LONDON; v. 597, n. 7, p. 1919-1934, APR 2019.
• Web of Science Citations: 2

Abstract

Key points Cholinergic projections from the pedunculopontine tegmental nucleus (PPTg) to the retrotrapezoid nucleus (RTN) are considered to be important for sleep-wake state-dependent control of breathing. The RTN also receives cholinergic input from the postinspiratory complex. Stimulation of the PPTg increases respiratory output under control conditions but not when muscarinic receptors in the RTN are blocked. The data obtained in the present study support the possibility that arousal-dependent modulation of breathing involves recruitment of cholinergic projections from the PPTg to the RTN. The pedunculopontine tegmental nucleus (PPTg) in the mesopontine region has important physiological functions, including breathing control. The PPTg contains a variety of cell types, including cholinergic neurons that project to the rostral aspect of the ventrolateral medulla. In addition, cholinergic signalling in the retrotrapezoid nucleus (RTN), a region that contains neurons that regulate breathing in response to changes in CO2/H+, has been shown to activate chemosensitive neurons and increase inspiratory activity. The present study aimed to identify the source of cholinergic input to the RTN and determine whether cholinergic signalling in this region influences baseline breathing or the ventilatory response to CO2 in conscious male Wistar rats. Retrograde tracer Fluoro-Gold injected into the RTN labelled a subset of cholinergic PPTg neurons that presumably project directly to the chemosensitive region of the RTN. In unrestrained awake rats, unilateral injection of the glutamate (10 mm/100 nL) in the PPTg decreased tidal volume (V-T) but otherwise increased respiratory rate (f(R)) and net respiratory output as indicated by an increase in ventilation (V-E). All respiratory responses elicited by PPTg stimulation were blunted by prior injection of methyl-atropine (5 mm/50-75 nL) into the RTN. These results show that stimulation of the PPTg can increase respiratory activity in part by cholinergic activation of chemosensitive elements of the RTN. Based on previous evidence that cholinergic PPTg projections may simultaneously activate expiratory output from the pFRG, we speculate that cholinergic signalling at the level of RTN region could also be involved in breathing regulation. (AU)

• FAPESP's process: 15/23376-1 - Retrotrapezoid nucleus, respiratory chemosensitivity and breathing automaticity
• Grantee: Thiago dos Santos Moreira
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 16/23281-3 - Encephalic regions responsible for neuroplasticity observed in respiratory response induced by hypercapnia in a modelo of Parkinson's Disease
• Grantee: Ana Carolina Takakura Moreira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 15/12827-2 - Acetylcholine and ventilation: Modulation by cholinergic inputs from pedunculopontine tegmental nucleus to the retrotrapezoid nucleus
• Grantee: Cleyton Roberto Sobrinho
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 16/22069-0 - Amelioration of the brainstem vascular imbalances in an spontaneously hypertensive rats with exercise
• Grantee: Thiago dos Santos Moreira
• Support Opportunities: Regular Research Grants
• FAPESP's process: 17/01380-2 - Pedunculo pontine tegmental nucleus and brainstem respiratory interactions in breathing
• Grantee: Janayna Dias Lima
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)