Control of breathing and blood pressure by parafacial neurons in conscious rats

Author(s)

Takakura, Ana C. ^[1] ; Moreira, Thiago S. ^[2] ; De Paula, Patricia M. ^[3] ; Menani, Jose V. ^[3] ; Colombari, Eduardo ^[3]

Affiliation

^[1] Univ Sao Paulo, Inst Biomed Sci, Dept Pharmacol, BR-05508900 Sao Paulo - Brazil

^[2] Univ Sao Paulo, Inst Biomed Sci, Dept Physiol & Biophys, BR-05508900 Sao Paulo - Brazil

^[3] Sao Paulo State Univ UNESP, Sch Dent, Dept Physiol & Pathol, BR-14801903 Araraquara, SP - Brazil

• Document type: Journal article
• Source: Experimental Physiology; v. 98, n. 1, p. 304-315, JAN 2013.
• Web of Science Citations: 13

Abstract

The retrotrapezoid nucleus (RTN), located in the parafacial region, contains glutamatergic neurons that express the transcriptor factor Phox2b and that are suggested to be central respiratory chemoreceptors. Studies in anaesthetized animals or in vitro have suggested that RTN neurons are important in the control of breathing by influencing respiratory rate, inspiratory amplitude and active expiration. However, the contribution of these neurons to cardiorespiratory control in conscious rats is not clear. Male Holtzman rats (280-300 g, n = 6-8) with bilateral stainless-steel cannulae implanted into the RTN were used. In conscious rats, the microinjection of the ionotropic glutamatergic agonist NMDA (5 pmol in 50 nl) into the RTN increased respiratory frequency (by 42%), tidal volume (by 21%), ventilation (by 68%), peak expiratory flow (by 24%) and mean arterial pressure (MAP, increased by 16 +/- 4, versus saline, 3 +/- 2 mmHg). Bilateral inhibition of the RTN neurons with the GABA(A) agonist muscimol (100 pmol in 50 nl) reduced resting ventilation (52 +/- 34, versus saline, 250 +/- 56 ml min(-1) kg(-1) with absolute values) and attenuated the respiratory response to hypercapnia and hypoxia. Muscimol injected into the RTN slightly reduced resting MAP (decreased by 13 +/- 7, versus saline, increased by 3 +/- 2 mmHg), without changing the effects of hypercapnia or hypoxia on MAP and heart rate. The results suggest that RTN neurons activate facilitatory mechanisms important to the control of ventilation in resting, hypoxic or hypercapnic conditions in conscious rats. (AU)

• FAPESP's process: 09/54888-7 - Neural mechanisms involved on chemoreception
• Grantee: Eduardo Colombari
• Support type: Research Projects - Thematic Grants
• FAPESP's process: 10/09776-3 - Neural mechanisms involved in expiratory rhythm generator: possible involvement of the retrotrapezoid nucleus and the parafacial region
• Grantee: Ana Carolina Thomaz Takakura
• Support type: Research Grants - Young Investigators Grants
• FAPESP's process: 10/19336-0 - Pontine mechanisms involved in cardiorespiratory control during central or peripheral chemoreceptors activation
• Grantee: Thiago dos Santos Moreira
• Support type: Regular Research Grants