Respiratory muscle responses elicited by dorsal periaqueductal gray stimulation in rats

Abstract

The periaqueductal gray matter is an essential neural substrate for central integration of defense behavior and accompanied autonomic responses. The dorsal half of the periaqueductal gray matter (dPAG) is also involved in mediating emotional responses of anxiety and fear, psychological states that often are associated with changes in ventilation. However, information regarding respiratory modulation elicited from this structure is limited. The present study was undertaken to investigate the relationship between stimulus frequency and magnitude on ventilatory pattern and respiratory muscle activity in urethane-anesthetized, spontaneously breathing rats. Electrical stimulation in the dPAG-recruited abdominal muscle activity increased ventilation and increased respiratory frequency by significantly shortening both inspiratory time and expiratory time. Ventilation increased within the first breath after the onset of stimulation, and the respiratory response increased with increasing stimulus frequency and magnitude. dPAG stimulation also increased baseline EMG activity in the diaphragm and recruited baseline external abdominal oblique EMG activity, normally quiescent during eupneic breathing. Significant changes in cardiorespiratory function were only evoked by stimulus intensities >10 microA and when stimulus frequencies were >10 Hz. Respiratory activity of both the diaphragm and abdominal muscles remained elevated for a minimum of 60 s after cessation of stimulation. These results demonstrate that there is a short-latency respiratory response elicited from the dPAG stimulation, which includes both inspiratory and expiratory muscles. The changes in respiratory timing suggest rapid onset and sustained poststimulus dPAG modulation of the brain stem respiratory network that includes expiratory muscle recruitment.

Periaqueductal gray matter modulates the hypercapnic ventilatory response

“…Electrical or chemical stimulation of the dPAG is known to evoke significant increases in blood pressure and HR [3,6,14,21,43,73]. In contrast, vPAG stimulation induces depressant effects, such as lowered blood pressure and HR, coupled with immobility [3,6,14].…”

The Midbrain Periaqueductal Gray Control of Respiration

“…Moreover, none of these studies explores stereotaxically the influence of different areas of the PAG on respiratory function. Subramanian et al (2007Subramanian et al ( , 2008 studied the PAG-induced changes to caudal medullary respiration-related neuronal activity in the rat, and Huang et al (2000) also in the rat investigated the role of the PAG on cardiorespiratory control, and subsequently Hayward et al (2003Hayward et al ( , 2004 and Zhang et al (2005Zhang et al ( , 2007 examined the PAGinduced change to respiratory frequency. However, all these studies in the rat focused on the dorsal PAG and reported only excitatory effects.…”

“…In these studies (Magoun et al, 1937;Bandler and Carrive, 1988;Zhang et al, 1994;Nonaka et al, 1999;Nakazawa et al, 2000), the sound production was measured but not the respiratory function. In the rat, a few studies exist (Huang et al, 2000;Hayward et al, 2003Hayward et al, , 2004Zhang et al, 2005Zhang et al, , 2007Subramanian et al, 2007Subramanian et al, , 2008, but they were limited to the dorsal PAG showing only an increase in respiratory frequency. The present study is the first that investigated the PAG effects on respiration by stimulation of different parts of the PAG.…”

Respiratory manifestations of panic disorder in animals and humans: A unique opportunity to understand how supramedullary structures regulate breathing

“…Under "resting" conditions (i.e. normoxic-normocapnia) electrical and chemical stimulation of dorsal PAG (dPAG) increase ventilation in both cats and rats (Bassal and Bianchi, 1982;Duffin and Hockman, 1972;Hayward and Castellanos, 2004;Hayward et al, 2003;Hockman et al, 1974;Huang et al, 2000;Lovick, 1985;Zhang et al, 2005). However, the recent demonstration that focal lesions in the dlPAG/dmPAG does not alter ventilation during normocapnia, suggests that this area does not exert a tonic influence on respiratory control at rest but may be activated in specific situations (Lopes et al, 2012).…”