Responses of Brainstem Respiratory Neurons to Activation of Midbrain Periaqueductal Gray in the Rat

Eupneic breathing has been shown to be affected by output from the midbrain periaqueductal gray matter (PAG) (Huang et al. 2000; Hayward et al. 2003; Subramanian et al. 2007). In the rat, anatomical tracing studies have demonstrated connections between the PAG and other brainstem areas. It is generally accepted that PAG efferents activate descending pathways that originate in the medulla (Holstege 1991b). The aims of our studies were to isolate and record from respiratory cells in the ventral respiratory group (VRG) and the nucleus tractus solitarius (NTS) regions of the rat brainstem and to examine the changes in firing patterns and timing of these cells following excitatory amino acid (EAA) stimulation of the PAG. We also investigated the effect of β-adrenergic blockade in the vlNTS on the PAG induced respiratory patterning.