Home  About us  Contact
 

Ventral Respiratory Group (ventral + respiratory_group)

Distribution by Scientific Domains
Life Sciences75%

Selected Abstracts

Astrocytic calcium signals induced by neuromodulators via functional metabotropic receptors in the ventral respiratory group of neonatal mice

GLIA, Issue 8 2009
Kai Härtel
Abstract A controlled, periodic exchange of air between lungs and atmosphere requires a neuronal rhythm generated by a network of neurons in the ventral respiratory group (VRG) of the brainstem. Glial cells, e.g. astrocytes, have been shown to be supportive in stabilizing this neuronal activity in the central nervous system during development. In addition, a variety of neuromodulators including serotonin (5-HT), Substance P (SP), and thyrotropin-releasing hormone (TRH) stimulate respiratory neurons directly. If astrocytes in the VRG, like their neuronal neighbors, are also directly stimulated by neuromodulators, they might indirectly affect the respiratory neurons and consequently the respiratory rhythm. In the present study, we provide support for this concept by demonstrating expression of NK1-R, TRH-R, and 5-HT2 -R in astrocytes of the VRG with immunohistochemistry. Additionally, we showed that the external application of the neuromodulators 5-HT, SP, and TRH activate calcium transients in VRG astrocytes. Consequently, we postulate that in the VRG of the neonatal mouse, neuromodulation by SP, TRH, and serotonin also involves astrocytic calcium signaling. © 2008 Wiley-Liss, Inc. [source]

Location and properties of respiratory neurones with putative intrinsic bursting properties in the rat in situ

THE JOURNAL OF PHYSIOLOGY, Issue 13 2009
Walter M. St.-John
Using the in situ arterially perfused preparations of both neonatal and juvenile rats, we provide the first description of the location, morphology and transmitter content of a population of respiratory neurones that retains a bursting behaviour after ionotropic receptor blockade. All burster neurones exhibited an inspiratory discharge during eupnoeic respiration. These neurones were predominantly glutamatergic, and were located within a region of the ventral respiratory column that encompasses the pre-Bötzinger complex and the more caudally located ventral respiratory group. Bursting behaviour was both voltage and persistent sodium current dependent and could be stimulated by sodium cyanide to activate this persistent sodium current. The population of burster neurones may overlap with that previously described in the neonatal slice in vitro. Based upon the present and previous findings, we hypothesize that this burster discharge may be released when the brain is subject to severe hypoxia or ischaemia, and that this burster discharge could underlie gasping. [source]

Pattern Formation And Rhythm Generation In The Ventral Respiratory Group

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 1-2 2000
Donald R McCrimmon
SUMMARY 1. There is increasing evidence that the kernel of the rhythm-generating circuitry for breathing is located within a discrete subregion of a column of respiratory neurons within the ventrolateral medulla referred to as the ventral respiratory group (VRG). It is less clear how this rhythm is transformed into the precise patterns appearing on the varied motor outflows. 2. Two different approaches were used to test whether subregions of the VRG have distinct roles in rhythm or pattern generation. In one, clusters of VRG neurons were activated or inactivated by pressure injection of small volumes of neuroactive agents to activate or inactivate groups of respiratory neurons and the resulting effects on respiratory rhythm and pattern were determined. The underlying assumption was that if rhythm and pattern are generated by neurons in different VRG subregions, then we should be able to identify regions where activation of neurons predominantly alters rhythm with little effect on pattern and other regions where pattern is altered with little effect on rhythm. 3. Based on the pattern of phrenic nerve responses to injection of an excitatory amino acid (DL -homocysteate), the VRG was divided into four subdivisions arranged along the rostrocaudal axis. Injections into the three rostral regions elicited changes in both respiratory rhythm and pattern. From rostral to caudal the regions included: (i) a rostral bradypnoea region, roughly associated with the Bötzinger complex; (ii) a dysrhythmia/tachypnoea area, roughly associated with the pre-Bötzinger complex (PBC); (iii) a second caudal bradypnoea area; and, most caudally, (iv) a region from which no detectable change in respiratory motor output was elicited. 4. In a second approach, the effect of unilateral lesions of one subregion, the PBC, on the Breuer,Hering reflex changes in rhythm were determined. Activation of this reflex by lung inflation shortens inspiration and lengthens expiration (TE). 5. Unilateral lesions in the PBC attenuated the reflex lengthening of TE, but did not change baseline respiratory rhythm. 6. These findings are consistent with the concept that the VRG is not functionally homogeneous, but consists of rostrocaudally arranged subregions. Neurons within the so-called PBC appear to have a dominant role in rhythm generation. Nevertheless, neurons within other subregions contribute to both rhythm and pattern generation. Thus, at least at an anatomical level resolvable by pressure injection, there appears to be a significant overlap in the circuitry generating respiratory rhythm and pattern. [source]