Postnatal expression of neurotransmitters, receptors, and cytochrome oxidase in the rat pre-Bötzinger complex

Abstract

Liu, Qiuli, and Margaret T. T. Wong-Riley. Postnatal expression of neurotransmitters, receptors, and cytochrome oxidase in the rat pre-Bötzinger complex. J Appl Physiol 92: 923-934, 2002; 10.1152/japplphysiol.00977.2001.-The preBötzinger complex (PBC) is postulated as the center of respiratory rhythmogenesis. Previously, we found a reduction or plateau of cytochrome oxidase (CO) activity in the PBC and other respiratory nuclei at postnatal days 3-4, despite a general increase of CO with age, suggesting a period of synaptic readjustment. The present study examined the expression of CO and a number of neurochemicals in the PBC at closer time intervals. At postnatal days 3-4 and, more prominently, at postnatal day 12, expression of CO, glutamate, and N-methyl-D-aspartate receptor subunit 1 was reduced, whereas expression of GABA, GABAB receptor, glycine receptor, and ␣-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor subunit 2 was increased. These findings are consistent with our hypothesis that decreased CO activity is associated with an increase in inhibitory drive (mediated by GABA and glycine, their receptors, and possibly blockage of Ca 2ϩ entry by glutamate receptor subunit 2) and a decrease in excitatory drive (mediated by glutamate and its receptors). Our findings point to two critical periods during postnatal development of the rat when their respiratory system may be more vulnerable to respiratory insults.N-methyl-D-aspartate receptor subunit 1; glutamate receptor subunit 2; GABAB receptor; neurokinin-1 receptor; glutamate THE MECHANISM OF RESPIRATORY rhythmogenesis is not fully understood, but cumulative evidence suggests that the pre-Bötzinger complex (PBC) may be the center or kernel of respiratory rhythm generation (12,37,38,42). The PBC is located at the rostroventrolateral medulla, ventral to the nucleus ambiguus (NA), and can be anatomically defined by the distribution of immunoreactive neurokinin-1 receptors (NK1R) (15). Removal of only the PBC in the brain stem eliminated respiratory rhythm generation in neonatal rats (42). All six basic types of respiratory neurons were identified in the PBC (9, 42), and neurons with voltagedependent pacemaker-like properties were also found there (6,7,17,22,47). It has been implied that the PBC functions as a central hypoxia chemosensor for respiration (44,45). The application of agonists and antagonists of some neurotransmitters and neuromodulators to the PBC can induce apparent changes in respiratory rhythm and pattern (8,21,34,41,43). However, very little is known about postnatal development of neurochemicals in the PBC when the system may be more vulnerable to respiratory distress.Cytochrome oxidase (CO) is the terminal enzyme of the mitochondrial respiratory chain and is considered to be a reliable marker of neurons' metabolic capacity and levels of functional activity (51). Previously, we found that the PBC and other respiratory nuclei in the rat exhibited a general increase in CO activity with postnatal development. However, there was a distin...

Postnatal changes in cytochrome oxidase expressions in brain stem nuclei of rats: implications for sensitive periods

“…We found that, against a general increase in CO with age from postnatal days (P) 0-21, there was a plateau or reduction of CO activity on P3-P4 and a dramatic drop of enzyme levels on P12 (22,24). This was accompanied by a concomitant decrease in excitatory neurotransmitter glutamate and its N-methyl-D-aspartate receptor subunit 1 and an increase in inhibitory neurotransmitters GABA, its receptors (GABA B ), and glycine receptors.…”

“…This was accompanied by a concomitant decrease in excitatory neurotransmitter glutamate and its N-methyl-D-aspartate receptor subunit 1 and an increase in inhibitory neurotransmitters GABA, its receptors (GABA B ), and glycine receptors. The glutamate receptor GluR2, which reduces the permeability of DL-␣-amino-3-hydroxy-5-methylisoxazolepropionic acid receptors to Ca 2ϩ and thereby reduces neuronal excitation, also exhibited an increase during those two periods (22). These findings suggest that, during postnatal development of the rat, there may be two critical periods, P3-P4 and especially P12, when its respiratory system may be under a stronger inhibitory than excitatory drive and may render the animal more vulnerable to respiratory insults.…”

Differential Plasticity of the GABAergic and Glycinergic Synaptic Transmission to Rat Lumbar Motoneurons after Spinal Cord Injury

“…The monoclonal mouse antibody bd-17 (US Biological, bovine, cat # G1016; 1:400) directed against both ␤2 and ␤3 subunits of GABA A Rs, recognize the major GABA A R subtypes in the CNS (McKernan and Whiting, 1996) expressed during postnatal development (Alvarez et al, 1996) and in adult spinal cord motoneurons (Fritschy et al, 1994;Bohlhalter et al, 1996). The mature form of the GlyR, GlyR␣1, was detected with either the monoclonal antibody mAb2b (Connex, mouse, 1:80, catalog # 28 120 501-0 and Synaptic Systems (SySy), mouse 1:250, catalog # 146 111) or the polyclonal antibody pAb2b (Millipore Bioscience Research Reagents, rabbit, 1:100; catalog # AB5052), depending on the other primary antibodies used for double immunofluorescence staining (Pfeiffer et al, 1984;Schröder et al, 1991;Liu and Wong-Riley, 2002;Baer et al, 2003). Both monoclonal or the polyclonal antibodies against GlyR␣1 displayed punctuate fluorescence outlining the cell bodies and dendrites of motoneurons, and a quantitative analysis showed 95% colocalization of the fluorescent clusters when using both antibodies (Lorenzo et al, 2007).…”

Fluorescent Tagging of Rhythmically Active Respiratory Neurons within the Pre-Bötzinger Complex of Rat Medullary Slice Preparations

“…2c,f ), and preBötC (Fig. 2d,g,h) (Horie et al, 2000;Liu and Wong-Riley, 2002;Pagliardini et al, 2003). To further correlate the internalization of TMR-SubP with NK1R expression, treated slices were processed for immunohistochemical detection of NK1R.…”