Submitted on November 19, 2004
Accepted on December 20, 2004
Postnatal developmental expressions of neurotransmitters and receptors in various brain stem nuclei of rats
Qiuli Liu1 and Margaret T.T. Wong-Riley1*
1 Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
* To whom correspondence should be addressed. E-mail: mwr{at}mcw.edu.
Previously, we reported that the expression of cytochrome oxidase (CO) in a number of brain stem nuclei exhibited a plateau or reduction at postnatal day (P) 3-4 and a dramatic decrease at P12, against a general increase with age. The present study examined the expression of glutamate, N-methyl-D-aspartate receptor subunit 1 (NMDAR1), gamma aminobutyric acid (GABA), GABAB receptors, glycine receptors, and glutamate receptor subunit 2 (GluR2) in the ventrolateral subnucleus of the solitary tract nucleus (NTSVL), nucleus ambiguus (Amb), hypoglossal nucleus (XII), medial accessory olivary nucleus (IOma), dorsal motor nucleus of the vagus (DMNX), and cuneate nucleus (CN), from P2 to P21 in rats. Results showed that: 1) the expression of glutamate increased with age in a majority of the nuclei, whereas that of NMDAR1 showed heterogeneity among the nuclei; 2) GABA and GABAB expressions decreased with age, while that of glycine receptors increased with age; 3) GluR2 showed two peaks: at P3-4 and P12; and 4) glutamate and NMDAR1 showed a significant reduction, while GABA, GABAB receptors, glycine receptors, and GluR2 exhibited a concomitant increase at P12. These features were present but less pronounced in XII and DMNX, and absent in the CN. These data suggest that brain stem nuclei directly or indirectly related to respiratory control share a common developmental trend with the pre-Botzinger complex in having a transient period of imbalance between inhibitory and excitatory drives at P12. During this critical period, the respiratory system may be more vulnerable to excessive exogenous stressors.
