Gzα deficient mice: enzyme levels in the autonomic nervous system, neuronal survival and effect of genetic background

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Abstract
Our laboratory has generated a genetically mutant mouse in which the alpha subunit of the heterotrimeric GTP binding protein, G z has been made dysfunctional by homologous recombination to determine its in vivo function. These animals show a characteristic failure to thrive phenotype. G zα is expressed in a variety of nervous system tissues as well as in the adrenal medulla. We therefore examined the autonomic nervous system of the G zα deficient mouse by measuring the activity of tyrosine hydroxylase and choline acetyltransferase in the superior cervical ganglia, submaxillary gland and the adrenal medulla. Preliminary results using animals of mixed BALB/c and C57BL/6 strains gave inconsistent results. Further experiments demonstrated differences in the activity of tyrosine hydroxylase and choline acetyltransferase between BALB/c and C57BL/6 mouse strains. The analysis of the pure strains showed a reduction in the size and enzyme levels of the adrenal gland and submaxillary glands of the G zα deficient mouse suggesting a role for adrenal insufficiency and/or nutritional disorders for the failure to thrive phenotype. The survival of sympathetic and sensory neurons was also examined in the G zα deficient mouse and in the presence of pertussis toxin, sympathetic but not sensory neuronal survival in G zα deficient mice was significantly attenuated. This suggests that in vivo other pertussis toxin sensitive G proteins may be recruited to compensate for the loss of G zα .