Histamine Is A Possible New Neurotransmitter In The Cardiac Sympathetic Nerve

The histaminergic nerves exit in the hypothamus mainly and the histaminergic nervous system was found hi the brain, but there was little study on the presence of histamine in peripheral nerve system. The histidine decarboxylase is the only enzyme that catalyzes histidine into histamine, so it is regarded as the marker of the histaminergic cell. Accordingly, using in situ hybridization histochemistry technology with specific oligonucleotide probe and immunohistochemistry technology with anti-histamine antibody, the histidine decarboxylase rnRNA hybridization signal and histamine positive signal were detected in the superior cervical ganglia. The releasing of histamine was also detected in the isolated atrium of guinea pig, but it reduced greatly in the isolated atrium of resipined guinea pig. Therefore, histamine may be synthesized in the sympathetic nerve and modulates important neurotransmission such as NE in the heart, participates the normal physiology processes.1 The expression of histidine decarboxylase (HDC) in the superior cervical ganglion of guinea pigUsing in situ hybridization histochemistry technology with specificoligonucleotide probe, the postival signal was detected in the suprior cervical ganglion (SCO) of guinea pig. There were lots of cells containing the HDC, and the postival signal was detected in both of large and small cells. Because the HDC is the only enzyme which catalyzes histidine into histamine, it seems that the histamine can been synthesed in the SCO.2 The coexistance of histamine and tyrosine hydroxylase(TH) in the superior cervical ganglion of guinea pigUsing immunohistochemistry technology with anti-histamine antibody and anti-TH antibody^ the fluorescent antibody: fluorescein isothiocyanate and tetramethylrhodamine isothiocyanat, both immunoreactive materials were detected in the same cells of guinea pig superior cervical ganglion. The TH immunoreactive substance distributed in cytoplasm steadly with negative nuclei, while the histamine immunoreactive substance distributed in cytoplasm nearby the plasmalemma. After chemical destroy of the guinea pig SCO's sympathetic neuron with 6-(OH)-DA, the immunoreactive materials were hardly detected, it indicated that histamine exists in the sympathetic neuron.3 The releasing of histamine in the sympathetic nerve of guinea pig isolated atriumIt has been reported that histamine had been present in guinea pig hearts, in order to study whether histamine exists in the sympathetic nerve of guinea pig heart, we used spectrofluorometer to detect the releasing of histamine from isolated guinea pig atria stimulated by field electronic stimulator(109.67 ?8.88 ng/ml, n=8). Compound 48/80(100 ng/ml) was added 2-3 times to the isolated guinea pig atria to degrenuate histamine from mast cell(297.50?88.68 ng/ml , n=8) totally, then histamine was still detected using spectrofluorometer, and the releasing of histamine was reduced in the respined isolated guinea pig atria(29.17?1.29 ng/ml. n=8) comparing with the normal group. So it can be concluded that histamine presents in the sympathetic nerve of guinea pig atrium.