Immunocytochemical localisation of neuropeptide Y and 5-hydroxytryptamine in a subpopulation of amine-handling intracardiac neurones that do not contain dopamine β-hydroxylase in tissue culture

Abstract

The colocalisation of neuropeptide Y (NPY)- and 5-hydroxytryptamine (5-HT)-immunoreactivities in intracardiac neurones in dissociated cultures from the atria and interatrial septum of newborn guinea pig heart was demonstrated by the sequential application of specific antisera which were visualised by two different fluorochromes. In this way it was observed that most 5-HT-immunoreactive neurones also contained NPY-immunoreactivity (approximately 40% of identified neurones), some neurones were 5-HT-immunoreactive alone (approximately 10%), while neurones that were NPY-immunoreactive only were rarely seen. No dopamine β-hydroxilase (DBH)-immunoreactive intracardiac neurones were demonstrated in any of the culture preparations studied, although DBH-immunoreactive neurones could be detected in sections of the newborn guinea pig heart containing intracardiac ganglia. The possible implications of the colocalisation of 5-HT, that has been taken up from the culture medium, with NPY in a population of intracardiac neurones are discussed; and reasons for the loss of expression of DBH by these neurones under the conditions of culture are considered.