Changes in the expression of alpha(2)-adrenergic receptor subtypes during maturation of neuronal cells from fetal pig superior cervical ganglia

The expression of presynaptic alpha(2)-adrenereic receptor (alpha(2)-AR) su btypes was investigated in cultured neurons from fetal pig superior cervica l ganglion (SCG). Cells were incubated with chicken antibodies against alph a(2)A-, alpha(2)B- or alpha(2)C-AR subtypes either alone or together with a ntibodies against dopamine-beta-hydroxylase (D beta H, a marker for adrener gic neurons) or against choline acetyl transferase (ChAT, a marker for chol inergic neurons). We found immunoreactivity for ail three alpha(2)-AR subty pes in SCG-cells when cultured for 8-11 days. The relative expression of th e alpha(2)A-subtype was approximately 1/3 of that of alpha(2)B- and alpha(2 )C-AR. Co-localisation of all three alpha(2)-AR subtypes was observed in ce lls expressing DPH or ChAT. Increasing the potassium concentration in the c ulture medium increased the expression of DPH and decreased the expression of the alpha(2)A- and alpha(2)C-subtype without altering the expression of the alpha(2)B-subtype. Co-culture of neurons with pig splenocytes enhanced the expression of ChAT and decreased the expression of the alpha(2)B-subtyp e without altering the expression of alpha(2)A- and alpha(2)C-subtypes. Our results indicate that the three alpha(2)-receptor subtypes are expressed o n both noradrenergic and cholinergic nerves. Induction of the noradrenergic phenotype favours the expression of the alpha(2)B-subtype over that of the alpha(2)A- and alpha(2)C-subtype. Conversely, enhancement of the cholinerg ic phenotype favours the expression of the alpha(2)A- and alpha(2)C-subtype s over that of the alpha(2)B-subtype. Our results suggest that the alpha(2) B-receptor is preferentially associated with noradrenergic nerve endings. ( C) 1999 Elsevier Science B.V. All rights reserved.