DIFFERENTIAL AGE-DEPENDENT EXPRESSION OF ALPHA(2) ADRENOCEPTOR-FUNCTION AND P2 PURINOCEPTOR-FUNCTION IN RAT LOCUS-COERULEUS NEURONS

Whole-cell patch clamp recordings were made in a pontine slice prepara tion of the rat brain containing the nucleus locus coeruleus (LC). In a first series of experiments, it was demonstrated that tyrosine hydro xylase-positive LC neurons of young (10-14 days of age) rats are multi polar with numerous dendrites. When pipettes filled with the marker mo lecule biocytin were used for recording, all cells exhibiting outward current responses to noradrenaline (100 mu M) showed the morphology ty pical for LC neurons. At a holding potential of -80 mV, noradrenaline (100 mu M) produced a comparably small outward current both in LC neur ons of young (8-14 days) and older (18-23 days) rats. In contrast, 2-m ethylthio ATP (2-MeSATP; 100 mu M) caused a relatively small inward cu rrent in the young animals, while inward current responses were much l arger in most older animals (8 out of a total of 11). It is suggested that after birth there are probably no functional P2 purinoceptors pre sent at LC neurons. Thereafter, P2 purinoceptor-function increases wit h age, reaching maturity only in animals older than 18 days.