Whole-cell patch clamp recordings were made in a pontine slice preparation of the rat brain containing the nucleus locus coeruleus (LC). In a first series of experiments, it was demonstrated that tyrosine hydroxylase-positive LC neurons of young (10-14 days of age) rats are multipolar with numerous dendrites. When pipettes filled with the marker molecule biocytin were used for recording, all cells exhibiting outward current responses to noradrenaline (100 μM) showed the morphology typical for LC neurons. At a holding potential of -80 mV, noradrenaline (100 μM) produced a comparably small outward current both in LC neurons of young (8-14 days) and older (18-23 days) rats. In contrast, 2-methylthio ATP (2-MeSATP; 100 μM) caused a relatively small inward current in the young animals, while inward current responses were much larger in most older animals (8 out of a total of 11). It is suggested that after birth there are probably no functional P2 purinoceptors present at LC neurons. Thereafter, P2 purinoceptor-function increases with age, reaching maturity only in animals older than 18 days.
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