The effects of corticosterone (CS) on single neurones of the brain stem reticular formation (FR), of raphe nuclei (NR) and of locus coeruleus (LC) were studied in rats, anaesthetized in the first case either with urethane or with pentobarbitone sodium, in the other two only with urethane. In the FR. the microelectrophoretic application of CS produced an excitatory effect in 24% of neurones, an inhibition in 23% and no effect in 53% of neurones. The excita- tory effects predominated in the caudal portion of the FR and the inhibitory effects in the rostral FR. No significant differences in the distribution of the effects were observed in relation to the two different anaesthetics. When hydrocortisone (HC) was tested, it behaved similarly to CS. In 27 experiments intravenous injections of CS, which provoked an increase of CS plasma level within the physiological range, were performed, and the effects on the firing rate of a single FR neurone were studied. In all the cases the effects of an intravenous injection of CS on a single FR neurone were similar to those previously obtained on the same neurone by microelectrophoretic application of CS. In the raphe system CS produced an excitatory effect in 61 % and no effect in 39% of neurones. None of the raphe neurones studied was inhibited by CS. In the locus coeruleus CS produced an excitatory effect in 60% of neurones, an inhibition in 4.4% and no effect in 35.6% of neurones. The different effects observed within the brain stem structures studied may be related to their functional differences.
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Con il contributo del Ministero per i Beni e le Attività Culturali