CYCLIC-AMP IN THE RAT CEREBRAL-CORTEX AFTER ACTIVATION OF NORADRENALINE NEURONS OF THE LOCUS COERULEUS

The levels of cyclic AMP in the rat brain were studied in vivo following destruction or stimulation of the noradrenergic pathway originating in the locus coeruleus. After chronic lesion of the locus coeruleus no alterations in cyclic AMP content were found. Electrical stimulation of the locus coeruleus produced an elevation of cyclic AMP in the cerebral cortex of chloral hydrate anaesthetized rats of 30%. Maximal increases were found after 15–60 s stimulation at a frequency of 30–100 Hz. This maximal response was slightly inhibited by phenoxybenzamine, an α‐adrenergic blocking agent, and by the β‐blocker propranolol. When the α and β blockers were administered together a highly significant decrease in cyclic AMP response was observed. Pretreatment of the rats with reserpinc +α methyl‐p‐tyrosine prevented the cyclic AMP response. In addition to the effect in the cerebral cortex, cyclic AMP‐levels were also enhanced in the hippocampus, in the striatum and in the hypothalamus. These results suggest that the locus coeruleus regulates a small fraction of cerebral cyclic AMP levels, by both α‐ and β‐adrenergic receptors. Copyright © 1979, Wiley Blackwell. All rights reserved