Peripheral chemoreceptor activation enhances 5-hydroxytryptamine release in the locus coeruleus of conscious rats

Intravenous bolus injection of KCN (40 mu g) elicited brief but pronounced tachypnea, bradycardia and presser response, and led to a 37% increase in 5 -hydroxytryptamine (serotonin) (5-HT) release in the locus coeruleus (LC) o f freely moving rats. Slow infusion of KCN (15 mu g/min) for 10 min induced only a slight presser response, but increased the respiration rate (+39 br eaths/min), as well as 5-HT release in the LC (+60%) throughout the infusio n. In rats with transected chemoreceptor afferents, neither injection or in fusion of KCN changed 5-HT release, suggesting that in intact animals, the effect on extracellular 5-HT was due to activation of peripheral chemorecep tors. In summary, we report that peripheral chemoreceptor activation enhanc es 5-HT release in the LC, indicating that 5-HT might be involved in the mo dulation of LC activity by ascending chemosensory information. (C) 2000 Els evier Science Ireland Ltd. All rights reserved.