Neurotransmitters in central respiratory control

A diverse group of processes are involved in central control of ventilation . Both fast acting neurotransmitters and slower acting neuromodulators are involved in the central respiratory drive. This review deals with fast acti ng neurotransmitters that are essential centrally in the ventilatory respon se to H+/CO2, and to acute hypoxia. Data are reviewed to show that the cent ral response to H+/CO2 is primarily at sites in the medulla, the most promi nent being the ventral medullary surface (VMS), and that acetylcholine is t he key neurotransmitter in this process. Genetic abnormalities in the choli nergic system lead to states of hypoventilation in man and that knock out m ice for genes responsible for neural cost development have none or diminish ed CO2 ventilatory response. In the acute ventilatory response to hypoxia t he afferent impulses from the carotid body reach the nucleus tractus solita rius (NTS) releasing glutamate which stimulates ventilation. Glutamate rele ase also occurs in the VMS, Hypoxia is also associated with release of GABA in the mid-brain and a biphasic change in concentration of another inhibit ory amino acid, taurine. Collectively changes in these amino acids can acco unt for the ventilatory output in response to acute hypoxia. Future studies should provide more data on molecular and genetic basis of central respira tory drive and the role of neurotransmitter in this essential function. (C) 2000 Elsevier Science B.V. All rights reserved.