Glutamatergic receptors of the rostral ventrolateral medulla are involved in the ventilatory response to hypoxia.
Rostral ventrolateral medulla (RVLM) is a region in the brainstem that is involved in the physiologic responses to hypoxia (i.e. hyperventilation and regulated hypothermia) and contains l-glutamate receptors. Therefore, we examined the effects of blocked of glutamatergic receptors in the RVLM on hypoxic hyperventilation and regulated hypothermia. Ventilation (V(E)) and body temperature (T(b)) were measured before and after bilaterally microinjection of kynurenic acid (KYN, 5 nmol/100 nl, an ionotropic glutamatergic receptors antagonist) and alpha-methyl-4-carboxyphenylglycine (MCPG, 10 nmol/100 nl, a metabotropic glutamatergic receptors antagonist) into the RVLM, followed by a 60-min period of hypoxia exposure. Control rats received microinjection of saline (vehicle). KYN or MCPG into the RVLM did not change V(E) and T(b) under normoxia, but reduced the hypoxic hyperventilation due to a lower tidal volume, although regulated hypothermia persisted. These data suggest that glutamatergic receptors in the RVLM are involved in the ventilatory response to hypoxia, exercising an excitatory modulation of the RVLM neurons, but play no role in hypoxia-induced hypothermia.
de Paula
Patricia M
PM
Departamento de Ciencias Biologicas, Faculdade de Medicina do Triangulo Mineiro, Uberaba, MG, Brazil. depaula@uthscsa.edu
Branco
Luiz G S
LG
D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D001831:Body Temperature / Q000502:physiology; D001833:Body Temperature Regulation / Q000187:drug effects; D004347:Drug Interactions; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006985:Hyperventilation / Q000503:physiopathology; D007035:Hypothermia / Q000139:chemically induced / Q000503:physiopathology; D000860:Hypoxia / Q000503:physiopathology*; D007736:Kynurenic Acid / Q000494:pharmacology; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000503:physiopathology*; D008845:Microinjections / Q000379:methods; D012123:Pulmonary Ventilation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000502:physiology*; D013990:Tidal Volume / Q000187:drug effects; D013997:Time Factors; D012122:Ventilators, Mechanical
D001565:Benzoates; D018691:Excitatory Amino Acid Antagonists; D017470:Receptors, Glutamate; C079694:alpha-methyl-4-carboxyphenylglycine; D007736:Kynurenic Acid; D005998:Glycine