title: Excitatory amino acid receptors in the dorsomedial hypothalamus are involved in the cardiovascular and behavioural chemoreflex responses.
abstract: The present study investigated the role of the dorsomedial hypothalamus (DMH) on cardiovascular and behavioural responses of chemoreflex activation in conscious rats. The arterial chemoreflex was activated by potassium cyanide (KCN, 40 μg, i.v.) before and after bilateral microinjection of lidocaine (2%) or kynurenic acid (2.7 nmol) into the DMH. Locomotor activity was measured to assess the chemoreflex behavioural response. Bilateral microinjection of lidocaine into the DMH produced a significant reduction in the pressor response induced by chemoreflex activation (+51 ± 4 versus +34 ± 5 mmHg, n = 5, P < 0.05). A similar reduction in the pressor chemoreflex response was also observed after microinjection of kynurenic acid into the DMH (+50 ± 3 versus +22 ± 5 mmHg, n = 6, P < 0.05). Strikingly, the behaviour/locomotor activity induced by chemoreflex activation was virtually abolished after blockade of excitatory amino acid receptors in the DMH with kynurenic acid (44 ± 6 versus 5 ± 4 cm, n = 6, P < 0.05). There was no correlation between the reduction in pressor and behavioural chemoreflex responses (r = -0.186, P > 0.05). The bradycardic response of the chemoreflex was not altered by lidocaine or kynurenic acid microinjected into the DMH. These results strongly suggest that the excitatory amino acid receptors in the DMH are essential for full expression of the behavioural response of the chemoreflex and participate, at least in part, in the integration of the pressor response of the chemoreflex in conscious rats.
authors.affiliation: Department of Physiology and Biophysics, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
authors.forename: Edson Alexandre
authors.initials: EA
authors.lastname: Queiroz
authors.forename: Marcos Noboru
authors.initials: MN
authors.lastname: Okada
authors.forename: Ubirajara
authors.initials: U
authors.lastname: Fumega
authors.forename: Marco Antônio Peliky
authors.initials: MA
authors.lastname: Fontes
authors.forename: Márcio Flávio Dutra
authors.initials: MF
authors.lastname: Moraes
authors.forename: Andréa Siqueira
authors.initials: AS
authors.lastname: Haibara
mesh_terms: D000818:Animals; D017704:Baroreflex / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology*; D002628:Chemoreceptor Cells / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D017470:Receptors, Glutamate / Q000378:metabolism*
chemical_list: D017470:Receptors, Glutamate