Role of periaqueductal gray on the cardiovascular response evoked by disinhibition of the dorsomedial hypothalamus.
Activation of neurons in the region of the dorsomedial hypothalamus (DMH), by microinjection of the GABA(A) receptor antagonist bicuculline methiodide (BMI) results in increases in arterial pressure, heart rate as well as behavioral changes similar to those evoked by acute emotional stress. Previous anatomic studies clearly demonstrated projections from the DMH to the midbrain periaqueductal gray (PAG), a brain region implicated in the organization of behavioral strategies associated with specific cardiovascular responses. In this study, physiological experiments in conscious rats were used to investigate the functional significance of this pathway. Unilateral inhibition of the lateral dorsolateral region of the PAG (l/dlPAG) with the GABA(A) receptor agonist, muscimol (1 nmol/100 nl) largely reduced the tachycardia and the pressor response produced by microinjection of BMI (10 pmol/100 nl) into the ipsilateral DMH. In contrast, inhibition of the ventrolateral PAG (vlPAG) region had no significant effect on the cardiovascular response evoked from disinhibition of the ipsilateral DMH. Our present results indicate that the l/dlPAG region is an important synaptic relay in the descending cardiovascular pathways from the DMH.
da Silva
Luiz Gonzaga
LG
Laboratório de Hipertensão, Departamento de Fisiologia e Biofísica, ICB-UFMG, Universidade Federal de Minas Gerais, , Belo Horizonte, MG 31270 901 Brazil.
de Menezes
Rodrigo Cunha Alvim
RC
dos Santos
Robson Augusto Souza
RA
Campagnole-Santos
Maria Jose
MJ
Fontes
Marco Antonio Peliky
MA
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D002319:Cardiovascular System / Q000187:drug effects; D004302:Dorsomedial Hypothalamic Nucleus / Q000187:drug effects / Q000502:physiology*; D018755:GABA Agonists / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D010487:Periaqueductal Gray / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar
D018755:GABA Agonists