Involvement of the periaqueductal gray in the hypotensive response evoked by L-glutamate microinjection in the lateral hypothalamus of unanesthetized rats.
The lateral hypothalamus (LH) is involved in cardiovascular control. L-glutamate (L-glu) stimulation of the LH of unanesthetized rats evoked hypotensive responses without significant heart rate changes. The neuronal pathway that mediates this response is unknown. There is evidence that the periaqueductal gray (PAG) is involved in the mediation of hypotensive responses evoked by electrical stimulation of the LH. In the present study, we attempted to verify the effect of an acute and reversible pharmacological ablation of the PAG with lidocaine or CoCl(2) on the hypotensive response caused by L-glu injection in the LH of unanesthetized rats. Microinjection of the local anesthetic lidocaine or the unspecific synaptic blocker CoCl(2) in the PAG significantly attenuated the hypotensive effects of L-glu stimulation of the LH, indicating the involvement of local synapses within the PAG in the hypotensive pathway activated by LH glutamatergic receptors. Microinjection of the neuronal tracer biotinylated dextran amine (BDA) in the PAG labeled neuronal cell bodies in the LH, indicating the existence of direct connections between these areas. In conclusion, the present results indicate that the hypotensive response evoked by L-glu stimulation of LH may involve a synaptic relay in the dorsal PAG.
Pajolla
Gisela Pugliesi
GP
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
Tavares
Rodrigo Fiacadori
RF
Pelosi
Gislaine Garcia
GG
Corrêa
Fernando Morgan Aguiar
FM
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D018698:Glutamic Acid / Q000008:administration & dosage*; D007022:Hypotension / Q000139:chemically induced / Q000503:physiopathology; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007276:Injections, Intraventricular; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008845:Microinjections; D009434:Neural Pathways / Q000166:cytology*; D009474:Neurons / Q000166:cytology; D010487:Periaqueductal Gray / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D000889:Anti-Arrhythmia Agents; D003035:Cobalt; D018698:Glutamic Acid; D008012:Lidocaine; C018021:cobaltous chloride