Cardiovascular responses to microinjection of l-glutamate into the NTS in AV3V-lesioned rats

• Published in: Brain research Vol. 1025; no. 1; pp. 106 - 112
• Main Authors: Vieira, Alexandre Antonio, Colombari, Eduardo, De Luca, Laurival A., de Almeida Colombari, Débora Simões, Menani, José V.
• Format: Journal Article
• Language: English
• Published: London Elsevier B.V 29.10.2004; Amsterdam Elsevier; New York, NY
• Subjects: Animals; Baroreceptor; Biological and medical sciences; Blood Pressure - drug effects; Blood Pressure - physiology; Cardiovascular System - drug effects; Chemoreceptor; Fundamental and applied biological sciences. Psychology; Glutamic Acid - administration & dosage; Heart Rate - drug effects; Heart Rate - physiology; Hypertension; Hypothalamus; Male; Microinjections - methods; Motor control and motor pathways. Reflexes. Control centers of vegetative functions. Vestibular system and equilibration; Rats; Rats, Sprague-Dawley; Solitary Nucleus - drug effects; Solitary Nucleus - physiology; Solitary tract; Third Ventricle - drug effects; Third Ventricle - physiology; Vertebrates: nervous system and sense organs; Hypertension; Endocrine and autonomic regulation; Baroreceptor; Hypothalamus; Solitary tract; Chemoreceptor; Cardiovascular control; Rat; Rodentia; Central nervous system; Glutamate; Encephalon; Solitary nucleus; Vertebrata; Mammalia; Excitatory aminoacid; Neurotransmitter; Lesion
• ISSN: 0006-8993; 1872-6240
• DOI: 10.1016/j.brainres.2004.08.006

The excitatory amino acid l-glutamate injected into the nucleus of the solitary tract (NTS) in unanesthetized rats similar to peripheral chemoreceptor activation increases mean arterial pressure (MAP) and reduces heart rate. In this study, we investigated the effects of acute (1 day) and chronic (15 days) electrolytic lesions of the preoptic-periventricular tissue surrounding the anteroventral third ventricle (AV3V region) on the pressor and bradycardic responses induced by injections of l-glutamate into the NTS or peripheral chemoreceptor activation in unanesthetized rats. Male Holtzman rats with sham or electrolytic AV3V lesions and a stainless steel cannula implanted into the NTS were used. Differently from the pressor responses (28±3 mm Hg) produced by injections into the NTS of sham-lesioned rats, l-glutamate (5 nmol/100 nl) injected into the NTS reduced MAP (−26±8 mm Hg) or produced no effect (2±7 mm Hg) in acute and chronic AV3V-lesioned rats, respectively. The bradycardia to l-glutamate into the NTS and the cardiovascular responses to chemoreflex activation with intravenous potassium cyanide or to baroreflex activation with intravenous phenylephrine or sodium nitroprusside were not modified by AV3V lesions. The results show that the integrity of the AV3V region is essential for the pressor responses to l-glutamate into the NTS but not for the pressor responses to chemoreflex activation, suggesting dissociation between the central mechanisms involved in these responses.