Microinjection of L-glutamate into the nucleus tractus solitarii increases arterial pressure in conscious rats.
Microinjection of L-glutamate into the nucleus tractus solitarii (NTS) of anesthetized rats produces a fall in mean arterial pressure (MAP) similar to that observed during activation of baroreceptor afferents. In the present study we examined the effect of bilateral microinjections of L-glutamate through chronically implanted cannulae in the NTS of conscious freely moving rats. Group I (n = 6) was studied under conscious conditions and 24 h later the rats were anesthetized with urethane and the effects of L-glutamate re-examined. In conscious rats, L-glutamate (30 pmol to 5 nmol/100 nl) produced dose-dependent increases in MAP (+37 +/- 7 mmHg, 5 nmol), whereas under urethane anesthesia falls in MAP were observed (-11 +/- 3 mmHg, 5 nmol). Group II (n = 7) was studied under conscious conditions and 1 h later the rats were anesthetized with chloralose and the effects of L-glutamate re-examined. In this group of conscious rats L-glutamate (300 pmol to 5 nmol/100 nl) also produced dose-dependent increases in MAP (+37 +/- 5 mmHg, 5 nmol), whereas under chloralose anesthesia a dose-dependent depressor response was observed (-33 +/- 6 mmHg, 5 nmol). Saline microinjections into the NTS of conscious and anesthetized rats produced negligible effects. These data demonstrate that microinjection of L-glutamate into the NTS of rats produces a pressor response in conscious animals in contrast to depressor responses in animals anesthetized with chloralose or urethane.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Physiology, School of Medicine of Ribeirão Preto, University of São Paulo, Brazil.
B H
BH
Machado
L G
LG
Bonagamba
D000768:Anesthesia, General; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001933:Brain Stem / Q000033:anatomy & histology / Q000166:cytology; D003243:Consciousness; D004305:Dose-Response Relationship, Drug; D005971:Glutamates / Q000008:administration & dosage / Q000494:pharmacology*; D018698:Glutamic Acid; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000502:physiology*; D008845:Microinjections; D051381:Rats; D011919:Rats, Inbred Strains; D014520:Urethane
D005971:Glutamates; D014520:Urethane; D018698:Glutamic Acid