title: Pressor and tachycardic responses evoked by microinjections of L-glutamate into the medial prefrontal cortex of unanaesthetized rats.
abstract: The ventral medial prefrontal cortex (vMPFC) is involved in central cardiovascular control. In the present study, we studied the cardiovascular effects of injections of L-glutamate into the vMPFC of unanaesthetized rats and the mechanisms of these effects. Male Wistar rats were used and L-glutamate was microinjected in the vMPFC in a final volume of 200 nL. Microinjections of L-glutamate (9, 27, 81, 150 or 300 nmol) caused long-lasting, dose-related pressor and tachycardic responses in unanaesthetized rats. No differences were observed among cardiovascular responses when L-glutamate was injected into the three sub-areas that comprise the vMPFC, namely the prelimbic, the infralimbic and the dorsal peduncular cortices. No responses were observed when the dose of 81 nmol of L-glutamate was microinjected into surrounding structures such as the cingulate cortex area 1, the corpus callosum and the tenia tecta, indicating a predominant action on the vMPFC. The cardiovascular response to L-glutamate into the vMPFC was blocked by intravenous pretreatment with the ganglion blocker pentolinium (10 mg/kg, i.v.) or the beta1-adrenoceptor antagonist atenolol (1.5 mg/kg, i.v.), supporting the involvement of the cardiac sympathetic nervous system in the response to L-glutamate. Pretreatment with the muscarinic antagonist homatropine methyl bromide (1 mg/kg, i.v.) reduced the latency to the onset of the pressor and tachycardic responses to L-glutamate injected into the vMPFC without significant effects on response duration or maximum effect. We conclude that stimulation of the vMPFC with L-glutamate caused pressor and tachycardic responses in unanaesthetized rats, responses which were dependent on cardiac sympathetic nerve activation and were potentiated by blockade of peripheral muscarinic receptors.
authors.affiliation: Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Ribeirão Preto, SP, 14049-900, Brazil.
authors.forename: L B M
authors.initials: LB
authors.lastname: Resstel
authors.forename: F M A
authors.initials: FM
authors.lastname: Corrêa
mesh_terms: D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001262:Atenolol / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D003337:Corpus Callosum / Q000187:drug effects / Q000502:physiology; D018698:Glutamic Acid / Q000494:pharmacology*; D006179:Gyrus Cinguli / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008845:Microinjections; D010425:Pentolinium Tartrate / Q000494:pharmacology; D017397:Prefrontal Cortex / Q000187:drug effects* / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012965:Sodium Chloride / Q000494:pharmacology; D013268:Stimulation, Chemical; D013610:Tachycardia / Q000139:chemically induced / Q000503:physiopathology*; D014326:Tropanes / Q000494:pharmacology; D014851:Wakefulness
chemical_list: D000959:Antihypertensive Agents; D014326:Tropanes; D018698:Glutamic Acid; D012965:Sodium Chloride; D001262:Atenolol; C056244:homatropine methylbromide; D010425:Pentolinium Tartrate