The diagonal band of Broca is involved in the pressor pathway activated by noradrenaline microinjected into the periaqueductal gray area of rats.
OBJECTIVE
The dorsal periaqueductal gray area (dPAG) is involved in cardiovascular modulation. Previously, we reported that noradrenaline (NA) microinjection into the dPAG caused a pressor response that was mediated by vasopressin release into the circulation. However, the neuronal pathway that mediates this response is as yet unknown. There is evidence that chemical stimulation of the diagonal band of Broca (dbB) also causes a pressor response mediated by systemic vasopressin release. In the present study, we evaluated the participation of the dbB in the pressor response caused by NA microinjection into the dPAG as well as the existence of neural connections between these areas.


METHODS
With the above goal, we verified the effect of the pharmacological ablation of the dbB on the cardiovascular response to NA microinjection into the dPAG of unanesthetized rats. In addition, we microinjected the neuronal tracer biotinylated-dextran-amine (BDA) into the dPAG and looked for efferent projections from the dPAG to the dbB.


RESULTS
The pharmacologically reversible ablation of the dbB with local microinjection of CoCl(2) significantly reduced the pressor response caused by NA microinjection (15 nmol/50 nL) into the dPAG. In addition, BDA microinjection into the dPAG labeled axons in the dbB, pointing to the existence of direct connections between these areas.


CONCLUSIONS
The present results indicate that synapses within the dbB are involved in the pressor pathway activated by NA microinjection into the dPAG and direct neural projection from the dPAG to the dbB may constitute the neuroanatomic substrate for this pressor pathway.
Pelosi
Gislaine Garcia
GG
Department of Pharmacology, School of Medicine of Ribeirão Preto, University of São Paulo, Av. Bandeirantes 3900, 14040-900, Ribeirão Preto, São Paulo, Brazil. pelosigg@yahoo.com.br
Tavares
Rodrigo Fiacadori
RF
Corrêa
Fernando Morgan Aguiar
FM
D000818:Animals; D001710:Biotin / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001931:Brain Mapping; D003035:Cobalt / Q000494:pharmacology; D003911:Dextrans / Q000494:pharmacology; D020667:Diagonal Band of Broca / Q000187:drug effects* / Q000502:physiology; D004525:Efferent Pathways / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D008297:Male; D008845:Microinjections; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D010487:Periaqueductal Gray / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013569:Synapses / Q000187:drug effects / Q000502:physiology
D003911:Dextrans; C076397:biotinylated dextran amine; D003035:Cobalt; D001710:Biotin; C018021:cobaltous chloride; D009638:Norepinephrine