Microdialysis in the posterior hypothalamus: sodium chloride affects norepinephrine release, mean arterial pressure, heart rate and behavior in awake rats.
A microdialysis probe, implanted in the posterior hypothalamus (PH) was used to examine changes of extracellular norepinephrine (NE) in freely moving rats from which mean arterial pressure (mAP) and heart rate (HR) were continuously monitored. Artificial cerebrospinal fluid (aCSF) was pumped through the probe and 10-microliters dialysate samples were collected at 5-minute intervals and analyzed for NE by radioenzymatic assay. High sodium chloride (NaCl)-aCSF solution elicited pressor and tachycardiac responses and locomotor activity coupled with significant increases in levels of dialysate NE. The latter and the associated cardiovascular effects were significantly attenuated by perfusate lidocaine (0.5%). When alpha-adrenergic receptors in PH were blocked by phenoxybenzamine (0.165 M), high NaCl-aCSF released NE but the associated cardiovascular effects were attenuated. In addition, intravenous ganglionic blockade with hexamethonium (25 mg/kg) also attenuated cardiovascular responses during the high NaCl-aCSF perfusion of PH. These results indicate that PH is one of the important areas for central actions of NaCl and that the cardiovascular and locomotor responses produced by central NaCl, in part, depend on neuroadrenergic activity in PH.
Nakata
T
T
University of Southern California School of Medicine, Department of Medicine, Los Angeles 90033.
Berard
W
W
Kogosov
E
E
Alexander
N
N
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002555:Cerebrospinal Fluid / Q000502:physiology; D003956:Dialysis / Q000379:methods*; D004058:Diffusion; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D018738:Hexamethonium; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007034:Hypothalamus, Posterior / Q000187:drug effects* / Q000378:metabolism; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D009043:Motor Activity / Q000187:drug effects*; D009638:Norepinephrine / Q000378:metabolism*; D010643:Phenoxybenzamine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000008:administration & dosage / Q000494:pharmacology*
D000959:Antihypertensive Agents; D006584:Hexamethonium Compounds; D010643:Phenoxybenzamine; D010656:Phenylephrine; D018738:Hexamethonium; D012965:Sodium Chloride; D008012:Lidocaine; D009638:Norepinephrine