Estimating the synaptic concentration of norepinephrine in dentate gyrus which produces beta-receptor mediated long-lasting potentiation in vivo using microdialysis and intracerebroventricular norepinephrine.
Norepinephrine in the hippocampus of urethane anesthetized rats was monitored by microdialysis prior to, and following, an intracerebroventricular injection of 5 micrograms [-]NE in 2 microliters of ACSF. The perforant path evoked potential in dentate gyrus was concurrently monitored by a microelectrode adjacent to the dialysis probe. NE levels 30 x basal values or greater at the recording site were related to long-lasting potentiation of the perforant path-evoked population spike. Increases of 3 x to 6 x basal NE values were not accompanied by any potentiation. NE in the midline ventricles alone did not produce potentiation. These results suggest effective NE concentrations for beta-receptor activation of long-term potentiation would only occur near the NE release site.
Harley
C W
CW
Psychology Department, Memorial University of Newfoundland, St. John's Canada. charley@kean.ucs.mun.ca
Lalies
M D
MD
Nutt
D J
DJ
D000200:Action Potentials; D000818:Animals; D005071:Evoked Potentials; D006624:Hippocampus / Q000502:physiology*; D007276:Injections, Intraventricular; D017774:Long-Term Potentiation / Q000502:physiology*; D008297:Male; D017551:Microdialysis; D009638:Norepinephrine / Q000378:metabolism*; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013569:Synapses / Q000378:metabolism*
D011943:Receptors, Adrenergic, beta; D009638:Norepinephrine