Re-evaluation of the effects of norepinephrine on the single-unit activity of paraventricular neurosecretory neurons.
Electrical stimulation of the A1 noradrenergic region elicited predominantly an excitatory orthodromic response from paraventricular neurosecretory neurons recorded in urethane-anesthetized male rats. In a majority of cases, locally applied norepinephrine (NE) as well as A1 region stimulation excited paraventricular neurosecretory neurons. However, in some neurons including a subpopulation of putative vasopressin neurons, iontophoresed NE was inhibitory. Both excitatory and inhibitory effects of NE were selectively blocked by the alpha-antagonist, phentolamine, but not by the beta-antagonist, timolol. In general, the results support the notion that the A1 noradrenergic input to paraventricular neurosecretory neurons is excitatory. Nevertheless, the results do not exclude the possibility that NE exerts a specific, alpha-receptor-mediated, inhibitory effect on a subpopulation of paraventricular neurons.
Kim
Y I
YI
Department of Physiology, University of Texas, Southwestern Medical Center, Dallas 75235.
Dudley
C A
CA
Moss
R L
RL
D000200:Action Potentials / Q000187:drug effects; D000320:Adrenergic Fibers / Q000502:physiology*; D000818:Animals; D004558:Electric Stimulation; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology*; D010121:Oxytocin / Q000378:metabolism; D010286:Paraventricular Hypothalamic Nucleus / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010904:Pituitary Gland, Posterior / Q000502:physiology; D051381:Rats; D011919:Rats, Inbred Strains; D014667:Vasopressins / Q000378:metabolism
D014667:Vasopressins; D010121:Oxytocin; D009638:Norepinephrine; D010646:Phentolamine