Actions of norepinephrine in the rat hippocampus.
Acting at postsynaptic alpha 1- and beta 1-receptors, norepinephrine (NE) exerts a complex action in rat hippocampus. It is currently believed that beta 1-receptor activation enhances excitability of recorded neurons, whereas alpha 1 activation suppresses reactivity to afferent stimulation. These reported effects of alpha-agonists are not consistent with alpha 1 effects found elsewhere in the brain. We have conducted experiments in the anesthetized rat and found that an amphetamine-induced increase in the dentate gyrus population spike can be blocked by a beta-antagonist but also by an alpha 1-antagonist. We have conducted experiments in the brain slide preparation and found that an alpha-agonist, phenylephrine (PHE), selectively enhances responses to N-methyl-D-aspartate (NMDA) but not to quisqualate. We propose that the product of activation of both alpha- and beta-receptor types will enhance reactivity of hippocampal cells to afferent stimulation.
Segal
M
M
Center for Neurosciences, Weizmann Institute, Rehovot, Israel.
Markram
H
H
Richter-Levin
G
G
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D004357:Drug Synergism; D006624:Hippocampus / Q000187:drug effects / Q000502:physiology*; D008125:Locus Coeruleus / Q000502:physiology*; D016202:N-Methylaspartate / Q000494:pharmacology; D009638:Norepinephrine / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D016318:Quisqualic Acid / Q000494:pharmacology; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000502:physiology
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D016202:N-Methylaspartate; D016318:Quisqualic Acid; D009638:Norepinephrine