Enhancement of noradrenergic neurotransmission in the nucleus of the solitary tract modulates memory storage processes.
These studies examined whether posttraining activation of alpha1-noradrenergic receptors in the nucleus tractus solitarius (NTS) influences neural processes that are involved in encoding information into memory. Different groups of male Sprague-Dawley rats were trained in two separate learning tasks. In experiment 1, rats were given either a control solution or the alpha1-noradrenergic agonist phenylephrine (0.5, 1.0, 5.0, or 10 microg/0.5 microl) directly into the NTS immediately after they were given a footshock (0.35 mA, 0.5 s) in the dark compartment of an inhibitory apparatus. In a retention test given 48 h later, groups that received either 5.0 or 10.0 microg of phenylephrine avoided the dark compartment for a significantly longer period of time than the PBS control group (P<0.05 and P<0.01, respectively). In experiment 2, identical doses of phenylephrine were infused in the NTS following footshock delivery in one alley of a Y-maze. Animals given either 1.0 or 5.0 microg of phenylephrine performed significantly better than PBS controls on several different measures that served as indices of retention. The results indicate that activation of alpha1-noradrenergic receptors in the NTS plays a critical role in the transmission of signals from the periphery to brain systems that process memory for emotionally significant experiences.
D058646:Adrenergic alpha-1 Receptor Agonists; D000818:Animals; D004305:Dose-Response Relationship, Drug; D008297:Male; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000819:agonists / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D017552:Solitary Nucleus / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*
D058646:Adrenergic alpha-1 Receptor Agonists; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D009638:Norepinephrine