Memory-enhancing effects of post-training dipivefrin and epinephrine: involvement of peripheral and central adrenergic receptors.
These experiments examined the effects, in mice, of post-training i.p. injections of dipivefrin (DPE), a lipophilic prodrug of epinephrine, and epinephrine (EPI) on 48-h retention assessed in inhibitory avoidance and Y-maze discrimination tasks. DPE, in doses of 0.3-10 micrograms/kg significantly facilitated retention: the effects were approximately 10-fold more potent than those of EPI obtained with similar experimental conditions. The alpha-adrenergic antagonists prazosin (alpha 1; 3.0 mg/kg; i.p.), yohimbine (alpha 2; 3.0 mg/kg; i.p.) and phentolamine (alpha 1 and alpha 2; 3.0 mg/kg; i.p.) did not block the enhancement of retention induced by either DPE (10.0 micrograms/kg; i.p.) or EPI (0.1 mg/kg; i.p.). However, the beta-adrenergic antagonist propranolol (2.0 mg/kg; i.p.) attenuated the effects of both DPE and EPI. Sotalol (2.0 mg/kg; i.p.), a peripherally-acting beta-adrenergic antagonist, attenuated the effects of EPI but not those of DPE. These findings suggest the DPE-induced enhancement of memory involves central beta- but not alpha-adrenergic mechanisms while EPI's effects are initiated by activation of peripheral beta-adrenergic systems.
Introini-Collison
I
I
Center for the Neurobiology of Learning and Memory, University of California, Irvine 92717.
Saghafi
D
D
Novack
G D
GD
McGaugh
J L
JL
D018674:Adrenergic Antagonists; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001921:Brain / Q000187:drug effects*; D004193:Discrimination Learning / Q000187:drug effects; D004347:Drug Interactions; D004837:Epinephrine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D010525:Peripheral Nerves / Q000187:drug effects*; D011941:Receptors, Adrenergic / Q000187:drug effects*; D012153:Retention, Psychology / Q000187:drug effects*; D013997:Time Factors
D018674:Adrenergic Antagonists; D011941:Receptors, Adrenergic; C015173:dipivefrin; D004837:Epinephrine