title: Naloxone prevents the facilitatory effect upon retention induced by adrenaline administration in rats.
abstract: The possible involvement of endogenous opioid peptides in the development of the facilitatory effect of adrenaline on memory has been investigated. For this purpose post-training administration of adrenaline and/or naloxone was carried out in rats tested in an inhibitory avoidance paradigm and subjected or not to pre-training (extensive familiarization with the training situation prior to the acquisition trial). Adrenaline injected subcutaneously in a dose of 500 micrograms/kg facilitated retention performance in rats both subjected or not to pre-training. Naloxone administered SC (400 micrograms/rat) did not influence retention behaviour in rats subjected or not to pre-training, nor did ICV (0.80 ng/rat) administration. Interestingly, the opiate antagonist when injected SC (400 micrograms/rat) prevented the facilitatory effect exerted by adrenaline in pretrained as well as in not pre-trained rats. However, ICV administration of naloxone (0.80 microgram/rat) dit not influence the behavioral effects exerted by the bioamine. These data suggested a role of endogenous opioid peptides on the facilitatory effect of adrenaline on memory, possibly independent of novelty factors and thus of the brain beta-endorphin system. In addition, our results point to the periphery as the most likely site for such interaction.
mesh_terms: D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D004837:Epinephrine / Q000494:pharmacology*; D007276:Injections, Intraventricular; D007279:Injections, Subcutaneous; D007858:Learning / Q000187:drug effects*; D008297:Male; D009270:Naloxone / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D009270:Naloxone; D004837:Epinephrine