Effects of pituitary adenylate cyclase polypeptide (PACAP) on extinction of active avoidance learning in rats: Involvement of neurotransmitters

Agnes Adamik, Gyula Telegdy

Research output: Contribution to journalArticle

12 Citations (Scopus)


The effects of PACAP-38 on the extinction of active avoidance learning were studied in rats. The action of transmitter mediation was followed by pretreating the animals with appropriate receptor antagonists. PACAP-38 administered into the lateral brain ventricle caused a transitory facilitation of the extinction of a learned active avoidance response at 3 and 6 h following extinction, which had returned to or even above the control level at the 24-h testing. PACAP 6-38, which is an antagonist of PACAP-38, and an antibody against PACAP-38, prevented this action. When the animals were retested during a further 10 days, the control animals demonstrated response extinction on day 7, while the PACAP-38-treated animals still showed a high proportion (70%) of positive responses. The following receptor blockers diminished the action of PACAP-38 on the facilitation of extinction: propranolol, haloperidol, naloxone, bicuculline and nitro-l-arginine, the latter by blocking nitric oxide formation. Phenoxybenzamine and atropine were ineffective. The data reveal that the transitory action of PACAP-38 within 24 h on the facilitation of extinction is mediated by beta-adrenergic, dopaminergic, GABA-ergic and opiate receptors and nitric oxide. This transitory facilitated extinction is caused partly by depressed locomotion and presumably also an increased body temperature. Following a transitory facilitation of extinction from 24 h on, PACAP-38 demonstrated a greatly delayed extinction, which lasted for more than 7 days, while the control animals displayed complete extinction. The data suggest that PACAP-38 facilitates memory retrieval processes in the extinction of the active avoidance reflex.

Original languageEnglish
Pages (from-to)55-62
Number of pages8
JournalRegulatory Peptides
Issue number1-3
Publication statusPublished - Apr 15 2005


  • Behavior
  • Neuropeptides
  • Receptors
  • Transmitters

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Endocrinology
  • Clinical Biochemistry
  • Cellular and Molecular Neuroscience

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