Systemic administrations of Naloxone before reward downshift or reward omission

DANERI, M. FLORENCIA; KLIGER, RAFI; PUDDINGTON, MARTIN; MUZIO, RUBEN N.

Cordoba

Congreso; XXXIII Congreso Anual SAN 2018; 2018

Sociedad Argentina de Investigación en Neurociencia

Opioid circuit is part of the mechanisms of physical pain regulation but it could also be implicated in the regulation of psychological pain, the emotional state observed after surprising reward devaluation (successive negative contrast, SNC paradigm) or omission (extinction paradigm). Two experiments are presented using intraperitoneal administration of Naloxone (2mg/kg), an opioid antagonist. In experiment 1, Long Evans rats were trained in an instrumental SNC. Animals received 12 runway preshift sessions reinforced with 32 micropellets, and 10 post shift sessions reinforced with 4 pellets. Their runway performance was compared with animals that always received 4 micropellets. Animals could be assigned to a 32-4 or 4-4 condition and a Saline or Naloxone condition. Injections took place before postshift sessions 1 and 2. Downshifted animals in the saline condition exhibited a runway performance impairment in postshift sessions 5 and 6, and a quick recovery. Animals in the Naloxone condition also exhibited performance impairment but did not showed recovery. In experiment 2, two groups of animals received 12 runway acquisition trials and 10 extinction trials. In extinction trials 1 and 2 a Saline or Naloxone injection was administrated. Both groups differed only in extinction trial 3, where Naloxone group exhibited an increase in runway latency. Both experiments suggest that blocking opioid receptors increases the effect of surprising reward devaluation and omission.