Behavioral activation by enkephalins in mice

Intraventricular injection of long lasting enkephalin analogues (D-Ala2 Leu and Met enkephalin-amides) produced a sustained elevation of psychomotor activity in mice. The motor syndromes were characterized by continual stereotyped activity and were reversed by naloxone pretreatment. Naloxone administered to a separate group of mide reduced the initial activation seen after exposure to a novel environment. The present findings suggest one or more endogenous opiates normally facilitates behavioral excitation in mice.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22626/1/0000176.pd