ALTERATIONS OF BETA-ENDORPHIN-LIKE IMMUNOREACTIVITY IN CSF FOLLOWING BEHAVIORAL-TRAINING USING A PASSIVE-AVOIDANCE PROCEDURE

The central opioid system may have an important influence on memory pr ocesses. In view of this, the concentration of beta-endorphin-like imm unoreactivity (beta-ELIR) in cerebrospinal fluid (CSF) was measured by a radioimmunoassay in rats trained in a passive avoidance procedure. The beta-ELIR in CSF was examined immediately, 2, 5, 10, and 30 min af ter the learning trial in which rats were exposed to footshock (0, 0.2 5, or 1.0 mA for 3 s). Avoidance latency and beta-ELIR in CSF were exa mined 24 and 120 h after the learning trial. The beta-ELIR in CSF was increased at 5 min after the learning trial in rats exposed to footsho ck of 0.25 mA. The beta-ELIR in CSF was elevated at 5 and 10 min, foll owed by a significant decrease at 30 min after the learning trial in r ats exposed to a footshock of 1.0 mA. Thus, although an increase in be ta-ELIR in CSF was not, the duration of the increase was, related to t he shock intensity. Interestingly, a decrease followed the increase in beta-ELIR in CSF which was significant only in rats exposed to the hi gh shock intensity. Avoidance latencies were enhanced in a shock inten sity-dependent manner at both 24 and 120 h retention tests. No change in beta-ELIR in CSF was found during retention trials. The results sug gest that behavioral manipulations alter beta-ELIR in CSF. An increase in beta-ELIR in CSF may be highly associated with stressful and emoti onal responses during behavioral training. Copyright (C) 1996 Elsevier Science Ltd