Kinetic analysis of a transient potassium current in rat cerebellar granule cells in vitro]

Thin slices were prepared from cerebella of 10-24 day old rats and examined with whole-cell patch-clamp methods. Depolarizing steps from holding potentials negative to -60 mV elicited an early transient outward current, identified as IA, and a late outward K+ current. Depolarizations from -50 mV failed to evoke any A current and gave only a slowly rising component similar to the delayed K+ current, which inactivated thereafter with a time constant of 2.5 s at -30 mV. The IA peaked in 1-2 ms, decayed following a double exponential with time constants of 8.1 and 53.2 ms at +20 mV and was half-inactivated at -82.5 mV. 4-AP 4 mM depressed both K+ currents showing little specificity between them, while TEA 20 mM selectively abolished only the delayed K+ current.     

Brain endorphins: possible role in reward and memory formation.

A role for enkephalin in the mediation of behavioral reinforcement is supported by several lines of evidence: i) central injections of enkephalin serve as reinforcement for self-administration behavior, ii) electrical stimulation of many enkephalin-rich regions serves as reinforcement for self-stimulation behavior, which is blocked by moderate doses of naloxone, and iii) long-term retention of a passive avoidance response is facilitated by immediate post-learning injections of methionine-enkephalin and morphine.