Pharmaco-behavioural evidence indicating a complex role for ryanodine receptor calcium release channels in memory processing for a passive avoidance task

Calcium signalling is an important process underlying neuronal function and consequently behaviour. The release of calcium from intracellular stores via the ryanodine receptor calcium release (RyR) channel has been implicated in both synaptic plasticity and to a limited extent in memory processing. While past investigations have suggested a role for RyR channels in long-term memory, the present study suggests their action is more complex. Using a single trial passive avoidance task developed for the day-old chick, it is proposed that RyR channels are necessary both prior to the expression of long-term memory and also in retrieval processes. Specifically, 5 mM dantrolene (a specific RyR channel blocker) resulted in a persistent retention loss from 40 min post-training while 10 nM dantrolene produced a transient retention loss centred at 40 min post-training. We speculate that in the context of memory formation, RyR channels may be activated by nitric oxide and in the context of memory retrieval may lead to the activation of large conductance calcium-activated potassium BK(Ca) channels which, when blocked by 50 nM iberiotoxin, also demonstrated a transient retention loss centred at 40 min post-training.