“…For systemic administration and in vitro experiments, the chosen single doses of the antagonists were similar to the ones used by previous authors (Morgan and Teyler, 1999;Borroni et al, 2000;Freir and Herron, 2003;Niikura et al, 2004;Woodside et al, 2004), which correspond to dose levels at which the actions of the drugs are likely to be mainly on L-type VDCCs; at higher concentrations, actions have been reported on potassium channels and nicotinic receptors (Hume, 1985;Zhang et al, 1999;Houlihan et al, 2000;Madeja et al, 2000). That the same pattern of memory impairment was seen with exemplars of all three groups of antagonists, which bind to different regions of the channel (Striessnig et al, 1990Nakayama et al, 1991;Nakayama and Kuniyasu, 1996;Hockerman et al, 2000), adds weight to the conclusion that the effects of the drugs are attributable to antagonism of L-type VDCCs. The parallel results produced by the localized infusion of verapamil establish that an action within the PRH region is sufficient to produce memory impairment.…”