Antecedent tone presentation differentially alters the rate of amygdala kindling: continued exposure is not required for this region-specific effect.

Recently we reported that antecedent tone presentation significantly delays the rate of amygdala kindling when it precedes and overlaps with every kindling trial. The goal of the present study was to determine if there is a minimal number of pairings required for the tone to exert its effects or if continued exposure is required. To investigate this, male Long-Evans hooded rats were implanted with a bipolar electrode in the right amygdala and assigned to a Tone, No Tone, or Tone Discontinued group and kindled once daily. The Tone group was exposed to the auditory stimulus on every kindling trial, while the Tone Discontinued group received it for only the first 5 days and subsequently was kindled in the same manner as the No Tone group (i.e., not exposed to the tone while receiving the kindling stimulation). In agreement with our earlier report, antecedent tone presentation significantly delayed seizure progression for subjects kindled in the central nucleus. However, the antecedent tone also significantly accelerated epileptogenesis for rats kindled in the amygdalostriatal transition area and produced no significant difference for those kindled in the basolateral nucleus. Furthermore, presentation of the tone was not required with every kindling trial in order for these effects to be seen, suggesting that a critical period might exist early in the kindling process during which epileptogenesis is acutely vulnerable to intervention. Additional research is necessary to determine the nature of these interventions and what effects they may have on seizure genesis.