PRIMING OF EXPERIMENTAL ANXIETY BY REPEATED SUBTHRESHOLD GABA BLOCKADE IN THE RAT AMYGDALA

Blockade of GABA(A) receptor function in the area of the anterior baso lateral amygdala of rats elicits physiological (increases in heart rat e and blood pressure) and behavioral changes similar to symptoms of hu man anxiety states. Repeated subthreshold blockade of GABA(A) receptor s in this region appears to result in a long-term 'priming' of these a nxiety-like responses. The present study was conducted to characterize the 'priming' of the heart rate and blood pressure responses and to t est if these 'primed' animals would show increases in anxiety response s. Male Wistar rats with arterial catheters placed for physiological m easurements were implanted with chronic microinjection cannulae in the anterior basolateral amygdaloid nucleus (BLA) under pentobarbital ane sthesia. Repeated daily injections of a subthreshold dose of bicuculli ne methiodide (GABA(A) receptor antagonist; BMI) into the BLA elicited 'priming' of physiological responses after 3-5 injections and this re sponse was maintained for at least 6 weeks. The primed animals also sh owed increased anxiogenic responses to GABA(A) blockade in the BLA. Th e 'priming' of anxiety responses were clearly elicited before kindling of seizures as measured by EEG. These results suggest that this 'prim ing' phenomenon may be similar to kindling and long-term potentiation. This could be one potential mechanism for developing pathological emo tional responses, such as chronic, high levels of anxiety.