Sodium lactate elicits anxiety in rats after repeated GABA receptor blockade in the basolateral amygdala

Repeated administration of the GABA(A) receptor antagonist bicuculline meth iodide into the basolateral nucleus of the amygdala at doses subthreshold t o eliciting a full response will eventually produce long-term 'priming', su ch that heart rate, blood pressure as well as anxiety are increased at the lower doses. The present study was conducted in order to determine if the l ong-term priming of anxiety within the basolateral nucleus is producing a c ondition similar to that seen in human panic disorder by testing the respon se elicited by i.v, lactate infusions, since lactate infusions induce a pan ic attack in patients with panic disorder. Male Wistar rats were fitted wit h femoral arterial and venous catheters and chronic microinjection cannulae into the basolateral nucleus. Repeated daily injections of a subthreshold dose of bicuculline methiodide into the basolateral nucleus for 4-5 days el icited a primed response, while the same procedure with artificial cerebros pinal fluid vehicle (a-CSF; sham-primed) had no effect. Following priming, rats received both sodium lactate infusions (0.5 N, 10 ml/kg) or 0.9% salin e in a random order separated by 48 h. Heart rate and blood pressure were m onitored throughout the infusion and the animals were immediately placed in the social interaction test to assess their anxiety response. Only primed and not sham-primed rats responded to a lactate infusion with significant i ncreases in heart rate, blood pressure and experimental anxiety. Thus, rats which are primed with chronic subthreshold GABA receptor blockade in the b asolateral nucleus develop a sensitivity to sodium lactate, similar to huma n panic disorder patients. (C) 2000 Elsevier Science B.V. All rights reserv ed.