beta1- and beta2-adrenoceptor induced synaptic facilitation in rat basolateral amygdala

The expression and characteristics of beta-adrenoceptor subtypes (beta1 and beta2) and their agonist actions on synaptic transmission in the basolateral amygdala (BLA) of the rat were examined using in situ hybridization, quantitative real-time PCR, Western blot analysis and field potential recording. In situ hybridization data revealed an intense distribution of beta1-and beta2-adrenoceptor mRNA in the BLA. Real-time PCR analysis of rat amygdala revealed significant transcriptional expression levels of both beta-adrenoceptors, with beta2-adrenoceptors outnumbering beta1-adrenoceptors in a ratio of 2.9 to 1. Bath application of the selective beta1-adrenoceptor agonist xamoterol hemifumarate (10 microM) facilitated the excitatory field synaptic potential evoked in the BLA by stimulation of the external capsule by 186.5+/-10.7% of control amplitude. In the presence of the selective beta1-adrenoceptor antagonist betaxolol hydrochloride (30 microM), the facilitating effects of field excitatory synaptic potential induced by the agonist were reduced to 126.1+/-2.3 % of control amplitude in the BLA. Bath application of the selective beta2-adrenoceptor agonist salmeterol (15 microM) facilitated the excitatory field synaptic potential evoked in the BLA by stimulation of the external capsule by 167.3+/-9.7 % of control amplitude. In the presence of the selective beta2-adrenoceptor antagonist ICI 118,551 HCl (30 microM), the facilitating effects of field excitatory synaptic potential induced by the agonist were reduced to 121.1+/-4.1 % of control amplitude in the BLA. These data suggest that beta-adrenoceptor mediated synaptic facilitation in the amygdala is mediated by both beta1 and beta2-adrenoceptor activation.