Search

The bed nucleus of the stria terminalis (BNST) plays a critical role in regulating the behavioral response to stress. Stressors that activate the BNST also activate serotonergic (5-HT) systems. Hence, maladaptive changes of 5-HT receptor expression may contribute to stress-induced anxiety disorders. The BNST contains three neuronal types, Type I-III neurons. However, little is known about 5-HT receptor subtypes mRNA expression in these neurons, or whether it can be modulated by stress. Whole-cell patch clamp recording from Type I-III neurons was used in conjunction with single cell reverse transcriptase polymerase chain reaction (RT-PCR) to characterize 5-HT receptor mRNA expression, and examine the effects of stress on this expression. We report that Type I neurons expressed mRNA transcripts predominantly for 5-HT(1A) and 5-HT(7) receptors. Type II neurons expressed transcripts for every 5-HT receptor except the 5-HT(2C) receptor. Type II neurons were divided into three sub-populations: Type IIA in which transcripts for 5-HT(3) and 5-HT(7) receptors predominate, Type IIB that mainly express 5-HT(1B) and 5-HT(4) receptor transcripts, and Type IIC in which transcripts for 5-HT(1A) and 5-HT(2A) receptors predominate. Type III neurons were also subdivided into two sub-populations; one that predominantly expressed transcripts for 5-HT(1A), 5-HT(1B) and 5-HT(2A) receptors, and another that mainly expressed transcripts for 5-HT(2C) receptor. Unpredictable shock stress (USS) caused a long-lasting increase in anxiety-like behavior, and a concomitant decrease in 5-HT(1A) transcript expression in Type I-III neurons, as well as an up-regulation of a transcriptional repressor of 5-HT(1A) gene expression, deformed epidermal autoregulatory factor 1 (Deaf-1). Significantly USS decreased 5-HT(1A) protein level, and increased the level of Deaf-1. USS also increased 5-HT(1B) transcript expression in Type III neurons, as well as 5-HT(7) expression in Type I and II neurons. These data suggest that cell type-specific disruption of 5-HT receptor expression in BNST(ALG) neurons may contribute to stress-induced anxiety disorders.

The Kv4 potassium channel α subunits, Kv4.1, Kv4.2, and Kv4.3, determine some of the fundamental physiological properties of neurons in the CNS. Kv4 subunits are associated with auxiliary β-subunits, such as the potassium channel interacting proteins (KChIP1 - 4), which are thought to regulate the trafficking and gating of native Kv4 potassium channels. Intriguingly, KChIP1 is thought to show cell type-selective expression in GABA-ergic inhibitory interneurons, while other β-subunits (KChIP2-4) are associated with principal glutamatergic neurons. However, nothing is known about the expression of Kv4 family α- and β-subunits in specific interneurons populations in the BLA. Here, we have used immunofluorescence, co-immunoprecipitation, and Western Blotting to determine the relative expression of KChIP1 in the different interneuron subtypes within the BLA, and its co-localization with one or more of the Kv4 α subunits. We show that all three α-subunits of Kv4 potassium channel are found in rat BLA neurons, and that the immunoreactivity of KChIP1 closely resembles that of Kv4.3. Indeed, Kv4.3 showed almost complete co-localization with KChIP1 in the soma and dendrites of a distinct subpopulation of BLA neurons. Dual-immunofluorescence studies revealed this to be in BLA interneurons immunoreactive for parvalbumin, cholecystokin-8, and somatostatin. Finally, co-immunoprecipitation studies showed that KChIP1 was associated with all three Kv4 α subunits. Together our results suggest that KChIP1 is selectively expressed in BLA interneurons where it may function to regulate the activity of A-type potassium channels. Hence, KChIP1 might be considered as a cell type-specific regulator of GABAergic inhibitory circuits in the BLA.