Contributions of glucocorticoid receptors in cortical astrocytes to memory recall.

Dysfunctions in memory recall lead to pathological fear; a hallmark of trauma-related disorders, like posttraumatic stress disorder (PTSD). Both, heightened recall of an association between a cue and trauma, as well as impoverished recall that a previously trauma-related cue is no longer a threat, result in a debilitating fear toward the cue. Glucocorticoid-mediated action via the glucocorticoid receptor (GR) influences memory recall. This literature has primarily focused on GRs expressed in neurons or ignored cell-type specific contributions. To ask how GR action in nonneuronal cells influences memory recall, we combined auditory fear conditioning in mice and the knockout of GRs in astrocytes in the prefrontal cortex (PFC), a brain region implicated in memory recall. We found that knocking out GRs in astrocytes of the PFC disrupted memory recall. Specifically, we found that knocking out GRs in astrocytes in the PFC (AstroGRKO) after fear conditioning resulted in higher levels of freezing to the CS+ tone when compared with controls (AstroGRintact). While we did not find any differences in extinction of fear toward the CS+ between these groups, AstroGRKO female but not male mice showed impaired recall of extinction training. These results suggest that GRs in cortical astrocytes contribute to memory recall. These data demonstrate the need to examine GR action in cortical astrocytes to elucidate the basic neurobiology underlying memory recall and potential mechanisms that underlie female-specific biases in the incidence of PTSD.

Different affinities of native alpha1B-adrenoceptors for ketanserin between intact tissue segments and membrane preparations.

The pharmacological profiles of alpha1-adrenoceptors for ketanserin, prazosin, silodosin, and BMY 7378 (8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]decane-7,9-dione dihydrochloride) were examined under different assay conditions. Among the tested antagonists and alpha1-adrenoceptors subtypes, ketanserin showed significantly lower affinity for the alpha1B-adrenoceptor subtype in intact tissue sampled from the rat tail artery, thoracic aorta, and cerebral cortex (functional pKB and binding pKi were approximately 6), than in cerebral cortex membrane preparations or whole cell and membrane preparations of alpha1B-adrenoceptor transfected human embryonic kidney 293T (HEK 293T) cells (pKi was approximately 8). In these tissues and cells, however, ketanserin showed a similar affinity (pKi = approximately 8) for alpha1A- and alpha1D-adrenoceptors even though the assays were conducted under different conditions. In contrast, the affinities of alpha1A-, alpha1B-, and alpha1D-adrenoceptors for prazosin, silodosin, and BMY 7378 did not significantly change under different assay conditions and in different tissues. The present study reveals that the pharmacological profiles of native alpha 1B-adrenoceptors for ketanserin is strongly influenced by the assay conditions and suggest that antagonist affinity is not necessarily constant.

Assessment of muscarinic receptor subtypes in human and rat lower urinary tract by tissue segment binding assay.

Muscarinic receptors in the human and rat lower urinary tract (urinary bladder detrusor muscle and mucosa, and prostate) were identified by intact tissue segment binding assays with two radioligands, and the effects of prolonged receptor activation in vitro on muscarinic receptors were examined. Hydrophilic [(3)H]-NMS and hydrophobic [(3)H]-QNB bound to the detrusor muscle segments with the same density, suggesting that the muscarinic receptors were localized at the plasma membrane. While the density of muscarinic receptor was higher in detrusor muscle than in the bladder mucosa and prostate, there was no species-specific difference either in density or in subtype distribution (M(1), M(2), and M(3) subtypes in detrusor; M(2) and M(3) subtypes in bladder mucosa; and M(1) and M(2) subtypes in prostate). Incubation of detrusor strips with carbachol decreased [(3)H]-NMS binding sites within 20 min, followed by a reduction of [(3)H]-QNB binding sites after a 60-min lag phase. The loss of the binding sites over 3 h after carbachol treatment was the same (approximately 40%) for both radioligands. The present intact tissue segment binding assay reveals tissue-specific and plasma membrane distribution of distinct muscarinic receptor subtypes and their dynamic changes (internalization and down-regulation) in lower urinary tract of humans and rats.