The endogenous opioid peptides, met- or leu-enkephalin, and corticotropin-releasing factor (CRF) regulate noradrenergic neurons in the locus coeruleus (LC) in a convergent manner via projections from distinct brain areas. In contrast, the opioid peptide dynorphin (DYN) has been shown to serve as a co-transmitter with CRF in afferents to the LC. To further define anatomical substrates targeting noradrenergic neurons by DYN afferents originating from limbic sources, anterograde tract-tracing of biotinylated dextran amine (BDA) from the central amygdaloid complex was combined with immunocytochemical detection of DYN and tyrosine hydroxylase (TH) in the same section of tissue. Triple labeling immunocytochemistry was combined with electron microscopy in the LC where BDA was identified using an immunoperoxidase marker, and DYN and TH were distinguished by the use of sequential immunogold labeling and silver enhancement to produce different sized gold particles. Results show direct evidence of a monosynaptic pathway linking amygdalar DYN afferents with LC neurons. To determine whether DYN-containing amygdalar LC projecting neurons colocalize CRF, retrograde tract-tracing using fluorescent latex microspheres injected into the LC was combined with immunocytochemical detection of DYN and CRF in single sections in the central amygdala. Retrogradely labeled neurons from the LC were distributed throughout the rostro-caudal extent of the central nucleus of the amygdala (CeA) as previously described. Cell counts showed that approximately 42% of LC-projecting neurons in the CeA contained both DYN and CRF. Taken with our previous studies showing monosynaptic projections from amygdalar CRF neurons to noradrenergic LC cells, the present study extends this by showing that DYN and CRF are co-transmitters in monosynaptic projections to the LC and are poised to coordinately impact LC neuronal activity.

Activation of the hypothalamo-pituitary-adrenal axis by bacterial lipopolysaccharide (LPS; endotoxin) is well documented, although there has been uncertainty about whether LPS exerts a direct effect at the level of the adrenal. The present study found that LPS caused a dose-dependent stimulation of basal cortisol secretion by the human adrenocortical cell line, NCI-H295R, without affecting aldosterone. The expression of both Toll-like receptor 2 (TLR2) and TLR4 was demonstrated in these cells, and the specific ligands for TLR4 (purified LPS and lipid A) and TLR2 (Pam3Cys) were found to stimulate cortisol release, suggesting that these receptors may mediate the effects of LPS in adrenal cells, as has been shown in other cell types. LPS was also found to stimulate prostaglandin E2 release by these cells. The effects of LPS on cortisol were attenuated in the presence of both indomethacin and a specific COX-2 inhibitor, but not a COX-1 inhibitor, suggesting an obligatory role for COX-2 activation and prostaglandin synthesis in the adrenal response to LPS.

The recently reported superiority of mechanical thrombectomy to intravenous thrombolytics has jettisoned endovascular intervention into the forefront of acute ischemic stroke (AIS) management. These successes have allowed a chance for recanalization for patients not meeting the strict eligibility criteria for intravenous thrombolytics. Stent retrieval and aspiration have emerged as two of the most popular and effective approaches for AIS thrombectomy. Since the beginning of mechanical thrombectomy with the Merci device (Stryker) and first-generation Penumbra aspiration system (Penumbra Inc), contemporary techniques have demonstrated reliable recanalization and improved clinical outcomes. Here, we review the use of stent retrieval and aspiration, as well as their synergy, in the management of AIS.