The Basolateral Amygdala Sends a Mixed (GABAergic and Glutamatergic) Projection to the Mediodorsal Thalamic Nucleus

The medial prefrontal cortex receives converging inputs from the mediodorsal thalamic nucleus (MD) and basolateral amygdala (BLA). Although many studies reported that the BLA also projects to MD, there is conflicting evidence regarding this projection, with some data suggesting that it originates from GABAergic or glutamatergic neurons. Therefore, the present study aimed to determine the neurotransmitter used by MD-projecting BLA cells in male and female rats. We first examined whether BLA cells retrogradely labeled by Fast Blue infusions in MD are immunopositive for multiple established markers of BLA interneurons. A minority of MD-projecting BLA cells expressed somatostatin (∼22%) or calretinin (∼11%) but not other interneuronal markers, suggesting that BLA neurons projecting to MD not only include glutamatergic cells, but also long-range GABAergic neurons. Second, we examined the responses of MD cells to optogenetic activation of BLA axons using whole-cell recordings in vitro Consistent with our immunohistochemical findings, among responsive MD cells, light stimuli typically elicited isolated EPSPs (73%) or IPSPs (27%) as well as coincident EPSPs and IPSPs (11%). Indicating that these IPSPs were monosynaptic, light-evoked EPSPs and IPSPs had the same latency and the IPSPs persisted in the presence of ionotropic glutamate receptor antagonists. Overall, our results indicate that the BLA sends a mixed, glutamatergic-GABAergic projection to MD, which likely influences coordination of activity between BLA, MD, and medial prefrontal cortex. An important challenge for future studies will be to examine the connections formed by MD-projecting glutamatergic and GABAergic BLA cells with each other and other populations of BLA cells.SIGNIFICANCE STATEMENT The mediodorsal thalamic nucleus (MD) and basolateral amygdala (BLA) send convergent projections to the medial prefrontal cortex. Although many studies reported that the BLA also projects to MD, there is conflicting evidence as to whether this projection is glutamatergic or GABAergic. By combining tract tracing, immunohistochemistry, optogenetics, and patch clamp recordings in vitro, we found that BLA neurons projecting to MD not only include glutamatergic cells, but also long-range GABAergic neurons. Differential recruitment of these two contingents of cells likely influences coordination of activity between the BLA, MD, and medial prefrontal cortex.

Associations between anxiety, centromedial amygdala volume, and complex verbal fluency in middle-aged to older adults

Symptoms of anxiety are related to decreases in cognitive performance in middle-aged to older adults (i.e., ages 50 and older; MOA). Verbal fluency (VF), assessed with the Delis-Kaplan Executive Function System (D-KEFS) Category Switching (VF-CS) task, captures elements of executive function such as semantic memory, response initiation and inhibition, and cognitive flexibility. The present study examined the link between anxiety symptoms and VF-CS to better understand how this association affects such executive functions in MOA. We hypothesized that higher subclinical Beck Anxiety Inventory (BAI) scores would be associated with lower VF-CS. To further investigate the underlying neurobiological basis of an expected inverse relationship, total amygdala volume, centromedial amygdala (CMA) volume, and basolateral amygdala (BLA) volume were examined as they related to VF-CS scores on the D-KEFS. Based on extant research on connectivity and functioning between the CMA and BLA, we hypothesized that larger BLA volumes would be associated with lower anxiety scores and exhibit positive relationships with VF-CS. A sample of 63 MOA were recruited from the Providence, Rhode Island area as a part of a parent study on cardiovascular diseases. Participants completed self-report measures about physical and emotional health, a neuropsychological assessment, and a magnetic resonance imaging scan (MRI). Multiple hierarchical regressions were performed to examine relationships between variables of interest. Contrary to hypotheses, no significant relationship emerged between VF-CS and BAI scores, and BLA volume was not associated with either BAI scores or VF-CS. However, a significant positive relationship was observed between CMA volume and VF-CS. The significant relationship found between CMA and VF-CS may reflect the upward slope of the quadratic relationship between arousal and cognitive performance on the Yerkes-Dodson curve. These findings newly implicate CMA volume specifically as a possible neuromarker linking emotional arousal and cognitive performance in MOA.

An Updated Perspective on the Dual-Track Model of Enterocyte Fat Metabolism

The small intestinal epithelium has classically been envisioned as a conduit for nutrient absorption, but appreciation is growing for a larger and more dynamic role for enterocytes in lipid metabolism. Considerable gaps remain in our knowledge of this physiology, but it appears that the enterocyte's structural polarization dictates its behavior in fat partitioning, treating fat differently based on its absorption across the apical versus the basolateral membrane. In this review, we synthesize existing data and thought on this dual-track model of enterocyte fat metabolism through the lens of human integrative physiology. The apical track includes the canonical pathway of dietary lipid absorption across the apical brush-border membrane, leading to packaging and secretion of those lipids as chylomicrons. However, this track also reserves a portion of dietary lipid within cytoplasmic lipid droplets for later uses, including the "second-meal effect," which remains poorly understood. At the same time, the enterocyte takes up circulating fats across the basolateral membrane by mechanisms that may include receptor-mediated import of triglyceride-rich lipoproteins or their remnants, local hydrolysis and internalization of free fatty acids, or enterocyte de novo lipogenesis using basolaterally absorbed substrates. The ultimate destinations of basolateral-track fat may include fatty acid oxidation, structural lipid synthesis, storage in cytoplasmic lipid droplets, or ultimate resecretion, although the regulation and purposes of this basolateral track remain mysterious. We propose that the enterocyte integrates lipid flux along both of these tracks in order to calibrate its overall program of lipid metabolism.

Powassan Viruses Spread Cell to Cell during Direct Isolation from Ixodes Ticks and Persistently Infect Human Brain Endothelial Cells and Pericytes

Powassan viruses (POWVs) are neurovirulent tick-borne flaviviruses emerging in the northeastern United States, with a 2% prevalence in Long Island (LI) deer ticks (Ixodes scapularis). POWVs are transmitted within as little as 15 min of a tick bite and enter the central nervous system (CNS) to cause encephalitis (10% of cases are fatal) and long-term neuronal damage. POWV-LI9 and POWV-LI41 present in LI Ixodes ticks were isolated by directly inoculating VeroE6 cells with tick homogenates and detecting POWV-infected cells by immunoperoxidase staining. Inoculated POWV-LI9 and LI41 were exclusively present in infected cell foci, indicative of cell to cell spread, despite growth in liquid culture without an overlay. Cloning and sequencing establish POWV-LI9 as a phylogenetically distinct lineage II POWV strain circulating in LI deer ticks. Primary human brain microvascular endothelial cells (hBMECs) and pericytes form a neurovascular complex that restricts entry into the CNS. We found that POWV-LI9 and -LI41 and lineage I POWV-LB productively infect hBMECs and pericytes and that POWVs were basolaterally transmitted from hBMECs to lower-chamber pericytes without permeabilizing polarized hBMECs. Synchronous POWV-LI9 infection of hBMECs and pericytes induced proinflammatory chemokines, interferon-β (IFN-β) and proteins of the IFN-stimulated gene family (ISGs), with delayed IFN-β secretion by infected pericytes. IFN inhibited POWV infection, but despite IFN secretion, a subset of POWV-infected hBMECs and pericytes remained persistently infected. These findings suggest a potential mechanism for POWVs (LI9/LI41 and LB) to infect hBMECs, spread basolaterally to pericytes, and enter the CNS. hBMEC and pericyte responses to POWV infection suggest a role for immunopathology in POWV neurovirulence and potential therapeutic targets for preventing POWV spread to neuronal compartments. IMPORTANCE We isolated POWVs from LI deer ticks (I. scapularis) directly in VeroE6 cells, and sequencing revealed POWV-LI9 as a distinct lineage II POWV strain. Remarkably, inoculation of VeroE6 cells with POWV-containing tick homogenates resulted in infected cell foci in liquid culture, consistent with cell-to-cell spread. POWV-LI9 and -LI41 and lineage I POWV-LB strains infected hBMECs and pericytes that comprise neurovascular complexes. POWVs were nonlytically transmitted basolaterally from infected hBMECs to lower-chamber pericytes, suggesting a mechanism for POWV transmission across the blood-brain barrier (BBB). POWV-LI9 elicited inflammatory responses from infected hBMEC and pericytes that may contribute to immune cell recruitment and neuropathogenesis. This study reveals a potential mechanism for POWVs to enter the CNS by infecting hBMECs and spreading basolaterally to abluminal pericytes. Our findings reveal that POWV-LI9 persists in cells that form a neurovascular complex spanning the BBB and suggest potential therapeutic targets for preventing POWV spread to neuronal compartments.

Inhibitory effect of tumor necrosis factor-α on the basolateral Kir4.1/Kir5.1 channels in the thick ascending limb during diabetes

Diabetic nephropathy is a major contributor to the morbidity and mortality of patients with diabetes. TNF-α expression is elevated during diabetes and is implicated in the pathogenesis of diabetic nephropathy; however, its underlying molecular mechanisms remain unclear. The present study aimed to investigate the effect and molecular mechanism of TNF-α on the basolateral inwardly rectifying potassium (Kir)4.1/Kir5.1 channels in the thick ascending limb (TAL) of rat kidneys using western blotting and the patch clamp technique to provide a theoretical basis for the cause of the decrease in kidney concentrating capacity during diabetes. The results demonstrated that urinary TNF-α excretion and protein TNF-α expression in the TAL increased and basolateral Kir4.1/Kir5.1 channel activity decreased during diabetes; however, diabetic rats exhibited amelioration of Kir4.1/Kir5.1 activity with a soluble TNF-α antagonist, TNF receptor fusion protein (TNFR:Fc). These results suggested that TNF-α inhibited the activity of the basolateral Kir4.1/Kir5.1 channel in the TAL of rat kidneys during diabetes. In addition, the protein expression levels of phospholipase A₂ (PLA₂) and cyclooxygenase-₂ (COX₂) increased in diabetic rats, the effects of which deceased following treatment with TNFR:Fc compared with the diabetic group. Furthermore, an agonist of PLA₂ (melittin) and COX₂ production [prostaglandin E₂ (PGE₂)] inhibited the basolateral Kir4.1/Kir5.1 channels. Taken together, the results of the present study suggested that the inhibitory effect of TNF-α on the basolateral Kir4.1/Kir5.1 channels in the TAL during diabetes is mediated by the PLA₂/COX₂/PGE₂ signaling pathway.

Molecular and functional profiling of apical versus basolateral small extracellular vesicles derived from primary human proximal tubular epithelial cells under inflammatory conditions

Proximal tubular epithelial cells (PTEC) are central players in inflammatory kidney diseases. However, the complex signalling mechanism/s via which polarized PTEC mediate disease progression are poorly understood. Small extracellular vesicles (sEV), including exosomes, are recognized as fundamental components of cellular communication and signalling courtesy of their molecular cargo (lipids, microRNA, proteins). In this study, we examined the molecular content and function of sEV secreted from the apical versus basolateral surfaces of polarized human primary PTEC under inflammatory diseased conditions. PTEC were cultured under normal and inflammatory conditions on Transwell inserts to enable separate collection and isolation of apical/basolateral sEV. Significantly increased numbers of apical and basolateral sEV were secreted under inflammatory conditions compared with equivalent normal conditions. Multi‐omics analysis revealed distinct molecular profiles (lipids, microRNA, proteins) between inflammatory and normal conditions for both apical and basolateral sEV. Biological pathway analyses of significantly differentially expressed molecules associated apical inflammatory sEV with processes of cell survival and immunological disease, while basolateral inflammatory sEV were linked to pathways of immune cell trafficking and cell‐to‐cell signalling. In line with this mechanistic concept, functional assays demonstrated significantly increased production of chemokines (monocyte chemoattractant protein‐1, interleukin‐8) and immuno‐regulatory cytokine interleukin‐10 by peripheral blood mononuclear cells activated with basolateral sEV derived from inflammatory PTEC. We propose that the distinct molecular composition of sEV released from the apical versus basolateral membranes of human inflammatory PTEC may reflect specialized functional roles, with basolateral‐derived sEV pivotal in modulating tubulointerstitial inflammatory responses observed in many immune‐mediated kidney diseases. These findings provide a rationale to further evaluate these sEV‐mediated inflammatory pathways as targets for biomarker and therapeutic development.

Differential Recruitment of Competing Valence-Related Amygdala Networks during Anxiety

The basolateral amygdala (BL) is involved in fear and anxiety, but it is currently unclear how the same network supports these two states. To address this question, we trained rats on appetitive and aversive conditioning in different contexts. Distinct groups of BL neurons displayed increased activity during appetitive (CS-R) versus aversive (CS-S) conditioned stimuli (R cells and S cells, respectively), and they were typically inhibited by the other CS. When the CS-S was presented in the safe context, rats entered a long-lasting, anxiety-like state characterized by increased inter-CS freezing and impaired reward seeking. During this state, a subset of BL cells ("state cells") showed sustained shifts in baseline activity whose time course matched that of the behavioral changes. Many state cells with increased firing rates were S cells, whereas R cells only included state cells with reduced firing rates. Thus, anxiety involves persistent activity changes that are differentially expressed by subsets of valence-specific BL neurons.

Spatiotemporal phosphoregulation of Lgl: Finding meaning in multiple on/off buttons

Intracellular asymmetries, often termed cell polarity, determine how cells organize and divide to ultimately control cell fate and shape animal tissues. The tumor suppressor Lethal giant larvae (Lgl) functions at the core of the evolutionarily conserved cell polarity machinery that controls apico-basal polarization. This function relies on its restricted basolateral localization via phosphorylation by aPKC. Here, we summarize the spatial and temporal control of Lgl during the cell cycle, highlighting two ideas that emerged from our recent findings: 1) Aurora A directly phosphorylates Lgl during symmetric division to couple reorganization of epithelial polarity with the cell cycle; 2) Phosphorylation of Lgl within three conserved serines controls its localization and function in a site-specific manner. Considering the importance of phosphorylation to regulate the concentration of Lgl at the plasma membrane, we will further discuss how it may work as an on-off switch for the interaction with cortical binding partners, with implications on epithelial polarization and spindle orientation.

Transcytosis of IL-11 and Apical Redirection of gp130 Is Mediated by IL-11α Receptor

Interleukin (IL)-11 signaling is involved in various processes, including epithelial intestinal cell regeneration and embryo implantation. IL-11 signaling is initiated upon binding of IL-11 to IL-11R1 or IL-11R2, two IL-11α-receptor splice variants, and gp130. Here, we show that IL-11 signaling via IL-11R1/2:gp130 complexes occurs on both the apical and basolateral sides of polarized cells, whereas IL-6 signaling via IL-6R:gp130 complexes is restricted to the basolateral side. We show that basolaterally supplied IL-11 is transported and released to the apical extracellular space via transcytosis in an IL-11R1-dependent manner. By contrast, IL-6R and IL-11R2 do not promote transcytosis. In addition, we show that transcytosis of IL-11 is dependent on the intracellular domain of IL-11R1 and that synthetic transfer of the intracellular domain of IL-11R1 to IL-6R promotes transcytosis of IL-6. Our data define IL-11R as a cytokine receptor with transcytotic activity by which IL-11 and IL-6:soluble IL-6R complexes are transported across cellular barriers.

Impaired acquisition of classically conditioned fear-potentiated startle reflexes in humans with focal bilateral basolateral amygdala damage

Based on studies in rodents, the basolateral amygdala (BLA) is considered a key site for experience-dependent neural plasticity underlying the acquisition of conditioned fear responses. In humans, very few studies exist of subjects with selective amygdala lesions and those studies have only implicated the amygdala more broadly leaving the role of amygdala sub-regions underexplored. We tested a rare sample of subjects (N = 4) with unprecedented focal bilateral BLA lesions due to a genetic condition called Urbach-Wiethe disease. In a classical delay fear conditioning experiment, these subjects showed impaired acquisition of conditioned fear relative to a group of matched control subjects (N = 10) as measured by fear-potentiation of the defensive eye-blink startle reflex. After the experiment, the BLA-damaged cases showed normal declarative memory of the conditioned association. Our findings provide new evidence that the human BLA is essential to drive fast classically conditioned defensive reflexes.

Neonatal olfactory bulbectomy enhances locomotor activity, exploratory behavior and binding of NMDA receptors in pre-pubertal rats

In this study, we investigated the effect of neonatal olfactory bulbectomy (nOBX) on behavioral paradigms related to olfaction such as exploratory behavior, locomotor activity in a novel environment and social interaction. We also studied the effect of nOBX on the activity of the N-methyl-d-aspartate (NMDA) subtype of glutamate receptors during development. The behavioral effects of nOBX (postnatal day 7, PD7) were investigated in pre- (PD30) and post-pubertal (PD60) Wistar rats. NMDA receptor activity was measured with [(125)I]MK-801 in the brain regions associated with the olfactory circuitry. A significant increase in the novelty-induced locomotion was seen in the pre-pubertal nOBX rats. Although the locomotor effect was less marked than in pre-pubertal rats, the nOBX rats tested post-pubertally failed to habituate to the novel situation as quickly as the sham- and normal- controls. Pre-pubertally, the head-dipping behavior was enhanced in nOBX rats compared with sham-operated and normal controls, while normal exploratory behavior was observed between groups in adulthood. In contrast, social interaction was increased in post-pubertal animals that underwent nOBX. Both pre- and post-pubertal nOBX rats recovered olfaction. Interestingly, pre-pubertal rats showed a significant increase in the [(125)I]MK-801 binding in the piriform cortex, dorsal hippocampus, inner and outer layers of the frontal cortex and outer layer of the cingulate cortex. At post-pubertal age, no significant differences in [(125)I]MK-801 binding were observed between groups at any of the brain regions analyzed. These results suggest that nOBX produces pre-pubertal behavioral disturbances and NMDA receptor changes that are transitory with recovery of olfaction early in adulthood.

In vitro to in vivo evidence of the inhibitor characteristics of Schisandra lignans toward P-glycoprotein

Concomitant administration of herbal medicines with drugs that are P-glycoprotein (P-gp) substrates may produce significant herb-drug interactions. The purpose of this study was to evaluate the effects of Schisandra lignans extract (SLE) on P-gp thoroughly in vitro and in vivo, and to investigate the possible P-gp-based herb-drug interactions. In the in vitro experiments, the effect of SLE on the uptake and transport for P-gp substrates in Caco-2, LLC-PK1 and L-MDR1 cells were carefully investigated. Verapamil, a known P-gp inhibitor, was used as a positive control drug. Results shown that, 10 μM verapamil and SLE (0.5, 2.0, and 10.0 μg/ml) were observed to significantly enhance the uptake and inhibit the efflux ratio of P-gp substrates in Caco-2 and L-MDR1 cells. In vivo experiments showed that single-dose SLE at 500 mg/kg could increase the area under the plasma concentration time curve of digoxin and vincrisine significantly without affecting terminal elimination half-time. Long-term treatment with SLE for continuous 10 days could also increase the absorption of P-gp substrates with greatly down regulation of P-gp expression in rat intestinal and brain tissues. In conclusion, SLE was a strong P-gp inhibitor, which indicated a potential herb-drug interaction when SLE was co-administered with P-gp substrate drugs.

Analysis of polarized membrane traffic in hepatocytes and hepatic cell lines

The protocols described in this unit were developed to monitor membrane traffic in cultured cell monolayers that display hepatic polarity. In general, the assays are designed to visualize and/or quantitate membrane trafficking by monitoring the fates of antibodies bound to specific membrane proteins. We first describe how to infect cells with recombinant adenovirus, the preferred method for introducing exogenous genes into hepatic cells. We next provide a morphological assay to monitor basolateral to apical transcytosis. In a supporting protocol, we describe how to visualize apical recycling and/or retention. In an additional supporting protocol, we provide a semi-quantitative method to measure the relative extents of apical delivery. Finally, we describe quantitative assays to measure basolateral internalization and recycling. The methods presented in this unit provide a relatively simple, yet powerful approach to examining hepatic membrane traffic.

The dual-gate lumen model of renal monoamine transport

The three-phase response of urinary serotonin and dopamine in subjects simultaneously taking amino acid precursors of serotonin and dopamine has been defined.1,2 No model exists regarding the renal etiology of the three-phase response. This writing outlines a model explaining the origin of the three-phase response of urinary serotonin and dopamine. A "dual-gate lumen transporter model" for the basolateral monoamine transporters of the kidneys is proposed as being the etiology of the three-phase urinary serotonin and dopamine responses.

PURPOSE

The purpose of this writing is to document the internal renal function model that has evolved in research during large-scale assay with phase interpretation of urinary serotonin and dopamine.

PATIENTS AND METHODS

In excess of 75,000 urinary monoamine assays from more than 7,500 patients were analyzed. The serotonin and the dopamine phase were determined for specimens submitted in the competitive inhibition state. The phase determination findings were then correlated with peer-reviewed literature.

RESULTS

The correlation between the three-phase response of urinary serotonin and dopamine with internal renal processes of the bilateral monoamine transporter and the apical monoamine transporter of the proximal convoluted renal tubule cells is defined.

CONCLUSION

The phase of urinary serotonin and dopamine is dependent on the status of the serotonin gate, dopamine gate, and lumen of the basolateral monoamine transporter while in the competitive inhibition state.

Drosophila Varicose, a member of a new subgroup of basolateral MAGUKs, is required for septate junctions and tracheal morphogenesis

Epithelial tubes are the functional units of many organs, but little is known about how tube sizes are established. Using the Drosophila tracheal system as a model, we previously showed that mutations in varicose (vari) cause tubes to become elongated without increasing cell number. Here we show vari is required for accumulation of the tracheal size-control proteins Vermiform and Serpentine in the tracheal lumen. We also show that vari is an essential septate junction (SJ) gene encoding a membrane associated guanylate kinase (MAGUK). In vivo analyses of domains important for MAGUK scaffolding functions demonstrate that while the Vari HOOK domain is essential, the L27 domain is dispensable. Phylogenetic analyses reveal that Vari helps define a new MAGUK subgroup that includes mammalian PALS2. Importantly, both Vari and PALS2 are basolateral, and the interaction of Vari with the cell-adhesion protein Neurexin IV parallels the interaction of PALS2 and another cell-adhesion protein, Necl-2. Vari therefore bolsters the similarity between Drosophila and vertebrate epithelial basolateral regions, which had previously been limited to the common basolateral localization of Scrib, Dlg and Lgl, proteins required for epithelial polarization at the beginning of embryogenesis. However, by contrast to Scrib, Dlg and Lgl, Vari is not required for cell polarity but rather is part of a cell-adhesion complex. Thus, Vari fundamentally extends the similarity of Drosophila and vertebrate basolateral regions from sharing only polarity complexes to sharing both polarity and cell-adhesion complexes.

Compromised cytoarchitecture and polarized trafficking in autosomal dominant polycystic kidney disease cells

Cystogenesis associated with autosomal dominant polycystic kidney disease (ADPKD) is characterized by perturbations in the polarized phenotype and function of cyst-lining epithelial cells. The polycystins, the protein products of the genes mutated in the majority of ADPKD cases, have been described recently, but the pathological mechanism by which causal mutations result in the mislocalization of cell membrane proteins has remained unclear. This report documents the dissociation from the ADPKD cell basolateral membrane of three molecules essential for spatial organization and exocytosis. The adherens junction protein E-cadherin, the subcellular disposition of which governs intercellular and intracellular architecture, was discovered sequestered in an internal ADPKD cell compartment. At the same time, sec6 and sec8, components of a complex critical for basolateral cargo delivery normally arrayed at the apico-lateral apex, were depleted from the ADPKD cell plasma membrane. An analysis of membrane transport revealed that basolateral trafficking of proteins and lipids was impaired as a result of delayed cargo exit from the ADPKD cell Golgi apparatus. Apical transport proceeded normally. Taken together with recent documentation of an association between polycystin-1 and E-cadherin (Huan and van Adelsberg 1999), the data suggest that causal mutations disrupt E-cadherin-dependent cytoarchitecture, adversely affecting protein assemblies crucial for basolateral trafficking.

Basolateral amygdala is involved in modulating consolidation of memory for classical fear conditioning

Previous findings indicate that the basolateral amygdala complex of nuclei (BLC) is involved in modulating (i.e., enhancing or impairing) memory consolidation for aversive training such as inhibitory avoidance. The present study examined whether the BLC also modulates the consolidation of memory for classical fear conditioning in which a specific context is paired with footshock. Adult male rats with bilateral cannulae targeting the BLC were allowed, first, to habituate in a Y maze that had differently shaped and textured arms. On the next day the rats were placed in one maze arm (shock arm), and they received four unsignaled footshocks. In Experiment 1, immediately after the training some rats received BLC inactivation with lidocaine (10 microgram/0.2 microliter per side), and control rats received buffered saline. In Experiment 2, rats received immediate post-training intra-BLC infusions of the muscarinic receptor agonist oxotremorine (10 ng/0.2 microliter per side) or saline. On a 24 hr retention test each rat was placed in a "safe" arm of the maze and allowed to access all maze arms. Lidocaine-treated rats had impaired memory for the classical fear conditioning when they were compared with the saline-treated controls: they spent less time freezing, entered the shock arm more readily and more often, and spent more time in it. In contrast, oxotremorine-treated rats had a stronger memory for the context-footshock association as assessed by all measures of memory. Thus, post-training treatments affecting BLC function modulate memory for Pavlovian contextual fear conditioning in a manner similar to that found with other types of training.