Changes in the Proportion of Inhibitory Interneuron Types from Sensory to Executive Areas of the Primate Neocortex: Implications for the Origins of Working Memory Representations.

Neuronal spiking activity encoding working memory (WM) is robust in primate association cortices but weak or absent in early sensory cortices. This may be linked to changes in the proportion of neuronal types across areas that influence circuits' ability to generate recurrent excitation. We recorded neuronal activity from areas middle temporal (MT), medial superior temporal (MST), and the lateral prefrontal cortex (LPFC) of monkeys performing a WM task and classified neurons as narrow (NS) and broad spiking (BS). The ratio NS/BS decreased from MT > MST > LPFC. We analyzed the Allen Institute database of ex vivo mice/human intracellular recordings to interpret our data. Our analysis suggests that NS neurons correspond to parvalbumin (PV) or somatostatin (SST) interneurons while BS neurons are pyramidal (P) cells or vasoactive intestinal peptide (VIP) interneurons. We labeled neurons in monkey tissue sections of MT/MST and LPFC and found that the proportion of PV in cortical layers 2/3 decreased, while the proportion of CR cells increased from MT/MST to LPFC. Assuming that primate CR/CB/PV cells perform similar computations as mice VIP/SST/PV cells, our results suggest that changes in the proportion of CR and PV neurons in layers 2/3 cells may favor the emergence of activity encoding WM in association areas.

CRF Mediates Stress-Induced Pathophysiological High-Frequency Oscillations in Traumatic Brain Injury.

It is not known why there is increased risk to have seizures with increased anxiety and stress after traumatic brain injury (TBI). Stressors cause the release of corticotropin-releasing factor (CRF) both from the hypothalamic pituitary adrenal (HPA) axis and from CNS neurons located in the central amygdala and GABAergic interneurons. We have previously shown that CRF signaling is plastic, becoming excitatory instead of inhibitory after the kindling model of epilepsy. Here, using Sprague Dawley rats we have found that CRF signaling increased excitability after TBI. Following TBI, CRF type 1 receptor (CRFR1)-mediated activity caused abnormally large electrical responses in the amygdala, including fast ripples, which are considered to be epileptogenic. After TBI, we also found the ripple (120-250 Hz) and fast ripple activity (>250 Hz) was cross-frequency coupled with θ (3-8 Hz) oscillations. CRFR1 antagonists reduced the incidence of phase coupling between ripples and fast ripples. Our observations indicate that pathophysiological signaling of the CRFR1 increases the incidence of epileptiform activity after TBI. The use for CRFR1 antagonist may be useful to reduce the severity and frequency of TBI associated epileptic seizures.

Identification of a novel synaptic protein, TMTC3, involved in periventricular nodular heterotopia with intellectual disability and epilepsy.

Defects in neuronal migration cause brain malformations, which are associated with intellectual disability (ID) and epilepsy. Using exome sequencing, we identified compound heterozygous variants (p.Arg71His and p. Leu729ThrfsTer6) in TMTC3, encoding transmembrane and tetratricopeptide repeat containing 3, in four siblings with nocturnal seizures and ID. Three of the four siblings have periventricular nodular heterotopia (PVNH), a common brain malformation caused by failure of neurons to migrate from the ventricular zone to the cortex. Expression analysis using patient-derived cells confirmed reduced TMTC3 transcript levels and loss of the TMTC3 protein compared to parental and control cells. As TMTC3 function is currently unexplored in the brain, we gathered support for a neurobiological role for TMTC3 by generating flies with post-mitotic neuron-specific knockdown of the highly conserved Drosophila melanogaster TMTC3 ortholog, CG4050/tmtc3. Neuron-specific knockdown of tmtc3 in flies resulted in increased susceptibility to induced seizures. Importantly, this phenotype was rescued by neuron-specific expression of human TMTC3, suggesting a role for TMTC3 in seizure biology. In addition, we observed co-localization of TMTC3 in the rat brain with vesicular GABA transporter (VGAT), a presynaptic marker for inhibitory synapses. TMTC3 is localized at VGAT positive pre-synaptic terminals and boutons in the rat hypothalamus and piriform cortex, suggesting a role for TMTC3 in the regulation of GABAergic inhibitory synapses. TMTC3 did not co-localize with Vglut2, a presynaptic marker for excitatory neurons. Our data identified TMTC3 as a synaptic protein that is involved in PVNH with ID and epilepsy, in addition to its previously described association with cobblestone lissencephaly.

A switch in G protein coupling for type 1 corticotropin-releasing factor receptors promotes excitability in epileptic brains.

Anxiety and stress increase the frequency of epileptic seizures. These behavioral states induce the secretion of corticotropin-releasing factor (CRF), a 40-amino acid neuropeptide neurotransmitter that coordinates many behavioral responses to stress in the central nervous system. In the piriform cortex, which is one of the most seizurogenic regions of the brain, CRF normally dampens excitability. By contrast, CRF increased the excitability of the piriform cortex in rats subjected to kindling, a model of temporal lobe epilepsy. In nonkindled rats, CRF activates its receptor, a G protein (heterotrimeric guanosine triphosphate-binding protein)-coupled receptor, and signals through a Gαq/11-mediated pathway. After seizure induction, CRF signaling occurred through a pathway involving Gαs This change in signaling was associated with reduced abundance of regulator of G protein signaling protein type 2 (RGS2), which has been reported to inhibit Gαs-dependent signaling. RGS2 knockout mice responded to CRF in a similar manner as epileptic rats. These observations indicate that seizures produce changes in neuronal signaling that can increase seizure occurrence by converting a beneficial stress response into an epileptic trigger.

Metalloproteinase inhibition prevents inhibitory synapse reorganization and seizure genesis.

The integrity and stability of interneurons in a cortical network are essential for proper network function. Loss of interneuron synaptic stability and precise organization can lead to disruptions in the excitation/inhibition balance, a characteristic of epilepsy. This study aimed to identify alterations to the GABAergic interneuron network in the piriform cortex (PC: a cortical area believed to be involved in the development of seizures) after kindling-induced seizures. Immunohistochemistry was used to mark perineuronal nets (PNNs: structures in the extracellular matrix that provide synaptic stability and restrict reorganization of inhibitory interneurons) and interneuron nerve terminals in control and kindled tissues. We found that PNNs were significantly decreased around parvalbumin-positive interneurons after the induction of experimental epilepsy. Additionally, we found layer-specific increases in GABA release sites originating from calbindin, calretinin, and parvalbumin interneurons, implying that there is a re-wiring of the interneuronal network. This increase in release sites was matched by an increase in GABAergic post-synaptic densities. We hypothesized that the breakdown of the PNN could be due to the activity of matrix metalloproteinases (MMP) and that the prevention of PNN breakdown may reduce the rewiring of interneuronal circuits and suppress seizures. To test this hypothesis we employed doxycycline, a broad spectrum MMP inhibitor, to stabilize PNNs in kindled rats. We found that doxycycline prevented PNN breakdown, re-organization of the inhibitory innervation, and seizure genesis. Our observations indicate that PNN degradation may be necessary for the development of seizures by facilitating interneuron plasticity and increased GABAergic activity.

The loss of interneuron functional diversity in the piriform cortex after induction of experimental epilepsy.

Interneuronal functional diversity is thought to be an important factor in the control of neural network oscillations in many brain regions. Specifically, interneuron action potential firing patterns are thought to modulate brain rhythms. In neurological disorders such as epilepsy where brain rhythms are significantly disturbed interneuron function is largely unexplored. Thus the purpose of this study was to examine the functional diversity of piriform cortex interneurons (PC; an area of the brain that easily supports seizures) before and after kindling-induced epilepsy. Using cluster analysis, we found five control firing behaviors. These groups were termed: non-adapting very high frequency (NAvHF), adapting high frequency (AHF), adapting low frequency (ALF), strongly adapting low frequency (sALF), and weakly adapting low frequency (wALF). A morphological analysis showed these spiking patterns were not associated with any specific interneuronal morphology although we found that most of the cells displaying NAvHF firing pattern were multipolar. After kindling about 40% of interneuronal firing pattern changed, and neither the NAvHF nor the wALF phenotypes were found. We also found that in multipolar interneurons a long-lasting potassium current was increased. A qPCR analysis indicated Kv1.6 subtype was up-regulated after kindling. An immunocytochemical analysis showed that Kv1.6 protein expression on parvalbumin (multipolar) interneurons increased by greater than 400%. We also examined whether these changes could be due to the selective death of a subset of interneurons but found that there was no change in cell number. These data show an important loss of the functional diversity of interneurons in the PC. Our data suggest that under pathophysiological condition interneurons are plastic resulting in the attenuation of high frequency network oscillations in favor of low frequency network activity. This may be an important new mechanism by which network synchrony is disturbed in epileptic seizures.

Identification of a transcription factor, BHLHB8, involved in mouse seminal vesicle epithelium differentiation and function.

The seminal vesicle is a male accessory sex organ that develops from segments of the Wolffian duct adjacent to the urogenital sinus. It produces most of the seminal plasma in both humans and rodents. To date, very few transcription factors have been linked to the development and differentiation of seminal vesicles. In this study, we have examined the role of basic helix-loop-helix (BHLH) B8 transcription factor expressed at high levels in the adult seminal vesicle and during seminal gland differentiation. Immunofluorescent studies indicate that BHLHB8 is expressed within the epithelial layer of the seminal layer of the seminal vesicle following branching morphogenesis but prior to full maturation of cell morphology and function. Analysis of mice that do not express BHLHB8 (Bhlhb8(-/-)) indicates no deficiency in the initial development of the seminal vesicle. However, morphological and ultrastructural analysis indicates disruption of the epithelial cellular architecture. The seminal vesicle epithelial layer of 2-mo-old Bhlhb8(-/-) mice shows extensive cellular degeneration based on the appearance of reduced microvilli, altered granule size, and dilated endoplasmic reticulum and Golgi apparatus. The seminal vesicle epithelial cells also degenerate prematurely, as evidenced by disruption of nuclear architecture and significant accumulations of autophagic bodies. These results identify BHLHB8 as a regulator in establishing and stabilizing the secreting epithelial cells of the seminal vesicle.

The paradoxical reliance on allopathic medicine and positivist science among skeptical audiences.

A number of studies have found an association between what people see, hear and read in the mass media and their corresponding actions and beliefs. This link has been demonstrated both at the micro and at the macro levels of analysis. However, when people are asked directly about the impact of mass media they tend to deny that they are personally affected. In fact, they tend to describe themselves as critical and skeptical media consumers. The purpose of this paper is to explore this contradiction through 12 in-depth focus group discussions undertaken in Ontario, Canada in 2004. Findings from the focus group interviews confirm earlier research in that people claimed that they were not susceptible to media influence. At the same time as they said that they took information from the mass media "with a grain of salt", they articulated sophisticated and nuanced accounts of how and why they evaluated some information as good and some as bad. In general they evaluated media stories on the basis of the values of allopathic medicine and positivistic science. Moreover, in the context of the focus groups and their explicit comments on their skepticism, they discussed health information from the magazine articles that they were given to read (on either HIV/AIDS, Alzheimer's disease, or a heart disease). Possible explanations for these paradoxical findings are discussed.

Cancer in the mass print media: fear, uncertainty and the medical model.

Cancer is increasing in incidence and prevalence in North America and around the world. The mass print media play an important role in information provision about prevention, diagnosis and treatment of this disease, as well as informing health policy and personal experience. This paper reports on a content analysis of the portrayal of cancer in the highest circulating magazines available in Canada and published in Canada or the USA in 1991, 1996, 2001. It includes both manifest and latent analysis of the framing and content of cancer stories. Manifest analysis documented the dominance of the medical as compared to the lifestyle and political economy frames and the predominance of articles on breast as compared to other cancers. Latent themes included: an emphasis on fear of cancer in that: (1) cancer and fear are frequently conflated; cancer is said to grow outside of awareness; cancer is portrayed as (almost) inevitable; cancer is associated with normal experiences; early detection is associated with diagnosis; and scary statistics are emphasized; (2) contradictions and confusion exist within and between articles; and (3) metaphors of war and battle are used frequently. The paper concludes with a discussion of the implications of the linking of fear with cancer in the context of medicine as the solution.

Alteration in CD45RBhi/CD45RBlo T-cell ratio following CD45RB monoclonal-antibody therapy occurs by selective deletion of CD45RBhi effector cells.

Tolerance induction by CD45RB monoclonal antibody (mAb) in murine allograft models is associated with an alteration in the CD45RBlo/CD45RBhi T-cell ratio in favor of CD45RBlo T cells, which can function as regulatory cells and promote tolerance. It has been proposed that inversion of the CD45RBhi/CD45RBlo normal T-cell ratio by mAb can occur by down-regulation of CD45RB surface molecules expressed by T cells. Because CD45RB mAb infusion can lead to a reduction in peripheral T cells, we tested whether other mechanisms might participate in the inversion of the CD45RBhi/CD45RBlo ratio, including apoptosis of CD45RBhi cells. We report that CD45RB mAb led to rapid elimination of both CD4+ and CD8+ T cells in vitro. Importantly, CD45RB mAb selectively eliminated CD45RBhi T cells without affecting the viability of CD45RBlo T cells. Furthermore, the death of T cells occurred with a reduction in mitochondrial transmembrane potential and DNA fragmentation but with little evidence of nuclear condensation and cell shrinkage typically found with cells undergoing apoptosis. We propose that CD45RB mAb therapy may promote a dominant regulatory T-cell population that has the capacity to inhibit rejection by the selective elimination of CD45RBhi effector T cells. This occurs by a process that does not involve the classic morphologic features of apoptosis. Strategies that facilitate an inversion of the CD45RBhi/CD45RBlo T-cell subset ratio may improve the efficacy of CD45RB mAb, and therapeutic measures that prevent deletion of CD45RBhi T cells may need to be avoided to achieve tolerance clinically.