Analysis of dissociated single neurons by simple and semi-quantitative RT-PCR (reverse transcription and polymerase chain reaction)

Histamine Induces Alzheimer's Disease-Like Blood Brain Barrier Breach and Local Cellular Responses in Mouse Brain Organotypic Cultures

Among the top ten causes of death in the United States, Alzheimer's disease (AD) is the only one that cannot be cured, prevented, or even slowed down at present. Significant efforts have been exerted in generating model systems to delineate the mechanism as well as establishing platforms for drug screening. In this study, a promising candidate model utilizing primary mouse brain organotypic (MBO) cultures is reported. For the first time, we have demonstrated that the MBO cultures exhibit increased blood brain barrier (BBB) permeability as shown by IgG leakage into the brain parenchyma, astrocyte activation as evidenced by increased expression of glial fibrillary acidic protein (GFAP), and neuronal damage-response as suggested by increased vimentin-positive neurons occur upon histamine treatment. Identical responses-a breakdown of the BBB, astrocyte activation, and neuronal expression of vimentin-were then demonstrated in brains from AD patients compared to age-matched controls, consistent with other reports. Thus, the histamine-treated MBO culture system may provide a valuable tool in combating AD.

A qualitative look at multiplex gene expression of single cells using capillary electrophoresis

We demonstrate the first use of capillary electrophoresis with laser-induced fluorescence (CE-LIF) for the qualitative analysis of single-cell multiplex products of the reverse transcriptase-polymerase chain reaction (RT-PCR). The expression of both estrogen receptor alpha (ERalpha) and beta-actin in individual MCF-7 cells was monitored using a one-pot reaction. Reverse transcription and a single round of touch-down PCR, performed in a multiplex format, were used to generate fragment sizes of 318 bp and 838 bp, for ERalpha and beta-actin, respectively. A replaceable hydroxypropylmethylcellulose sieving matrix was used to effect a size-based separation of ethidium bromide-bound DNA. As titration of RT-PCR reaction components did not appreciably influence multiplex product generation, the use of additives, including bovine serum albumin (BSA) and herring sperm DNA, was explored. The addition of BSA to the RT-PCR mixture only resulted in efficient amplification of beta-actin, whereas the DNA carrier allowed co-amplification of both ERalpha and beta-actin. Furthermore, the sensitivity of our CE-LIF method eliminated the need for a second round of nested PCR, typically required when RT-PCR products are analyzed using gel electrophoresis.

Expression of BLT1 leukotriene B4 receptor on the dorsal root ganglion neurons in mice

We investigated using mice whether dorsal root ganglion (DRG) neurons express leukotriene B4 receptors. BLT1, but not BLT2, receptor mRNA was expressed in the DRG. Leukotriene B4 increased intracellular Ca2+ concentration in cultured DRG neurons, which was inhibited by leukotriene B4 antagonist. Many BLT1-immunoreactive neurons were small in size and positive for TRPV1. BLT1-immunoreactive fibers are present in the skin. The results suggest the expression of functional BLT1 receptors in the sensory neurons.

Inhibitory effect of histamine on axonal transport in cultured mouse dorsal root ganglion neurons

Histamine is important in mediating peripheral sensory information such as inflammation, allergic hypersensitivity, and itch. In the present study, using video-enhanced microscopy, we investigated the effect of histamine on axonal transport in cultured dorsal root ganglion (DRG) neurons of the mouse. Application of histamine (100 microM) reversibly reduced the number of particles transported within neurites in both anterograde and retrograde directions. The histamine H(1)-receptor agonist 2-thiazolylethylamine (100 microM) and the H(3)-receptor agonist R-alpha-methylhistamine (100 microM) also reduced anterograde and retrograde axonal transport, whereas the histamine H(2)-receptor agonist dimaprit (100-1000 microM) had no effect. The effect of histamine was partially blocked by pretreatment with H(1)-receptor antagonist pyrilamine (1 microM) or the H(3)-receptor antagonist thioperamide (1 microM). Pretreatment with a combination of pyrilamine (1 microM) and thioperamide (1 microM) completely blocked the response to histamine. The H(2)-receptor antagonist cimetidine (1 microM) was ineffective. These results suggest that histamine inhibits axonal transport of cultured mouse DRG neurons via the activation of H(1)- and H(3)-receptors.

Histamine sensitivity of mesenteric afferent nerves in the rat jejunum

The concept of functional interaction between mast cells and intestinal afferents is gaining support. We have therefore characterized the action of histamine on jejunal afferent discharge in the anesthetized rat. Whole nerve mesenteric afferent discharge was recorded in conjunction with intestinal pressure in response to a range of histamine agonists and antagonists. Histamine at 2, 4, and 8 micromol/kg (iv) evoked a dose-dependent biphasic increase in afferent discharge together with a biphasic rise in intestinal pressure. However, these two events were mediated independently, since nifedipine (1 mg/kg) substantially reduced the intestinal pressure increase but not the afferent discharge. These responses were completely inhibited by pyrilamine (5 mg/kg) but unaffected by ranitidine (5 mg/kg) or thioperamide (2 mg/kg). Neither the selective H2 receptor agonist dimaprit nor the selective H3 receptor agonist R-alpha-methylhistamine caused any modulation of afferent discharge. We conclude that histamine stimulates an H1 receptor-mediated increase in mesenteric afferent discharge that is independent of intestinal motor events. This suggests that histamine potentially acts as a mediator in mast cell-to-afferent nerve communication in the small intestine.