Characterization of the mechanism of action of tachykinins in rat striatal cholinergic interneurons.

The mechanism by which substance P depolarizes cholinergic interneurons in the rat striatum was studied using whole-cell recording techniques. In all cases the effects of substance P were mimicked by the neurokinin1 receptor agonist [Sar9, Met(O2)11] substance P and were antagonized by the neurokinin1 receptor antagonist SR140333. [Sar9, Met(O2)11] substance P was found to depolarize cholinergic interneurons by the induction of a calcium-activated inward current at -60 mV. This inward current was irreversibly potentiated by photolysis of caged GTPgammaS within neurons implicating the involvement of a G-protein. The [Sar9, Met(O2)11] substance P-induced inward current was inhibited by the phospholipase C inhibitor U-73122, and by the inclusion of the inositol-1,4,5-triphosphate receptor antagonist heparin in the electrode solution. These findings suggest that neurokinin1 receptors depolarize cholinergic interneurons in the rat striatum primarily through a phosphoinositide signalling pathway.

Histamine depolarizes cholinergic interneurones in the rat striatum via a H(1)-receptor mediated action.

1. Whole-cell patch clamp recordings were made from rat striatal cholinergic interneurones in slices of brain tissue in vitro. Bath application of histamine (EC(50) 6.3 microM) was found to rapidly and reversibly depolarize these neurones through the induction of an inward current at -60 mV. 2. The effects of histamine were mimicked by the H(1) receptor agonist 2-thiazolylethylamine (50 microM) and selectively inhibited by pre-incubation with the H(1) receptor antagonist triprolidine (1 microM). 3. Ion substitution experiments under voltage clamp conditions revealed that the histamine activated current was comprised of two components. One component was sensitive to the concentration of extracellular Na(+), whilst the other component was inhibited by intracellular Cs(+) or extracellular Ba(2+). 4. In situ hybridization experiments revealed that the majority of cholinergic interneurones in the rat striatum express the histamine H(1) receptor but few neurones express H(2) receptors. These findings were confirmed using single cell RT - PCR. 5. It is concluded that histamine depolarizes cholinergic interneurones in the rat striatum via a H(1)-receptor mediated mechanism.

Single cell expression analysis--pharmacogenomic potential.

A fundamental challenge in biology is to correlate physiology with gene expression in specific cell types. This can only be achieved by understanding gene expression at the level of the single cell because, in many systems, each cell has the capacity to express a unique set of genes. Therefore, each cell can be considered to be functionally distinct. A clearer understanding of gene expression differences at such a discrete level provides an opportunity to develop drugs with more targeted pharmacologies or with decreased side effects.

Pulsed dye laser system for Raman and luminescence spectroscopy.

A spectroscopic system using a pulsed dye laser to measure Raman scattering and luminescence spectra in solids is described. The dye laser, which is pumped by a pulsed nitrogen laser, is capable of being continuously tuned throughout the visible and near ultraviolet regions of the spectrum. The detection system uses gated photon counting, synchronized to the laser pulses. The apparatus combines a greater tuning range than that obtained using cw dye lasers with enhanced sensitivity over pulsed systems using analogue detection.

The diagnostic and therapeutic impact of MRI: an observational multi-centre study.

AIM: To provide information about the diagnostic and therapeutic impact of magnetic resonance imaging (MRI) and to compare the findings across diagnostic groups. MATERIALS AND METHODS: A prospective, observational study of 2017 consecutive referrals for MRI of the head, spine or knee at four imaging centres. Clinicians completed questionnaires before MRI stating initial diagnoses, diagnostic confidence and treatment plans. After imaging, a second questionnaire evaluated clinicians' revised diagnosis and treatment plans in the light of imaging findings. Patients were grouped into nine diagnostic categories for analysis. Comparison between pre- and post-imaging was used to assess the diagnostic and therapeutic impact of MRI. RESULTS: In seven of nine diagnostic groups MRI findings were associated with a diagnostic impact. Diagnoses were revised or discarded following normal MR findings and diagnostic confidence was increased by confirmative MR findings. There was no statistically significant diagnostic impact for suspected pituitary or cerebello-pontine angle lesions. In five of nine diagnostic groups (knee meniscus, knee ligament, multiple sclerosis, lumbar and cervical spine) MRI findings had a clear impact on treatment plans. CONCLUSION: This study demonstrates that in most diagnostic categories, MRI influences diagnosis and treatment. However, experimental studies are needed to prove that these diagnostic and therapeutic impacts lead to improved health.Hollingworth (2000). Clinical Radiology55, 825-831.

Self reported health status and magnetic resonance imaging findings in patients with low back pain.

The authors present a prospective study of quality of life (SF-36) and MRI findings in patients with low back pain (LBP). Disc herniation and nerve root compression contribute to LBP and poor quality of life. However, significant proportions of asymptomatic subjects have disc herniation and neural compromise. Little is known about the influence of disc abnormalities and neural compression on quality of life in symptomatic patients. The purpose of this study was to assess the relationship between the extent of disc abnormality, neural impingement and quality of life. A total of 317 consecutive patients with LBP referred for MRI completed an SF-36 health status questionnaire immediately before imaging and again 6 months later. Patients were grouped according to the most extensive disc abnormality and any neural compromise reported at MRI. The relationship between symptoms, radiological signs and SF-36 scores was assessed. Eighty percent (255/317) and 65% (205/317) of patients completed the initial and 6-month SF-36, respectively. Thirty-six percent of patients (115/317) had one or more herniated discs and 44% (140/317) had neural impingement. There was little relationship between the extent of disc abnormality and quality of life. Patients with radiological evidence of neural impingement reported better general health (P < 0.01). SF-36 scores improved at 6 months in four dimensions, but general health deteriorated (P < 0.01). Patients with neural impingement had improved pain scores at 6 months (P < 0.05). The study results showed that the pain and dysfunction caused by disc herniation and neural compromise are not sufficiently distinct from other causes of back pain to be distinguished by the SF-36. Whilst neural compromise may be the best radiological feature distinguishing patients who may benefit from intervention, it cannot predict quality of life deficits in the diffuse group of patients with LBP.

Correlating physiology with gene expression in striatal cholinergic neurones.

The expression of 34 transmitter-related genes has been examined in the cholinergic neurones of rat striatal brain slices, with the aim of correlating gene expression with functional activity. The mRNAs encoding types I, II/IIA, and III alpha subunits of the voltage-sensitive sodium channels were detected, suggesting the presence of these three types of sodium channel. Similarly, mRNAs encoding all four alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-type glutamate receptor subunits and the NR1 and NR2A, 2B, and 2D subunits of the NMDA-type glutamate receptors were detected, suggesting that various combinations of these subunits mediate the cellular response to synaptically released glutamate. Other mRNAs detected included the NK1 and NK3 tachykinin receptors, all four known adenosine receptors, and the GABA-synthesising enzyme glutamate decarboxylase. Subpopulations of these cholinergic neurones have been identified on the basis of the expression of the NK3 tachykinin receptor in 5% and the trkC neurotrophin receptor in 12% of the cells investigated.