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It has been reported that GABA affects the regulation of cardiovascular function through both the peripheral GABAergic system and central GABAergic mechanisms. Intracerebral or intraventricular administration of GABA agonists or GABA transaminase inhibitors has been shown to lower blood pressure and heart rate via central GABAergic mechanisms [1, 4, 5, 16, 19, 25]. Intravenous administration of GABA was found to lower blood pressure and to induce bradycardia in dogs [6]. In this case, it is most likely that peripheral GABA actions were responsible for changes in cardiovascular funetion, since GABA is unable to cross the blood-brain barrier [11]. In in vitro experiments, GABA inhibited the stimulation evoked release of norepinephrine from the rat atria [2]. It has been proposed that GABA induces a release of noncholinergic and nonadrenergic substance [13]. However, evidence of the presence of GABAergic neurons in the heart has not been reported. The role of central GABAergic mechanisms in cardiovascular funetion has been reviewed in detail and is not addressed here. Of relevance to this chapter are those studies that implicate a peripheral cardiovascular function for GABA and a possible neurotransmitter role for GABA in the sinus node of the heart.

BACKGROUND: Intracellular proteases constitute a class of promising drug discovery targets. Methods for high throughput screening against these targets are generally limited to in vitro biochemical assays that can suffer many technical limitations, as well as failing to capture the biological context of proteases within the cellular pathways that lead to their activation. METHODS #ENTITYSTARTX00026; FINDINGS: We describe here a versatile system for reconstituting protease activation networks in yeast and assaying the activity of these pathways using a cleavable transcription factor substrate in conjunction with reporter gene read-outs. The utility of these versatile assay components and their application for screening strategies was validated for all ten human Caspases, a family of intracellular proteases involved in cell death and inflammation, including implementation of assays for high throughput screening (HTS) of chemical libraries and functional screening of cDNA libraries. The versatility of the technology was also demonstrated for human autophagins, cysteine proteases involved in autophagy. CONCLUSIONS: Altogether, the yeast-based systems described here for monitoring activity of ectopically expressed mammalian proteases provide a fascile platform for functional genomics and chemical library screening., PloS one, 4(10), e7655; 2009

Preparations of longitudinal muscle attached to myenteric plexus from guinea pig ileum were used to observe the effect of trimebutine on intestinal motility. Electrical stimulation at 0.2 Hz and 5 Hz produced contraction mediated by the release of acetylcholine in the preparations. The response to low-frequency stimulation (0.2 Hz) was inhibited by trimebutine (10(-8)-10(-5) mol/L), and the response to high-frequency stimulation (5 Hz) was enhanced by the drug at low concentrations (10(-8)-10(-7) mol/L) and inhibited by high concentrations (10(-6)-10(-5) mol/L). This enhancement was mimicked by [D-Ala2,N-Me-Phe4,Gly5-ol]enkephalin, and was antagonized by naloxone but not by MR2266. Enhancement by trimebutine was inhibited by yohimbine. Trimebutine (greater than or equal to 10(-8) mol/L) inhibited stimulation (5 Hz)-evoked release of norepinephrine, and the trimebutine effect was antagonized by naloxone but not by MR2266. Low concentrations of trimebutine inhibit norepinephrine release via the mu-opioid receptor and enhance intestinal motility by preventing the adrenergic inhibition of acetylcholine release. Inhibition by trimebutine was antagonized either by naloxone or MR2266. High concentrations of trimebutine may inhibit acetylcholine release via the mu- and kappa-opioid receptors, after which the intestinal motility is inhibited. Trimebutine at further high concentrations (greater than 10(-5) mol/L) contracted single smooth muscle cells from the circular muscle layers but not from the longitudinal muscle layers. The usual dose of trimebutine may exert dual effect on the intestinal motility indirectly through cholinergic and adrenergic neurons without direct effect on the smooth muscle.

The distribution of protein kinase C (PKC) subspecies and their colocalization with neurotransmitters were examined in the rat striatum and substantia nigra (SN), using immunocytochemistry. The alpha- and beta I-PKC immunoreactivies were seen predominantly in the perikarya of the neurons in the striatum and SN. In contrast, the beta II- and gamma- PKC immunoreactivities were abundant in both the perikarya and the neuropils in the striatum and only in the neuropils in the SN. From electron microscopic studies, the alpha- and beta I-PKC immunoreactivities were seen adjacent to the plasma membrane, while the beta II-PKC immunoreactivity was observed in the cytoplasm around the Golgi complex. The gamma-PKC immunoreaction was dense throughout the cytoplasm. The double-staining and lesion studies revealed that the alpha-PKC-immunopositive neurons in the striatum were intrinsic cholinergic neurons, and that most of the alpha-PKC-immunoreactive neurons in the SN were dopaminergic neurons. The beta I-PKC- immunoreactive neurons were intrinsic GABAergic neurons in the striatum. Moreover, most of the beta II- and gamma-PKC-immunoreactive neurons were medium-sized neurons projecting to the SN, and over 90% of GABAergic neurons in the caudate-putamen contained beta II-PKC. The beta II-PKC-immunoreactive neurons showed no gamma-PKC immunoreactivity, and the gamma-PKC-immunoreactive neurons were not beta II-PKC immunoreactive. These findings suggest that alpha-PKC is related to the function of the nigral dopaminergic and the striatal cholinergic neurons, and that the beta I-PKC is involved in the function of the striatal intrinsic GABAergic neurons. The beta II- and gamma-PKC may also modulate a specific neuronal function in the striatonigral system.

The γ-aminobutyric acid (GABA) receptors have been classified into two subtypes, termed GABAA and GABAB receptors, in the basis of their pharmacological properties (Bowery et al., 1984; 1989; Bormann, 1988). The GABAA receptor with its integrated Cl-channel is now well characterized. Studies revealed the amino acid sequence of the GABAA receptor (Schofield et al., 1987; Levitan et al., 1988). Stimulation of the GABAB receptor has been shown to induce two membrane effects, namely reduction in Ca2+ conductance and increase in K+ conductance (Bormann, 1988; Bowery, 1989), however, the GABAB receptor has not been purified. The expression of GABAB receptor in the Xenopus oocytes may provide information on molecular mechanisms of GABAB receptor-mediated responses.