ABSTRACT
The human 5-hydroxytryptamine (5-HT(4)) receptor is encoded by a highly complex gene which gives rise to at least 10 distinct splice variants. However, the functional relevance of these variants is unknown. In rat, only three such variants have been identified, 5-HT(4a) (r5-HT(4a)), 5-HT(4b) (r5-HT(4b)) and 5-HT(4e) (r5-HT(4e)). In the current study we identify and characterise the pharmacology of a novel rat splice variant (r5-HT(4c1)) and present the first comprehensive analysis of 5-HT(4) splice variant mRNA expression levels throughout the rat gastrointestinal tract. In addition, we describe preliminary characterisation of the first 5-HT(4) splice variant specific antibodies. In transfected cells, r5-HT(4c1) receptor exhibited similar binding properties to r5-HT(4a) and r5-HT(4b). Functional studies showed that 5-HT(4) agonists prucalopride (4-amino-5-chloro-2,3-dihydro-N-[1-(3-methoxypropyl)-4-piperidinyl]-7-benzofuran carboxamide monohydrochloride and renzapride (+/-)-endo-4-amino-5-chloro-2-methoxy-N-(1-azabicyclo[3.3.1]non-4-yl)benzamide monohydrochloride) acted as partial agonists at r5-HT(4c1), but full agonists at r5-HT(4a) and r5-HT(4b). Moreover, in contrast to r5-HT(4a) and r5-HT(4b), r5-HT(4c1) was not constitutively active. TaqMan mRNA analysis showed that r5-HT(4a) expression in brain and dorsal root ganglion exceeded that in the gastrointestinal tract, whilst the reverse was true for r5-HT(4b) and r5-HT(4c1). mRNA expression of each variant also increased distally throughout the gastrointestinal tract with the highest levels in the colon. r5-HT(4a) and r5-HT(4b) specific immunoreactivity was abundant on enteric neurons in jejunum, ileum and colon as well as neurons and satellite cells of the dorsal root ganglion. Only r5-HT(4b) immunoreactivity was observed on endocrine cells in the duodenum. These data could have implications in rat models and aid understanding of 5-HT(4) splice variant function.
Subject(s)
Alternative Splicing , Antibodies, Monoclonal/pharmacology , Receptors, Serotonin, 5-HT4/genetics , Animals , Antibodies, Monoclonal/immunology , Antibodies, Monoclonal/metabolism , Base Sequence , Binding, Competitive , Cell Line , Cell Membrane/metabolism , Cloning, Molecular , Cyclic AMP/metabolism , Female , Gastrointestinal Tract/metabolism , Humans , Immunohistochemistry , Male , Molecular Sequence Data , Protein Isoforms , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rabbits , Radioligand Assay , Rats , Rats, Sprague-Dawley , Receptors, Serotonin, 5-HT4/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Serotonin Receptor Agonists/pharmacology , TransfectionABSTRACT
Starting from a benzazepine sulfonamide 5-HT(6) receptor antagonist lead with limited brain penetration, application of a strategy of conformational constraint and reduction of hydrogen bond donor count led to a novel series of tricyclic derivatives with high 5-HT(6) receptor affinity and excellent brain:blood ratios.
Subject(s)
Antidepressive Agents, Tricyclic/chemical synthesis , Brain/drug effects , Chemistry, Pharmaceutical/methods , Receptors, Serotonin/chemistry , Serotonin Antagonists/chemical synthesis , Animals , Antidepressive Agents, Tricyclic/pharmacology , Blood-Brain Barrier/drug effects , Cytochrome P-450 CYP3A , Cytochrome P-450 Enzyme System/chemistry , Humans , Hydrogen Bonding , Microsomes/drug effects , Models, Chemical , Molecular Conformation , Protein Isoforms , Rats , Serotonin Antagonists/pharmacologyABSTRACT
Modification of the potent imidazole-based B-Raf inhibitor SB-590885 resulted in the identification of a series of furan-based derivatives with enhanced CNS penetration. One such compound, SB-699393 (17), was examined in vivo to challenge the hypothesis that selective B-Raf inhibitors may be of value in the treatment of stroke.
Subject(s)
Central Nervous System/drug effects , Furans/chemical synthesis , Furans/pharmacology , Indans/chemical synthesis , Indans/pharmacology , Proto-Oncogene Proteins B-raf/antagonists & inhibitors , Animals , Furans/chemistry , Imidazoles/chemistry , Imidazoles/pharmacology , Indans/chemistry , Molecular Structure , Pyridines/chemistry , Pyridines/pharmacology , Rats , Stroke/drug therapy , Structure-Activity RelationshipABSTRACT
Traditional birth attendants (TBAs) and village midwives have been employed in many interventions to reduce maternal mortality in developing countries. This study reviews the results of 15 TBA- and midwife-based interventions that aim to improve skilled assistance in delivery and recognition and referral of complications. Outcome measures used to evaluate the impact of the programmes varied. Five of the five programmes reviewed that evaluated their impact on maternal mortality demonstrated a decline in maternal mortality ratios, two of three studies measuring morbidity-related indicators found improvement of some but not all morbidity outcomes, six of seven showed a trend of improved referral rates, and three of three found high levels of knowledge retention among trained TBAs. Programmes with the greatest impact utilised TBAs and village midwives within multisectoral interventions. These findings suggest that TBAs and village midwives contribute to positive programme outcomes. Further investigation is needed to determine the nature of their contribution within larger programmes.
Subject(s)
Maternal Health Services/standards , Maternal Mortality/trends , Midwifery/education , Professional Competence , Adolescent , Adult , Developing Countries , Female , Humans , Maternal Health Services/trends , Maternal Welfare , Pregnancy , Program Evaluation , Risk Assessment , Survival AnalysisABSTRACT
Cell death mechanisms frequently involve the influx of extracellular calcium through voltage- and ligand-gated ion channels, e.g., the NMDA receptor (Greene, 1999). The vanilloid receptor (VR1) is present in regions of the brain (Mezey et al., 2000) that are highly susceptible to neurodegenerative insults, suggesting that this ion channel might contribute to the cellular processes involved in neuronal death. We tested the effects of VR1 ligands in the oxygen glucose deprivation (OGD) model of cell death in organotypic hippocampal slice cultures. The VR1 agonist capsaicin at concentrations that are selective for VR1 did not affect cell viability per se or the extent of neurodegeneration induced by the OGD insult. In contrast, the VR1 antagonist capsazepine (0.1-10 microm) significantly reduced the amount of OGD-induced cell death. However, capsazepine was still neuroprotective in slices prepared from VR1 knock-out mice, which exhibited the same degree of neurodegeneration to that observed in slices prepared from wild-type mice, excluding the possibility that it afforded neuroprotection through inhibition of VR1. Instead, capsazepine inhibited the hyperpolarization-activated nonspecific cation channel generated current I(h) in a concentration range similar to that which was neuroprotective. Furthermore, the specific I(h) blocker ZD-7288 was also neuroprotective, mirroring the effects of capsazepine, in that it was effective at preventing cell death when applied either during or after the OGD insult. These results demonstrate that capsazepine affords neuroprotection through inhibition of I(h) rather than inhibition of VR1.
Subject(s)
Capsaicin/analogs & derivatives , Capsaicin/pharmacology , Cell Hypoxia/physiology , Glucose/metabolism , Ion Channels/antagonists & inhibitors , Nerve Tissue Proteins , Neurons/drug effects , Neurons/metabolism , Animals , Cell Death , Cells, Cultured , Cyclic Nucleotide-Gated Cation Channels , Cytoprotection/drug effects , Cytoprotection/physiology , Dose-Response Relationship, Drug , Glucose/deficiency , Hippocampus/cytology , Hippocampus/drug effects , Hippocampus/metabolism , Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels , In Vitro Techniques , Ion Channels/metabolism , Mice , Mice, Knockout , Neuroprotective Agents/pharmacology , Patch-Clamp Techniques , Potassium Channels , Rats , Rats, Sprague-Dawley , Receptors, Drug/deficiency , Receptors, Drug/geneticsABSTRACT
Group I metabotropic glutamate receptors (mGluRs) cause increased neuronal excitability that can lead to epileptogenesis and neurodegeneration. Here we have examined how individual members of this subgroup of mGluRs affect synchronised hippocampal synaptic activity under normal and disinhibited conditions similar to those that occur during certain epileptic states. We demonstrate that activation of both mGluR1 and mGluR5 are important in increasing neuronal synaptic excitability by increasing synchrony between cells and driving correlated network activity in circuits that contain, or are devoid of, GABA(A) receptor-mediated synaptic inputs. The precise patterning of activity that occurs is complex and depends upon: (1) the existing pattern of ongoing network activity prior to mGluR activation; and (2) the relative extent of activation of each mGluR subtype. However, mGluR5 appears to be the principal mGluR subtype that initiates bursting activity irrespective of the inhibitory synaptic tone within the neuronal network.
