Essential hypertension is a highly hereditable trait of complex aetiology, where multiple environmental and life style factors contribute to blood pressure variation. Family health studies of blood pressure suggest that heritability accounts for 30 – 50 % of variation. Consequently the study of genetic architecture has proven useful to detect a small number of genes, loci, and single nucleotide polymorphisms (SNPs) that have appreciable effects on blood pressure. Genetic linkage and association methods have long provided the foundation of gene identification in humans. Although linkage studies have proven to be highly successful in identifying genes of monogenic (or Mendelian) disorders, this analysis has minimal or limited power to detect gene of complex traits and disease. Furthermore, candidate gene approaches have not yet reported any reproducible associations with hypertension. Accordingly, gene identification efforts have become increasingly reliant on association approaches. A recent genome wide association study (GWAS) identified a locus upstream of the Uromodulin (UMOD) gene transcriptional start site, which was associated with hypertension. This group used an extreme case - control design in a discovery sample of 1,621 hypertension cases and 1,699 hypercontrols, representing the top 2% and bottom 20% of the BP distribution. The minor G allele of rs13333226 when adjusted for estimated glomerular filtration rate (eGFR) was associated with a 7 % lower risk of developing hypertension. UMOD encodes the protein uromodulin which is interchangeably known as Tamm Horsfall protein (THP). It is a kidney specific protein and is exclusively synthesised at the level of the thick ascending limb of the loop of Henle (TAL) and is the most abundant protein in human urine. The biological role of uromodulin still remains unclear; however other UMOD variants have been associated with chronic kidney disease. Due to UMODs exclusive expression at the kidney it may have a role in regulating blood pressure via sodium homeostasis mechanisms. As hypertension is characterised by a disturbance of renal function that subsequently leads to an augmented Na+ reabsorption, the present study aimed to follow up the GWAS signal to assess whether altered 18 UMOD expression and/or function impacts on sodium homeostasis and influence blood pressure phenotypes. Promoter activity assays here demonstrate that the index SNP (rs13333226) is not a functional variant causing altered transcription, however the minor G allele of rs13333226 is associated with reduced promoter activity. These findings are consistent with the original GWAS study that this allele is associated with lower risk of hypertension. In this study we reported a SNP in LD with rs13333226 within the 2 Kb promoter region (rs4997081) that may be a causal variant altering transcriptional activity of UMOD. Furthermore, with computational and experimental evidence we show that binding of rs4997081 to TFAP2A in a genotype dependent manner leads to transcriptional changes of UMOD which were associated with altered sodium reabsorption via downstream signalling of Tumor necrosis factor alpha (TNF-α). Cardiovascular characterisation of UMOD knockout mice (KO) revealed significantly lower systolic blood pressure (SBP) in comparison to the wild type (WT) counterparts. The reported novel blood pressure phenotypes in the KO mice were not sensitive to change by salt loading (2% NaCl) over a six week period. KO mice displayed increased concentrations of sodium in the urine upon salt loading, to greater levels than the WT mice (± 2% NaCl). Urinary electrolyte analysis corrected to creatinine levels revealed augmented sodium loss in the KO mice during the high salt diet. Chronic renal function curves demonstrate that the reduced SBP is attained by increased natriuresis via augmented GFR in the KO mice. Histological examination illustrated cellular swelling and papillary oedema in the KO mice before and after salt loading which may be triggered by the pro-inflammatory cytokines TNF-α and Interleukin 1 (IL-1) according to metabolomic analysis. These inflammatory signals may affect Na+ homeostasis at the TAL in the KO mice by reducing NKCC2 expression. Expression analysis studied in outer medulla tissue illustrated down regulation of the major NaCl transporters in the absence of UMOD which were further attenuated upon salt loading conditions possibly by increased levels of TNF-α at the TAL. KO mice displayed increased levels of urinary TNF-α in addition to augmented mRNA abundance in the outer medulla tissue. In addition, immunohistochemical analysis revealed reduced NKCC2 staining with increased TNF-α staining in renal tissue of the KO mice during normal and high salt diets. These results were 19 confirmed in vitro and suggest UMOD acts as a negative regulator of TNF-α production by the TAL to maintain NaCl/volume homeostasis. We have confirmed with a small pilot study using human renal tissue samples from normotensive and hypertensive individuals, that in times of altered UMOD expression there are changes in NKCC2 and NHE3 expression levels, but not TNF- α. More interestingly we have demonstrated that UMOD, NKCC2, and NHE3 expression levels are altered in a genotype dependant manner, in that the minor G allele of rs13333226 appears to be associated with blood pressure via altered sodium homeostasis.

Drosophila is a valuable experimental organism can be used as a reverse genetics model. Drosophila Malpighian (renal) tubules are important epithelial tissue in which to study transport mechanisms. RNA-seq has been chosen to investigate Drosophila Malpighian (renal) tubules to identify novel genes following a three- way comparison between three popular transcriptome profiling methods. Two types of novel gene have been found in Drosophila tubules, coding genes and noncoding genes. Reverse genetics has been applied to identify novel coding gene function in Drosophila tubules. Three-way analysis of Drosophila expression microarrays, Drosophila tiling micrarrays and Drosophila RNA-seq reveal that most gene expression levels are well correlated between the three technologies. Drosophila expression microarrays and RNA-seq are correlated better than the correlation between Drosophila tiling microarrays and RNA-seq. Drosophila expression arrays and Drosophila tiling arrays all suffered from cross-hybridization, miss target detection and hybridization background noise, and also have low dynamic range for detecting lowly and highly expressed genes. Drosophila tiling microarrays also have a high false-positive detection rate, which may lead to overestimate the transcriptional activities of the genome. RNA-seq has overcome the drawbacks of microarrays and become the leading technology for genome sequencing, transcriptome profiling, novel gene discovery, and novel alternative splicing discovery with wide dynamic range. However, Drosophila expression microarrays and tiling microarrays still remain useful. Three-prime expression microarrays offer a means to measure the differential three-prime end processing, and tiling microarrays can be used for novel gene discovery. In this sense, the three technologies complement each other. Poly(A) selected RNA-seq has been used as a discovery tool for searching novel genes in Drosophila Malpighian tubules in this thesis. A TopHat and Cufflinks pipeline has been used as an analytical pipeline for novel gene discovery and differential gene expression analysis between Drosophila tubules and whole flies in order to find the tubule-enriched genes. Reverse genetics has been applied to Drosophila to achieve a gene knockdown and overexpression by using the unique Gal4/UAS system to achieve the novel gene knockdown or overexpression in specific tissue and cell types. Novel coding gene CG43968 has been discovered. The location of this gene has been confirmed in tubule main segments, principle cell cytoplasm or apical membrane. The function of this gene has been identified as involvement in tubule secretion, which may relate to calcium transport. Reverse genetics has been confirmed as particularly important for the functional study of novel genes.

Introduction: There is a hypothesis that Eye-Hand Coordination (EHC) is a general ability presenting an opportunity to explore it’s mechanisms via a series of innovative studies. The thesis outlines two major aims: 1) to establish reliable measurement techniques and protocols for EHC using the Sport Vision Trainer (SVT™); 2) to explore different training methods to understand if performance can be improved. Methods: Four hundred and seventy-six participants volunteered for the studies, predominately recruited from the undergraduate population of the sport and exercise science degree at Edge Hill University, apart from the final training study of a local table tennis team. A total of 23,112 trials were recorded in the technical evaluation using the SVT™. Three measurement studies were conducted to establish test-retest reliability, performance predictors, and effect of sporting experience. In addition, three training studies were completed investigating performance under different illumination levels, stroboscopic training, and a general vision training (GVT) programmes. Results: Reliable measurement protocols are reported for the SVT™ along with original insight into the effects on EHC performance. Discussion: The concept of EHC as a general ability in the sense of an overall element supporting performance on a range of associated tasks is explored. As the sport vision literature identifies a requirement to isolate individual components of visual software the final study gives unique insight into the effectiveness of a GVT programme focusing on EHC with a team of club table tennis players. Specific training implications, limitations and recommendations for further research are also presented. Conclusions: The existence of an inherent EHC ability is doubtful and whilst the usefulness of GVT programmes has been criticised, the focus on EHC as an isolated visuo-motor skill yielded both EHC improvement and performance gains in a sporting context.

The objective was to explore the role of GPR41 (FFAR3) and GPR43 (FFAR2) in colonic physiology and potential involvement in appetite control. The expression of SCFA receptors mRNA across the longitudinal axis of healthy mice, pig and human colon were found to be similar. Immunohistochemistry revealed FFAR2 and FFAR3 to be localised to flask shaped cells deep in colonic crypts and were identified as open type enteroendocrine cells by co-localisation with chromogranin A, a classical marker of enteroendocrine cells using both pig and human colon tissue. Further co-localisation studies with pig colonic tissue showed the SCFA receptors are co-localised with serotonin (enterochromaffin cells), and the satiety peptides, peptide YY (PYY) and glucagon like peptide 1 (GLP-1), indicative of enteroendocrine L cells. Impact of dietary fibre was assessed using colonic tissue collected from pigs fed a fermentable carbohydrate diet were compared to a control diet of less fermentable carbohydrate. Results demonstrate steady state SCFA concentrations exist in the colonic lumen, explained by enhanced uptake of SCFA due to an increased expression of SCFA transporter (MCT1). Dietary fibre was found to have minimal impact on relative abundance of the SCFA receptors mRNA across the longitudinal axis of pig colon. However, evaluation of the satiety peptides, PYY and pro-glucagon (precursor of GLP-1) mRNA have revealed a statistical significant increase in PYY but not pro-glucagon mRNA. Subsequently, attention was focused toward use of in-vitro models to explore SCFA receptors in appetite control. Initial in-vitro experiments assessed activity profile of SCFA receptors and evaluated chemical tools used to differentiate between FFAR2 and FFAR3. Murine ‘GLUTag’ and human ‘NCI-H716’ in-vitro models of enteroendocrine ‘L cells’ were characterised and SCFA induced GLP-1 secretion evaluated. 10mM butyrate and 10μM 4-CMTB induced GLP-1 release. RNA interference was used in attempt to knockdown FFAR2 in NCI-H716 cells to evaluate SCFA sensor’s involvement in GLP-1 release. In summary, luminal SCFA may stimulate SCFA receptors of enteroendocrine cells releasing peptides; GLP-1, PYY or serotonin to co-ordinate gut motility and appetite.

Molecular mechanisms governing the plasticity of cellular boundaries in confluent epithelial monolayers are poorly characterised. In this thesis, we report a drastic reorganisation of cellular boundaries, provoked by the prolonged withdrawal of EGF from non-malignant mammary epithelial cells, MCF10A and HMT-3522 cells. EGF withdrawal induces actin-rich interdigitations that protrude into neighbouring cells and are enriched in desmosomes. These protrusions allow the cellular sheets to resist mechanical and osmotic perturbation. Mobility of the cells within monolayers is also restricted. Overexpression of constitutively active Rac opposes interdigitations and induces membrane ruffling. EGF application reverses the interdigitations rapidly in a process that requires actin polymerisation and actomyosin contraction. We report here a simple in vitro system that can be utilised as a visual readout to dissect novel signaling pathways specific to EGFR activation and mammary morphogenesis. This thesis focuses on the initial efforts to characterise this dramatic remodeling of cellular boundaries and will discuss the potential investigations that can be pursued further hereon.

Pressurised situations have the potential to influence the performance of visual-motor tasks. The aim of this thesis was to investigate psychomotor mechanisms that may be responsible for such performance changes. A series of experimental studies were conducted in order to examine kinematic (Chapter 2) and attentional (Chapters 3 - 5) mechanisms. Performance pressure was successfully manipulated in all studies but performance was consistently maintained at a group-level. In the first experiment, individual differences in performance responses to pressure were found to correlate with kinematic changes, with decreases in movement amplitudes correlating with poorer performances. In the second experiment, pressure led to attentional narrowing as indicated by impaired performance of a useful field of view task. Pressure-induced changes in useful field of view correlated with performance changes. The third and fourth experiments demonstrated that pressure-induced changes in cognitive anxiety positively correlated with changes in the randomness of gaze behavior, which suggested that pressure has the potential to impact attentional control.

Ubiquitylation is a post-translational modification of proteins with a broad range of downstream effects, ranging from protein turnover to transcriptional regulation, membrane trafficking and DNA damage repair. The conjugation of ubiquitin to its substrate is a sequential process mediated by three enzymes, termed the E1 ubiquitin-activating enzyme, the E2 ubiquitin-conjugating enzyme and the E3 ubiquitin ligase. Conversely, the removal of ubiquitin is mediated by deubiquitylases (DUBs). My project aims to identify DUBs that are involved in the selective removal of mitochondria via autophagy (mitophagy), a process that is regulated by a serine/threonine kinase, PINK1, and an E3 ligase, Parkin. Loss-of-function mutations in both PINK1 and Parkin have been reported to cause autosomal recessive-juvenile Parkinsonism (AR-JP), a form of early onset Parkinson’s Disease (PD). During mitochondrial depolarisation, PINK1 is stabilized at the outer mitochondrial membrane (OMM) where it recruits and activates Parkin. Subsequently, Parkin ubiquitylates a range of OMM proteins either for their proteasomal degradation or for the recruitment of the autophagic machinery. I first characterised this process in two different cell lines expressing either low endogenous levels of Parkin (SH-SY5Y neuroblastoma cells) or high exogenous levels of YFP-Parkin (hTERT-RPE1-YFP-Parkin, retinal pigment epithelial cells). I developed two different assays to assess Parkin-mediated mitophagy: (1) real time monitoring of YFP-Parkin by live-cell imaging (only in hTERT-RPE1-YFP-Parkin cells), and (2) western blot analysis of the cleavage, ubiquitylation and loss of proteins during mitophagy (in both hTERT-RPE1-YFP-Parkin and SH-SY5Y cells). I used these two assays to perform siRNA screens to identify DUBs, for which depletion resulted in altered Parkin recruitment and/or ubiquitylation and degradation of Parkin substrates. I identified several DUBs, including USP10, USP30, USP38, USP42, USP43, USP49, BAP1, OTUD4 and TRABID, for which siRNA depletion resulted in delayed Parkin recruitment to the mitochondria. Further characterisation of the effects of USP42 and USP43 siRNA depletions suggests that the loss of these DUBs could either desensitize the cells or affect the cellular response towards mitochondrial depolarisation. Depletion of another DUB, USP31, partially inhibited the later stages of mitophagy, i.e. the degradation of mitochondria via the lysosomal pathway. I discovered by chance that high expression levels of Parkin resulted in a small percentage of mitophagic cell death that was dependent on both PINK1 and Parkin. This cell death was prevented or delayed by inhibiting the proteasome. Interestingly, depletion of USP30 exacerbated this mitophagic cell death. This effect of USP30 depletion is of particular interest as USP30 is the only mitochondria-localised DUB. Further characterisation revealed that USP30 opposes TOM20 ubiquitylation and degradation, a previously described Parkin substrate. I speculate that USP30 counteracts disproportionate Parkin-dependent ubiquitylation and proteasomal degradation of outer mitochondrial membrane proteins, and its depletion enhances apoptosis by promoting Cytochome-C release from damaged mitochondria. Importantly, USP30 depletion also enhances apoptosis induced by BH3-mimetics ABT-737 and ABT-263, suggesting a more general role for USP30 in determining the threshold for mitochondrial cell death. As USP30 depletion enhances the degradation of Parkin substrate and sensitize cells to apoptosis, this data suggest that USP30 is a potential drug target not only in Parkinson’s Disease but also in cancer.

The diphenylalanine (FF) dipeptide is the core recognition motif of the Alzheimer’s amyloid beta (Aß) polypeptide, as well as being important in other amyloidogenic proteins. The Aß polypeptide self assembles to form fibrils and these fibrils are found in the brains of patients with Alzheimer’s disease. FF itself is also known to self-assemble to form fibres and there has been much interest in the FF motif since Reches and Gazit made this observation. The structures it forms are biocompatible and have a high aspect ratio. Under different conditions of humidity and concentration it can form various morphologies such as nanovesicles and ribbons. Despite the great interest in this area, the self-assembly mechanism of these fibres is not known. The motivation throughout this work has been to understand the assembly of the elongated FF fibres in order to be able to control it for the variety of applications that have been suggested. Several experimental and theoretical techniques were used to this end. Molecular and metadynamics simulations were employed to investigate the early stages of the fibres assembly. Optical spectrocopy was used to investigate their assembly kinetics and mechanism in situ. New linear dichroism (LD) methods were developed in order to study the FF fibres which grow into large rigid structures. A new electronic LD sequencer was created which made it possible to automate kinetics measurements over long periods of time, and a new capillary was designed and built which could be cleaned more thoroughly than the previous models. These experiments showed that FF fibres assemble by nucleation driven assembly, with secondary nucleation taking place. They also showed that 40 °C is an important temperature in the onset of fibre formation. Electron and optical microscopy were used to quantify the heterogeneity of the fibres and to observe their growth in real time. It was found that the fibres were more heterogenous than had previously been reported. The results of these experiments elucidated new information about the characteristics and the self-assembly of FF fibres, as well as developed techniques in order to probe them, and similar biological fibres, further.

Human perception and cognition processing are not universal. Culture and experience markedly modulate visual information sampling in humans. Cross-cultural studies comparing between Western Caucasians (WCs) and East Asians (EAs) have shown cultural differences in behaviour and neural activities in regarding to perception and cognition. Particularly, a number of studies suggest a local perceptual bias for Westerners (WCs) and a global bias for Easterners (EAs): WCs perceive most efficiently the salient information in the focal object; as a contrast EAs are biased toward the information in the background. Such visual processing bias has been observed in a wide range of tasks and stimuli. However, the underlying neural mechanisms of such perceptual tunings, especially the temporal dynamic of different information coding, have yet to be clarified. Here, in the first two experiments I focus on the perceptual function of the diverse eye movement strategies between WCs and EAs. Human observers engage in different eye movement strategies to gather facial information: WCs preferentially fixate on the eyes and mouth, whereas EAs allocate their gaze relatively more on the center of the face. By employing a fixational eye movement paradigm in Study 1 and electroencephalographic (EEG) recording in study 2, the results confirm the cultural differences in spatial-frequency information tuning and suggest the different perceptual functions of preferred eye movement pattern as a function of culture. The third study makes use of EEG adaptation and hierarchical visual stimulus to access the cultural tuning in global/local processing. Culture diversity driven by selective attention is revealed in the early sensory stage. The results here together showed the temporal dynamic of cultural perceptual diversity. Cultural distinctions in the early time course are driven by selective attention to global information in EAs, whereas late effects are modulated by detail processing of local information in WC observers.

The experiments presented in this thesis describe the roles of the post-junctional α1, α2-adrenoceptors (AR) and P2X purinoceptors in response to sympathetic nerve stimulation in mouse mesenteric and tail arteries. Such roles were determined by combining wire myography techniques and nerve stimulation alongside various selective antagonists. The influence of each receptor on the response to nerve stimulation was first defined in wild type (WT) mice before analysis of α1-AR knock out (KO) mice. Therefore the effect that genetic removal of the α1-ARs had on vascular response could be investigated. The response is the force generated in milligrams/tension when the nerves are stimulated and correspond to activation of post-junctional receptors and subsequent smooth muscle cell contraction. Systolic Blood Pressure and the α1-ARs The aim of the first study (Chapter Three) was to determine whether systolic blood pressure (BP) was different in the KO mice compared to WT controls. Tail cuff measurements of systolic BP were recorded in WT and AR KO mice. It was found that BP was not affected by loss of the α1A- and α1D¬-AR subtypes (ADKO) or by loss of all three α1-AR subtypes (α1-null). Therefore, the α1-AR role in maintaining BP may not be as crucial as previously understood or, the remaining receptors may have compensated for the loss. Calcitonin Gene Related Peptide (CGRP) in Mouse mesenteric and tail arteries The second study (Chapter Four) examined whether, under the stimulation parameters used, the potent vasodilator CGRP masked the vasoconstrictor response to nerve stimulation in mouse mesenteric and tail arteries. The potent neurotoxin capsaicin depletes the sensory nerves of CGRP. Responses prior to capsaicin incubation were compared with those following capsaicin treatment in WT, ADKO and α1-null mice. In mesenteric artery from each mouse strain, capsaicin incubation had no significant effect on the peak response to nerve stimulation. Furthermore, in the tail artery, capsaicin treatment had no significant effects on the responses in WT and α1-null mice. However, in the ADKO mouse tail artery preparations, capsaicin treatment significantly increased the peak response at low frequency stimulation. These findings may indicate an interaction between the α1-AR subtypes and the release of CGRP whereby the presence of all or none of the subtypes (WT and α1-null) has no effect on CGRP release but loss of the α1A- and α1D-AR subtypes alters the balance and reveals a CGRP induced effect. Response to perivascular nerve stimulation in Mouse mesenteric and tail arteries from Wild Type mice The aim of Chapter Five was to determine which receptors were involved in the response to nerve stimulation in mouse mesenteric and tail arteries. These results would then act as a comparison with the ADKO and α1-null responses in the later chapters. A contractile response to nerve stimulation was recorded in each of the studied vessels and abolished by combined blocked with antagonists for the α1-, α2¬-ARs and P2X receptors. Individual receptor blockade and component analysis then revealed the roles of the individual receptors. In the mesenteric arteries, the α1-ARs were the main contributors to the response followed by the P2X receptors and finally the α2-ARs which displayed both pre- and post-junctional effects. No interactions were discovered between the α1-ARs and the other receptors. The P2X receptors initiated the contraction and prolonged the response at the low frequency and contributed to the contractile response at the high frequency. In the tail artery, the α2-ARs were the dominant receptors but required the presence of the α1-ARs, and to some extent the P2X receptors in order to produce a full contractile response upon activation. The P2X receptors alone initiated the response at low frequency stimulation with both α1-ARs and P2X receptors involved in initiation of the contraction at the high frequency. Response to perivascular nerve stimulation in mesenteric and tail arteries from mice lacking α1A- and α1D-AR subtypes (ADKO) Chapter Six determined the role of the α1B-ARs in the response to nerve stimulation and therefore examined whether loss of the α1A- and α1D-AR subtypes (ADKO) affected the response. In the mesenteric arteries, at the low frequency, there was a potential interaction between the receptors. However, no single receptor was responsible for the contraction although there was a trend for the P2X receptors to be active at the beginning of the response and the α2-ARs to be active at the latter stage of the response. This was also true at the higher frequency. The ADKO vessels displayed no evidence of pre-junctional α2-ARs. In the mesenteric arteries, there is little role for the α1B-ARs. The overall contribution in the tail artery was reduced in the ADKO, particularly at the higher frequency. Similar to the WT mice, the α2-ARs were the main contributor to the response. The P2X receptors initiated the contraction but required the α2-ARs to be active at the low frequency. The α1B-ARs also required an interaction with the other receptors at low frequency stimulation in order to contribute to the initiation of the response. The α1B-ARs also contributed to the initiation of the response at the high frequency without requiring the presence of the other receptors. Response to perivascular nerve stimulation in mesenteric and tail arteries from mice lacking α1A-, α1B- and α1D-AR subtypes (α1-null) In the final study (Chapter Seven), α1-null mice were utilised in order to determine whether loss of the α1-ARs had a significant effect on the response to nerve stimulation in mouse mesenteric and tail arteries. Furthermore, the influence of the α2-ARs and P2X receptors were compared with the response in the WT vessels to determine whether they compensate for the loss of the α1-ARs. The removal of the α1-ARs dramatically reduced the response to nerve stimulation in the mesenteric arteries, with no apparent compensation from the α2-ARs or P2X receptors. There was no evidence of pre-junctional α2-ARs. The small response recorded at the high frequency was initiated by the P2X receptors and maintained by the α2-ARs and P2X receptors. The tail artery response was smaller in the α1-null mice compared with WT, particularly at the higher frequency. However, the response was still mediated largely by the α2-ARs with an interaction with the P2X receptors likely. A potential compensatory mechanism was recorded at the lower frequency as the response to P2X receptor antagonism was greater in the α1-null than in the WT mice. As was shown in the WT, activation of the P2X receptors initiated the contraction, particularly at the high frequency. Findings and Results Collectively, the findings of the studies presented in this thesis demonstrate that the α1-, α2-ARs and P2X receptors are involved in the response to nerve stimulation in the mouse mesenteric and tail arteries. Genetic removal of the α1-ARs in the ADKO and α1-null is most effective in the mesenteric arteries with little evidence of any compensatory mechanisms. In the mouse tail artery, the α2-ARs are the main contributors to the response and so loss of the α1-ARs has less of an effect. Interactions between the receptors were most clearly shown in the tail artery with little interaction between the α1-ARs and the other receptors demonstrated in the mesentery. Furthermore, it has been demonstrated here that systolic BP is unaffected in the KO mice and there is little input from the CGRP nerves using the parameters tested. From these results, the importance of α1-AR activation in nerve mediated responses was determined. The absence of a compensatory mechanism to match the response lost in the ADKO and α1-null mice, and the presentation of a normal BP alongside the survival of these transgenic mice challenges the importance of the α1-ARs being crucial in the maintenance of vascular tone. This therefore complements the knowledge that treatment of primary hypertension with α1-AR antagonists is largely unsuccessful. The contractile response mediated by α2-ARs and P2X receptors may be used as potential therapeutic targets in controlling hypertension.