A Novel Ionic Current Contributing To Spasm Of Small Blood Vessels
Funder
National Health and Medical Research Council
Funding Amount
$287,500.00
Summary
Vascular smooth muscle can produce strong constrictions or spasms that can severely limit blood flow. Disorders arising from such spasms include sudden death, neurological deficits, visual and hearing loss or impairment, Raynaud's phenomenon (painful episodic contraction of the fingers and toes) and intestinal necrosis. Common mechanisms are likely to underlie the spasms associated with these disparate disorders. In a recent electrophysiological study of vascular smooth muscle, we discovered a n ....Vascular smooth muscle can produce strong constrictions or spasms that can severely limit blood flow. Disorders arising from such spasms include sudden death, neurological deficits, visual and hearing loss or impairment, Raynaud's phenomenon (painful episodic contraction of the fingers and toes) and intestinal necrosis. Common mechanisms are likely to underlie the spasms associated with these disparate disorders. In a recent electrophysiological study of vascular smooth muscle, we discovered a novel membrane current which we refer to as the plateau current. This current has a strong depolarizing influence that is likely to make a major contribution to the spasms, particularly in arterioles and small arteries which are more dependent on depolarization for contraction. Block of this current is expected to minimize the depolarization and therefore prevent or ameliorate spasm of the vessels. Thus the plateau current represents a new field of therapeutic potential for addressing vascular problems that have significant health implications. However, therapeutic manipulation of the current requires knowledge of its properties. In this project we will determine the biophysical and pharmacological properties of this current using voltage-clamp techniques. We will then use this information to assess its functional significance by recording membrane potential with intracellular microelectrodes simultaneously with contractile activity. We will also compare small vessels obtained from volunteers with or without the vasospastic disorder of Raynaud's phenomenon. Our previous work using these techniques was described in J Physiol as a microelectrode, patch clamp and myograph study of the highest quality and of supreme technical difficulty and scored a Top-Ten hit rate. Since we are the only ones to record the plateau current, we are in a unique position to make significant progress to our understanding of contraction, including spasm, in small blood vessels.Read moreRead less
Epilepsy is the name of a group of disorders where seizures occur. 5% of people will have at least one seizure. Seizures accompanied by fever (febrile) are common in early childhood. Most forms of epilepsy and febrile seizures have an inherited component. Progress in finding genes for common forms of epilepsy has been slow, probably because they are due to the interaction of a number of genes. Four genes for rare epilepsies with single gene inheritance have been identified. These genes code for ....Epilepsy is the name of a group of disorders where seizures occur. 5% of people will have at least one seizure. Seizures accompanied by fever (febrile) are common in early childhood. Most forms of epilepsy and febrile seizures have an inherited component. Progress in finding genes for common forms of epilepsy has been slow, probably because they are due to the interaction of a number of genes. Four genes for rare epilepsies with single gene inheritance have been identified. These genes code for subunits of ion channels in cells. We study families where many individuals have seizures and carefully diagnose the seizures types. This work has resulted in the description of 5 new inherited epilepsies and led to discovery of 3 of the 4 known genes. The most important new inherited epilepsy is Generalized Epilepsy with Febrile Seizures Plus (GEFS+). GEFS+ accounts for many children with febrile seizures restricted to early childhood, or where seizures continue into mid-childhood. GEFS+ families may contain an individual with severe generalized epilepsy with intellectual disability. In a Tasmanian family with GEFS+, we found a gene defect in the sodium channel of nerve cells in the brain. We plan to study more families with GEFS+. We believe that specific severe childhood epilepsies may occur in families with GEFS+. If so, then the underlying cause of these serious disorders may be gene defects of GEFS+. Finding such genes will help to understand the basis of seizures and ultimately lead to targeted therapies. The second major focus of our work on GEFS+ is to use family studies to understand how different types of seizures are inherited, and to gain insights into the gene interactions underlying common epilepsies. We plan to study isolated cases of GEFS+ for the gene defects found in families. This strategy will reveal whether the same genes are important in the genetics of the common epilepsies.Read moreRead less