Modulation of Ion Channels by Cannabinoid Receptors in Rat Sympathetic Neurons

Hdl Handle:
http://hdl.handle.net/10675.2/553074
Title:
Modulation of Ion Channels by Cannabinoid Receptors in Rat Sympathetic Neurons
Authors:
Pan, Xianghua
Abstract:
The rat brain cannabinoid receptor (CB1) is a member of the G protein coupled receptor family. The present study directly tested the functional coupling of CB1 receptor with neuronal ion channels. The rat CB1 receptor was heterologously expressed by microinjection o f cRNA into the enzymatically dissociated adult rat superior cervical ganglion (SCG) neurons. The cannabinoid receptor agonists WIN 55,212-2 and CP 55940 produced a voltagedependent inhibition of whole cell Ca2+ currents. The maximal inhibitions o f the Ca2+ current by WIN 55,212-2 and CP 55,940 were 73% and 38%, respectively. The E C 50 of WIN 55,212-2 was 47 nM and the EC50 of CP 55940 was 7 nM. The inhibition was mediated by pertussis toxin (PTX) sensitive G protein and the N-type Ca2+ channels are the targets. The L-type Ca2+ channels, M type K+ current and the A current were not modulated by WIN 55,212-2. An inwardly rectifying current was activated by WIN 55,212-2. The selective CB1 receptor antagonist SR 141716A and LY 320135 abolished the inhibition of the Ca2+ currents by WIN 55,212-2. However, when given alone, SR 141716A and LY 320135 increased the Ca2+ current in SCG neurons expressing the CB1 receptor. SR 141716A increased Ca2+ current with an EC50 of 32 nM and a maximal current increase of 41% at 1 p.M. This increase of Ca2+ current by SR 141716A was a reversal o f a tonic inhibition of Ca2+ current in neurons expressing CB 1 receptors. A K192A mutant of the human CB1 receptor was tested to determine whether the tonic activation o f the cannabinoid receptor is due to endogenous arachidonyl ethanolam ide (anandam ide). The K192A m utant receptor was expressed by microinjection of receptor cDNA into nucleus of the SCG neurons. WIN 55,212-2 inhibited the Ca2+ current in these SCG neurons, but SR 141716A did not increase the Ca2+ current. However, SR 141716A inhibited the effect of WIN 55,212-2. Ca2+ currents from male rat major pelvic ganglion neurons were examined for modulation by native cannabinoid receptors. WIN 55,212-2 inhibited and SR 141716A increased the \ '>ltage-dependent Ca2+ currents in a subpopulation of the rat major pelvic ganglion neurons. 1 (J.M WIN 55,212-2 inhibited current by 26.1±1.8% and 1 pM SR 141716A increased current by 27.4±6.9%. These findings indicate that both heterologously expressed CB1 cannabinoid receptors and the native neuronal cannabinoid receptors can inhibit voltage-dependent Ca2+ channels. There is a tonic activation of both the heterologously expressed rat and human CB1 receptor and the native rat cannabinoid receptor. Two possible mechanisms may be responsible for the tonic receptor activation: an endogenous agonist may exist or the cannabinoid receptor can adopt an active conformational state such that SR 141716A may act as an inverse agonist.
Affiliation:
Department of Pharmacology and Toxicology
Issue Date:
Sep-1996
URI:
http://hdl.handle.net/10675.2/553074
Additional Links:
http://ezproxy.augusta.edu/login?url=http://search.proquest.com/docview/304329725?accountid=12365
Type:
Dissertation
Appears in Collections:
Theses and Dissertations; Department of Pharmacology and Toxicology Theses and Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.authorPan, Xianghuaen
dc.date.accessioned2015-05-18T19:53:48Zen
dc.date.available2015-05-18T19:53:48Zen
dc.date.issued1996-09en
dc.identifier.urihttp://hdl.handle.net/10675.2/553074-
dc.description.abstractThe rat brain cannabinoid receptor (CB1) is a member of the G protein coupled receptor family. The present study directly tested the functional coupling of CB1 receptor with neuronal ion channels. The rat CB1 receptor was heterologously expressed by microinjection o f cRNA into the enzymatically dissociated adult rat superior cervical ganglion (SCG) neurons. The cannabinoid receptor agonists WIN 55,212-2 and CP 55940 produced a voltagedependent inhibition of whole cell Ca2+ currents. The maximal inhibitions o f the Ca2+ current by WIN 55,212-2 and CP 55,940 were 73% and 38%, respectively. The E C 50 of WIN 55,212-2 was 47 nM and the EC50 of CP 55940 was 7 nM. The inhibition was mediated by pertussis toxin (PTX) sensitive G protein and the N-type Ca2+ channels are the targets. The L-type Ca2+ channels, M type K+ current and the A current were not modulated by WIN 55,212-2. An inwardly rectifying current was activated by WIN 55,212-2. The selective CB1 receptor antagonist SR 141716A and LY 320135 abolished the inhibition of the Ca2+ currents by WIN 55,212-2. However, when given alone, SR 141716A and LY 320135 increased the Ca2+ current in SCG neurons expressing the CB1 receptor. SR 141716A increased Ca2+ current with an EC50 of 32 nM and a maximal current increase of 41% at 1 p.M. This increase of Ca2+ current by SR 141716A was a reversal o f a tonic inhibition of Ca2+ current in neurons expressing CB 1 receptors. A K192A mutant of the human CB1 receptor was tested to determine whether the tonic activation o f the cannabinoid receptor is due to endogenous arachidonyl ethanolam ide (anandam ide). The K192A m utant receptor was expressed by microinjection of receptor cDNA into nucleus of the SCG neurons. WIN 55,212-2 inhibited the Ca2+ current in these SCG neurons, but SR 141716A did not increase the Ca2+ current. However, SR 141716A inhibited the effect of WIN 55,212-2. Ca2+ currents from male rat major pelvic ganglion neurons were examined for modulation by native cannabinoid receptors. WIN 55,212-2 inhibited and SR 141716A increased the \ '>ltage-dependent Ca2+ currents in a subpopulation of the rat major pelvic ganglion neurons. 1 (J.M WIN 55,212-2 inhibited current by 26.1±1.8% and 1 pM SR 141716A increased current by 27.4±6.9%. These findings indicate that both heterologously expressed CB1 cannabinoid receptors and the native neuronal cannabinoid receptors can inhibit voltage-dependent Ca2+ channels. There is a tonic activation of both the heterologously expressed rat and human CB1 receptor and the native rat cannabinoid receptor. Two possible mechanisms may be responsible for the tonic receptor activation: an endogenous agonist may exist or the cannabinoid receptor can adopt an active conformational state such that SR 141716A may act as an inverse agonist.en
dc.relation.urlhttp://ezproxy.augusta.edu/login?url=http://search.proquest.com/docview/304329725?accountid=12365en
dc.rightsCopyright protected. Unauthorized reproduction or use beyond the exceptions granted by the Fair Use clause of U.S. Copyright law may violate federal law.en
dc.subjectCannabinoid Receptoren
dc.subjectCa2+ Channelsen
dc.subjectSympathetic Neuronen
dc.subjectHeterologous Expressionen
dc.subjectWIN 55,23 12-2en
dc.subjectAnandamideen
dc.subjectInverse Agonisten
dc.titleModulation of Ion Channels by Cannabinoid Receptors in Rat Sympathetic Neuronsen
dc.typeDissertationen
dc.contributor.departmentDepartment of Pharmacology and Toxicologyen
dc.description.advisorLewis, Deborah L.en
dc.description.committeeIkeda, Stephen R.; Caldwell, Robert W.; Carrier, Gerald O.; Creazzo, Tony L.; Wei, Xiangyangen
dc.description.degreeDoctor of Philosophy (Ph.D.)en
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