Development of an adenoviral vector for intracerebral delivery of the dopamine D(2) receptor.
The age-related loss of striatal dopamine D(2) receptors (D(2)R) has been observed in numerous species, including rodents, monkeys, and man, and is partly responsible for impaired motor function in aged mammals. We have developed an adenoviral vector designed for intracerebral transfer of cDNA for D(2)R. Results of in vitro studies demonstrated that the vector produced abundant message for D(2)R and that the vector was membrane bound and capable of binding appropriate ligand. Results of in vivo studies provided clear evidence of D(2)R production when injected into the striatum of rats. The D(2)R produced were capable of binding appropriate ligand. In addition, evidence of functional receptors was produced by demonstrating apomorphine-induced rotational behavior in rats receiving a unilateral injection of the vector. Despite these successes, we have been unable to demonstrate improvement in the motor behavior of aged rats receiving bilateral injections of the vector. A major problem with this vector as with similar adenoviral vectors is the loss of expression beginning 3-5 days after injection to undetectable levels at 21 days. Because of the lack of motor functional effects in aged rats and the loss of expression of the vector, other strategies for development of the vector are being pursued. Regarding functional effects, we have examined the feasibility of manipulating hippocampal acetylcholine (ACh) release through D(2)R manipulation to improve memory performance. Using microdialysis, we have demonstrated in vivo in rats that treatment with a D(2)R agonist increases hippocampal ACh release while treatment with a D(2)R antagonist attentuates this effect as well as impairs performance in a complex maze task. In addition, a D(2)R null mutant mouse is being used to examine possible therapeutic effects of the vector. These mice show specific motor deficits. Recent studies using positron emission tomography have also demonstrated the feasibility of in vivo imaging of the vector. Thus, use of adenoviral vectors specific for neurotransmitter receptors can provide a highly useful research tool for examining age-related alterations in behavioral function and a possible strategy for therapeutic intervention.
Ingram
D K
DK
Molecular Physiology and Genetics Section, Laboratory of Cellular and Molecular Biology, Gerontology Research Center, National Institute on Aging, 5600 Nathan Shock Lane, Baltimore, MD 21224, USA.
Roth
G S
GS
Umegaki
H
H
Ikari
H
H
D000109:Acetylcholine / Q000378:metabolism; D000260:Adenoviruses, Human; D000818:Animals; D015870:Gene Expression; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007267:Injections; D007858:Learning / Q000502:physiology; D051379:Mice; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D017448:Receptors, Dopamine D2 / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D013687:Telencephalon
D017448:Receptors, Dopamine D2; D000109:Acetylcholine