Dysfunction of the amygdala and hippocampus can cause anxiety disorders. Various neurotransmitters and drugs with anxiolytic effects modulate these brain areas by activating Gi/o protein coupled receptors (Gi/oPCRs). Gi/oPCRs inhibit presynaptic CaV2.2 channels, which control transmitter release at excitatory and inhibitory synapses in the hippocampus and amygdala. Therefore, the hypothesis of this project is that activation of Gi/oPCRs inhibits presynaptic CaV2.2 channels and reduces anxiety levels. My research plan combines molecular biology, behavior and synaptic electrophysiology of neuronal circuits related to anxiety.
The specific aims of this project are: a) To determine if reduction of Gi/oPCR coupling to CaV2.2 channels impacts neurotransmitter release in hippocampal synapses. The Lipscombe lab showed that elimination of exon 37a in the CaV2.2 gene decreases channel sensitivity to Gi/oPCR inhibition. To establish a synaptic role, we generated a mouse that lacks exon 37a. Our initial data showed a lower paired-pulse ratio in the medial perforant path- dentate gyrus of 37a-lacking mice compared to WT, suggesting an increase in neurotransmitter release produced by a reduction of Gi/oPCR inhibition of CaV2.2 channels. In this aim, I will further analyze the effect of the lack of coupling between Gi/oPCRs and CaV2.2 on the neurotransmitter release in hippocampus. b) To determine if the disruption of Gi/oPCR coupling to CaV2.2 channels affect anxiety-related behavior. In our initial studies, e37a-lacking mice exhibited shorter latency times to feed in novelty-induced hypophagia compared to wild-type, suggesting that reduction of Gi/oPCR inhibitory action on CaV2.2 channels lowers anxiety levels. I will extend and confirm these exciting results using open field and elevated zero maze. c) To determine if the inhibition of CaV2.2 channels by Gi/oPCR on gabaergic synapses of basolateral amygdala is upregulated during anxiety states. Previous reports have associated anxiety to a reduction in gabaergic transmission in basolateral amygdala. Most studies have documented changes postsynaptically during anxiety but surprisingly little is known about presynaptic control of transmitter release. In this aim, I will determine whether CaV2.2-dependent GABA release is reduced in the amygdala during anxiety states. d) To determine if the inhibition of CaV2.2 channels by Gi/oPCR agonists on glutamatergic synapses is down regulated during tolerance to anxiolytics. Using mouse models of tolerance, I will measure the sensitivity CaV2.2 channels to Gi/oPCR inhibition mediated by exogenous agonists in na?ve and drug-treated mice in glutamatergic transmission.

Public Health Relevance

Anxiety disorders are very prevalent conditions and effective treatments are scarce. Thus looking for alternatives to current pharmacological methods is a priority for researchers in the field. This project proposes to study the CaV2.2 channel as a novel target for drugs with marked anxiolytic effects.

National Institute of Health (NIH)
National Institute of Mental Health (NIMH)
Career Transition Award (K99)
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Special Emphasis Panel (ZMH1-ERB-L (06))
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Desmond, Nancy L
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Brown University
Schools of Medicine
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Groen, Justus L; Andrade, Arturo; Ritz, Katja et al. (2015) CACNA1B mutation is linked to unique myoclonus-dystonia syndrome. Hum Mol Genet 24:987-93
Lipscombe, Diane; Andrade, Arturo (2015) Calcium Channel CaV?? Splice Isoforms - Tissue Specificity and Drug Action. Curr Mol Pharmacol 8:22-31
Lipscombe, Diane; Andrade, Arturo; Allen, Summer E (2013) Alternative splicing: functional diversity among voltage-gated calcium channels and behavioral consequences. Biochim Biophys Acta 1828:1522-9
Felix, Ricardo; Calderón-Rivera, Aida; Andrade, Arturo (2013) Regulation of high-voltage-activated Ca(2+) channel function, trafficking, and membrane stability by auxiliary subunits. Wiley Interdiscip Rev Membr Transp Signal 2:207-220
Jiang, Yu-Qiu; Andrade, Arturo; Lipscombe, Diane (2013) Spinal morphine but not ziconotide or gabapentin analgesia is affected by alternative splicing of voltage-gated calcium channel CaV2.2 pre-mRNA. Mol Pain 9:67
Calderón-Rivera, Aida; Andrade, Arturo; Hernández-Hernández, Oscar et al. (2012) Identification of a disulfide bridge essential for structure and function of the voltage-gated Ca(2+) channel ?(2)?-1 auxiliary subunit. Cell Calcium 51:22-30
Marangoudakis, Spiro; Andrade, Arturo; Helton, Thomas D et al. (2012) Differential ubiquitination and proteasome regulation of Ca(V)2.2 N-type channel splice isoforms. J Neurosci 32:10365-9