Learning disabilities are the most common behavioral deficit observed in children with Fetal Alcohol Spectrum Disorder. The development of effective pharmacotherapeutic interventions for these disabilities requires a clearer understanding of the neurobiologic bases of fetal ethanol-induced learning deficits and subsequently, the identification of therapeutic agents whose mechanisms of action would be predicted to have clinical utility. We have observed that the histamine H3 receptor antagonist ABT-239 ameliorates fetal ethanol-induced deficits in dentate gyrus long-term potentiation (LTP) and learning. We have also observed increased H3 receptor-effector coupling in dentate gyrus of fetal ethanol offspring. Given that presynaptic H3 receptors inhibit glutamate release;our results suggest that fetal ethanol exposure increases H3 receptor-mediated inhibition of glutamate release, and that ABT-239 reduces this heightened inhibitory influence. We hypothesize that: Fetal ethanol exposure elevates presynaptic histamine H3 receptor function in dentate gyrus. This heightened inhibitory influence reduces glutamate release at the perforant path - dentate granule cell synapse which, in turn, contributes to deficits in LTP and learned behaviors sensitive to functional damage in the dentate gyrus. To test this hypothesis, our specific aims will examine: 1: The binding of [3H]-A349821, a selective H3 receptor antagonist, in dentate gyrus to quantitate H3 receptor density in control and fetal alcohol offspring (Aim 1A). We will also use the selective H3 receptor agonist methimepip to conduct methimepip-displacement of [3H]-A349821 binding studies to determine the proportion of high- and low-affinity agonist binding sites of the H3 receptor (Aim 1B) and examine H3 receptor-effector coupling by measuring methimepip-stimulated [35S]-GTPgS binding (Aim 1C). 2: The effects of methimepip and ABT-239 on glutamate and GABA release by measuring paired-pulse plasticity and miniature postsynaptic currents along with the effects of these agents on LTP at perforant path dentate granule cell synapses in control and fetal ethanol-exposed offspring. 3: The effects of methimepip and ABT-239 on paired-pulse plasticity and LTP at the perforant path - granule cell synapse in vivo in control and fetal ethanol-exposed offspring. 4: The effects of methimepip on one-trial contextual fear conditioning (Aim 4A) and spatial navigation (Aim 4B) and the effects of methimepip and ABT-239 on a spatial pattern-separation variant of the radial arm maze (Aim 4C) in control and fetal ethanol-exposed offspring. We anticipate that these studies will provide important new insights on the impact of fetal ethanol exposure on histaminergic modulation of glutamatergic neurotransmission and synaptic plasticity in the dentate gyrus. In addition, the results could provide a preclinical pharmacologic rationale for considering drugs that act as H3 receptor antagonists as putative therapeutic agents for the treatment of learning deficits in humans with FASD.

Public Health Relevance

Despite public awareness campaigns warning of the dangers of drinking during pregnancy, it is estimated that between 2% and 5% of children born in the United States each year have fetal alcohol-associated functional brain damage that will lead to learning deficits over time. Currently, there are no evidence-based clinically useful pharmacotherapeutic interventions for these deficits. The long-term objective of our research program is understand the neurobiologic bases of fetal ethanol-induced learning deficits and subsequently, to identify therapeutic agents whose mechanisms of action would be predicted to have clinical utility in treating fetal alcohol-associated learning disabilities.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
1R01AA019884-01A1
Application #
8205378
Study Section
Neurotoxicology and Alcohol Study Section (NAL)
Program Officer
Liu, Qi-Ying
Project Start
2011-08-01
Project End
2016-07-31
Budget Start
2011-08-01
Budget End
2012-07-31
Support Year
1
Fiscal Year
2011
Total Cost
$313,142
Indirect Cost
Name
University of New Mexico Health Sciences Center
Department
Neurosciences
Type
Schools of Medicine
DUNS #
829868723
City
Albuquerque
State
NM
Country
United States
Zip Code
87131
Varaschin, Rafael K; Allen, Nyika A; Rosenberg, Martina J et al. (2018) Prenatal Alcohol Exposure Increases Histamine H3 Receptor-Mediated Inhibition of Glutamatergic Neurotransmission in Rat Dentate Gyrus. Alcohol Clin Exp Res 42:295-305
Bird, Clark W; Barto, Daniel; Magcalas, Christy M et al. (2017) Ifenprodil infusion in agranular insular cortex alters social behavior and vocalizations in rats exposed to moderate levels of ethanol during prenatal development. Behav Brain Res 320:1-11
Noor, Shahani; Sanchez, Joshua J; Vanderwall, Arden G et al. (2017) Prenatal alcohol exposure potentiates chronic neuropathic pain, spinal glial and immune cell activation and alters sciatic nerve and DRG cytokine levels. Brain Behav Immun 61:80-95
Rodriguez, Carlos I; Magcalas, Christy M; Barto, Daniel et al. (2016) Effects of sex and housing on social, spatial, and motor behavior in adult rats exposed to moderate levels of alcohol during prenatal development. Behav Brain Res 313:233-243
Rodriguez, Carlos I; Davies, Suzy; Calhoun, Vince et al. (2016) Moderate Prenatal Alcohol Exposure Alters Functional Connectivity in the Adult Rat Brain. Alcohol Clin Exp Res 40:2134-2146
Bird, Clark W; Candelaria-Cook, Felicha T; Magcalas, Christy M et al. (2015) Moderate prenatal alcohol exposure enhances GluN2B containing NMDA receptor binding and ifenprodil sensitivity in rat agranular insular cortex. PLoS One 10:e0118721
Hamilton, Derek A; Magcalas, Christy M; Barto, Daniel et al. (2014) Moderate prenatal alcohol exposure and quantification of social behavior in adult rats. J Vis Exp :
Staples, Miranda C; Porch, Morgan W; Savage, Daniel D (2014) Impact of combined prenatal ethanol and prenatal stress exposures on markers of activity-dependent synaptic plasticity in rat dentate gyrus. Alcohol 48:523-32
Hamilton, Derek A; Barto, Daniel; Rodriguez, Carlos I et al. (2014) Effects of moderate prenatal ethanol exposure and age on social behavior, spatial response perseveration errors and motor behavior. Behav Brain Res 269:44-54
Varaschin, Rafael K; Rosenberg, Martina J; Hamilton, Derek A et al. (2014) Differential effects of the histamine H(3) receptor agonist methimepip on dentate granule cell excitability, paired-pulse plasticity and long-term potentiation in prenatal alcohol-exposed rats. Alcohol Clin Exp Res 38:1902-11

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