The focus of this research program is the influence of paternal cocaine taking on the physiology and behavior of subsequent generations (i.e. offspring and grandoffspring). Human epidemiological data indicates that cocaine addiction is often accompanied by cognitive decline including episodic memory impairments. Our working hypothesis is that paternal cocaine exposure elicits learning and synaptic plasticity impairments in male offspring and grandoffspring by reducing D-serine levels/NMDA receptor signaling in the hippocampus.
In Specific Aim 1, learning and memory as well as long term potentiation (LTP), a generally accepted physiological learning correlate, will be assessed in the offspring of sires that self-administered cocaine. Preliminary findings from object-based memory assays indicate that male, but not female, offspring and grandoffspring of cocaine-exposed sires have impaired hippocampus-dependent object location memory. Paternal cocaine exposure also impairs hippocampal LTP in male offspring.
In Specific Aim 2 we will evaluate the hypothesis that these learning and synaptic plasticity deficits in the adult descendants of cocaine- experienced sires are due to decreased dorsal hippocampal D-serine/NMDA receptor signaling, which are critically involved in spatial learning and synaptic plasticity. Preliminary data indicate that D-serine levels are decreased in the dorsal hippocampus of cocaine-sired male rats. The enzyme D-amino acid oxidase (DAAO) catalyzes the oxidative deamination of D-serine. Preliminary data indicate that daao1 mRNA levels are increased in the dorsal hippocampus of cocaine-sired male rats. To examine potential epigenetic mechanisms underlying the increase in daao1 mRNA, histone posttranslational modifications associated with daao1 will be examined in F1 and F2 generations. Finally, D-serine, D-cycloserine or a DAAO inhibitor will be administered into the dorsal hippocampus or onto hippocampal slices of cocaine-sired or cocaine-grandsired rats, which we predict will rescue spatial learning and plasticity deficits.
In Specific Aim 3 we will evaluate how information is transferred between generations by assessing miRNA changes in the sperm of cocaine-experienced sires and their offspring. Preliminary data indicate that cocaine self-administration significantly altered four miRNAs (miR- 1-3p, miR-206-3p, miR-1b, miR-362-3p) in sire sperm. In order to determine if the CNS is required for the effect of cocaine on sperm miRNAs we will compare self-administered cocaine to yoked cocaine methiodide, which does not cross the blood-brain barrier. We also will assess the duration of cocaine-induced changes in sperm by evaluating miRNAs 1 or 90 days following cocaine self-administration. Collectively, these experiments will determine changes in hippocampal function in the descendants of cocaine-experienced sires that contribute to learning deficits in these animals. We also will examine cocaine-induced changes in sperm that may carry information between generations. Overall, we define a novel model of heritable cocaine-induced learning deficits. These results have clear and significant implications for the descendants of cocaine addicts.
A growing body of evidence indicates that environmental information can be inherited, which suggests that changes in the mammalian germline can act as a trans-generational carrier of environmental information. Here, we describe a rat model developed in order to delineate heritable behavioral characteristics resulting from the self-administration of cocaine. Our results indicate that the male progeny and grand-progeny of cocaine experienced sires have learning deficits. The experiments described in this application will use state-of-the-art molecular, electrophysiological and behavioral methodologies to examine the mechanisms whereby cocaine- associated information can be transmitted from sires to offspring and assess specific neuronal changes that may underlie this paternally transmitted phenotype associated with cocaine self-administration.
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