Stephan G. Anagnostaras - US grants

The proximal objective of the project is to examine what role, if any, protein synthesis and CREB-mediated transcription play in the long-term stabilization of spatial representations in the hippocampus. These place representations are believed to be used by animals to solve spatial learning problems. Likewise, the long-term (but not short-term) stability of memory depends on protein synthesis and CREB-mediated transcription. First, the effect of cerebral protein synthesis inhibition on the stability of hippocampal place representations will be examined in mice according to a conventional technique. Second, two novel techniques for inducing CREB disruption have been developed and are both expected to produce deficits in long-term, but not short-term stability of the hippocampal spatial map. The specific aims of the proposal are to examine the effects on hippocampal place cell firing field stability of [1] protein synthesis inhibiton in wildtype mice, [2] inhibition of the cAMP/PKA pathway, via dopamine D1/D5 receptor blockade, in heterozygous CREBalphadelta+/- mice, and [3] the induction of a CREB repressor in transgenic mice. The ultimate objective is to test the hypothesis that spatial representations maintained by place cells mediate long-term spatial memory. This research will improve our understanding of the cellular mechanisms of hippocampus-dependent memory.

DESCRIPTION (provided by applicant): Behavioral sensitization results from repeated intermittent use of stimulant drugs, and may contribute to addiction. Prior studies investigating the influence of associative pairing of contextual stimuli with psychostimulant administration on the expression of psychomotor sensitization in rodents have shown that under certain circumstances, sensitization can be context-specific. Based on these and other findings, we proposed that three memory mechanisms regulate the context-specificity of stimulant sensitization: (1) Repeated drug administration induces sensitization of the neural substrate that mediates the unconditional response (UR) to the drug, a form of non-associative learning. (2) An inhibitory process can block the expression of neural sensitization in contexts where the drug is not expected, a process involving inhibitory occasion-setting. (3) An excitatory conditioned response (CR) can amplify the sensitized response in a context where the drug is expected, and produces a CR, which may contribute to craving, in the absence of the drug. The ability of drug-associated contexts to modulate the expression of neural sensitization via occasion-setting may combine with the ability of a drug-associated context to produce conditioned responses, together providing powerful associative control over not only behavioral sensitization, but in addicts, over craving and relapse. In the current proposal, we will investigate if distinct neural memory systems selectively mediate memory processes involved in behavioral sensitization. First, we will use mice to optimize the behavioral paradigm for studying memory processes underlying stimulant sensitization, developing a procedure which produces robust sensitization, rapid acquisition (so that distinct memory phases may be examined), and measuring sensitization, context-specificity, and conditioned responses. Following establishment of this paradigm, we will attempt to identify critical neural substrates of these processes by examining the impact of lesions of memory-related brain structures, including the hippocampus and amygdala. Finally, using this novel mouse paradigm, we will investigate the molecular neurobiology of these processes, examining mice with targeted genetic mutations known to disrupt memory. This approach, using systems and molecular methods, should elucidate whether structures and genes known to be important for learning and memory are similarly crucial for the expression of stimulant sensitization.

Disruption of cholinergic muscarinic receptors produces an array of profound deficits in attention, memory acquisition, and memory consolidation. Likewise, cognitive decline in Alzheimer's disease and in normal aging is associated with cholinergic dysfunction. The M1receptor has become a focus of pharmacological treatment for memory deficits, perhaps because it is the most widely distributed muscarinic receptor in the hippocampus and cortex. Here we examine the relevance of selective cognitive deficits we have found in M1 knockout mice to cognitive decline in aging. In specific aim 1, we extend the cognitive phenotype of the M1 knockout. We then compare this phenotype to normal aged mice in aim 2, in order to determine if the young M1knockout and aged mouse share any deficits in cognition. Finally in aim 3, we establish a colony of aging mutant and wildtype M1 mice. It is predicted that M1 mutants will show premature further decline in aging. Specifically the M1 heterozygous deletion, which does not produce cognitive deficits, may begin to exhibit them with aging. These studies will form the basis for an investigation of the relevance of the M1 receptor to cognitive decline in aging.

[unreadable] DESCRIPTION (provided by applicant): Both memory and addiction produce long-lasting changes in behavior and result in chronic neural adaptations in response to repeated neural activity. It is therefore likely that memory and addiction recruit some of the same molecular mechanisms of synaptic plasticity in the same neural structures. In the present proposal, we explore the parallels between addiction and memory by examining the impact of genetic and anatomical manipulations known to affect memory on addiction-related behavioral plasticity. In a simple behavioral paradigm in mice we can rapidly quantify psychomotor sensitization to repeated cocaine injections, as well as the conditioned response to cues associated with cocaine administration, the contextual control over the expression of cocaine sensitization, and conditioned place preference induced by cocaine. First, we use this paradigm to evaluate the role of the hippocampus and amygdala in addiction-related memory. Second, we use inducible and region-specific disruption of calcium/calmodulin- dependent protein kinase II (CaMKII), a criticial kinase in memory formation, in addiction. Finally, we examine the role of calcium calmodulin in addiction. A benefit of using modern genetic manipulation is the ability to better localize key neuroadaptations through disruption of dendritic translation, and inducible region-specific disruption of alpha-CaMKI in the forebrain and striatum. The inducible and reversible molecular manipulations we propose, post-induction disruption of CaMKII or calcium calmodulin, actually have the potential to reverse sensitization to cocaine and related memories. Taken together, these studies will evaluate the parallels between memory and addiction-related behavioral plasticity and shed considerable light on whether manipulations of memory will prove useful in the treatment of addiction.Project Narrative Addiction is a major social and medical problem affecting millions of compulsive drug users. In the present proposal we examine the relationship between memory and addiction at the level of the brain. If memory and addiction prove to be highly related, disruptions of memory may prove highly useful in the treatment of addiction. [unreadable] [unreadable] [unreadable]