ABSTRACT
Background: Drug seeking behavior occurs in response to environmental contexts and drug-associated cues. The presence of these pervasive stimuli impedes abstinence success. ß-adrenergic receptors (ß-ARs) have a long-standing historical implication in driving processes associated with contextual memories, including drug-associated memories in substance use disorders. However, sex differences in the role of ß-adrenergic receptors in drug memories remain unknown. Hypothesis: Prior reports indicate a selective role for ß2-ARs in retrieval and retention of contextual drug memories in males, and substantial sex differences exist in the expression of ß-ARs of male and female rats. Therefore, we hypothesized that there are sex differences in selective recruitment of ß-ARs during different stages of memory encoding and retrieval. Methods: The role of ß-ARs in driving retrieval and learning of contextual cocaine memories was investigated using cocaine conditioned place preference (CPP) in adult male and female Sprague-Dawley rats. Rats were infused directly to the dorsal hippocampus with Propranolol (ß1 and ß2) or ICI-118,551 (ß1) and/or Betaxolol (ß2), immediately prior to testing (retrieval), or paired to each cocaine (10 mg/kp, IP) conditioning session (learning). Results: In males, administration of either ß1, ß2, or combined ß1 and ß2-ARs before the initial CPP testing reduced the expression of a CPP compared to vehicle administration. In females, ß2-ARs transiently decreased CPP memories, whereas ß1 had long lasting but not immediate effects to decrease CPP memories. Additionally, ß1 and combined ß1 and ß2-ARs had immediate and persistent effects to decrease CPP memory expression. DG Fos + neurons predicted cocaine CPP expression in males, whereas CA1 and CA3 Fos + neurons predicted cocaine CPP expression in females. Conclusion: There are significant sex differences in the role of dorsal hippocampus ß-ARs in the encoding and expression of cocaine conditioned place preference. Furthermore, sub regions of the dorsal hippocampus appear to activate differently between male and female rats during CPP. Therefore DG, CA3, and CA1 may have separate region- and sex-specific impacts on driving drug- associated, or context-associated cues.
ABSTRACT
Ipomoea purpurea (common morning glory) is an annual vine native to Mexico that is well known for its large, showy flowers. Humans have spread morning glories worldwide, owing to the horticultural appeal of morning glory flowers. Ipomoea purpurea is an opportunistic colonizer of disturbed habitats including roadside and agricultural settings, and it is now regarded as a noxious weed in the Southeastern US. Naturalized populations in the Southeastern United States are highly polymorphic for a number of flower color morphs, unlike native Mexican populations that are typically monomorphic for the purple color morph. Although I. purpurea was introduced into the United States from Mexico, little is known about the specific geographic origins of US populations relative to the Mexican source. We use resequencing data from 11 loci and 30 I. purpurea accessions collected from the native range of the species in Central and Southern Mexico and 8 accessions from the Southeastern United States to infer likely geographic origins in Mexico. Based on genetic assignment analysis, haplotype composition, and the degree of shared polymorphism, I. purpurea samples from the Southeastern United States are genetically most similar to samples from the Valley of Mexico and Veracruz State. This supports earlier speculation that I. purpurea in the Southeastern United States was likely to have been introduced by European colonists from sources in Central Mexico.
