Search

Author(s): Andrew D. Morgan (corresponding author) [1]; Sylvain Gandon [2]; Angus Buckling [1] Antagonistic coevolution between hosts and parasites in spatially structured populations can result in local adaptation of parasites [...]

Evidence is accumulating that the etiology, epidemiology, consequences and mechanisms that underlie drug abuse are different in males and females. In this review, we present examples of sex differences in all phases of drug abuse, including acquisition, steady-state maintenance, escalation, dysregulation, withdrawal, relapse and treatment. Most reported findings are based on laboratory research in animals, but there are corroborating reports from human clinical and epidemiological studies. In all phases of drug abuse, females seem to be more sensitive to the rewarding effects of drugs than males, and estrogen is a major factor that underlies these sex differences.

Abstract Background The dynamics of antagonistic host-parasite coevolution are believed to be crucially dependent on the rate of migration between populations. We addressed how the rate of simultaneous migration of host and parasite affected resistance and infectivity evolution of coevolving meta-populations of the bacterium Pseudomonas fluorescens and a viral parasite (bacteriophage). The increase in genetic variation resulting from small amounts of migration is expected to increase rates of adaptation of both host and parasite. However, previous studies suggest phages should benefit more from migration than bacteria; because in the absence of migration, phages are more genetically limited and have a lower evolutionary potential compared to the bacteria. Results The results supported the hypothesis: migration increased the resistance of bacteria to their local (sympatric) hosts. Moreover, migration benefited phages more than hosts with respect to 'global' (measured with respect to the whole range of migration regimes) patterns of resistance and infectivity, because of the differential evolutionary responses of bacteria and phage to different migration regimes. Specifically, we found bacterial global resistance peaked at intermediate rates of migration, whereas phage global infectivity plateaued when migration rates were greater than zero. Conclusion These results suggest that simultaneous migration of hosts and parasites can dramatically affect the interaction of host and parasite. More specifically, the organism with the lower evolutionary potential may gain the greater evolutionary advantage from migration.

The predatory capabilities of myxobacteria in nature are understood by analyzing the predation performance of numerous Myxococcus isolates across diverse species of bacteria. The broad prey range of the Myxococcus genus coupled with its ubiquity in the soil has shown that myxobacteria might have very important ecological and evolutionary effects on many species of soil prokaryotes.

Background: The dynamics of antagonistic host-parasite coevolution are believed to be crucially dependent on the rate of migration between populations. We addressed how the rate of simultaneous migration of host and parasite affected resistance and infectivity evolution of coevolving meta-populations of the bacterium Pseudomonas fluorescens and a viral parasite (bacteriophage). The increase in genetic variation resulting from small amounts of migration is expected to increase rates of adaptation of both host and parasite. However, previous studies suggest phages should benefit more from migration than bacteria; because in the absence of migration, phages are more genetically limited and have a lower evolutionary potential compared to the bacteria. Results: The results supported the hypothesis: migration increased the resistance of bacteria to their local (sympatric) hosts. Moreover, migration benefited phages more than hosts with respect to 'global' (measured with respect to the whole range of migration regimes) patterns of resistance and infectivity, because of the differential evolutionary responses of bacteria and phage to different migration regimes. Specifically, we found bacterial global resistance peaked at intermediate rates of migration, whereas phage global infectivity plateaued when migration rates were greater than zero. Conclusion: These results suggest that simultaneous migration of hosts and parasites can dramatically affect the interaction of host and parasite. More specifically, the organism with the lower evolutionary potential may gain the greater evolutionary advantage from migration. [ABSTRACT FROM AUTHOR]

Agmatine has been previously proposed to represent a novel neurotransmitter. One of the criteria required to test that hypothesis is that the exogenously administered chemical produces pharmacological effects similar to the physiological effects of the putative neurotransmitter. Since agmatine was first identified in brain, approximately sixty studies of the in vivo effects of exogenously administered agmatine have been reported. Despite the assertion that agmatine functions as a neuromodulator/neurotransmitter, the vast majority of experiments have administered agmatine through systemic (rather than central) routes of administration. Systemic delivery of agmatine for studies of centrally mediated phenomenona (e.g., pain, spinal cord injury, cardiovascular responses) relies on the presumption that agmatine (a polar compound) gains appreciable access to the CNS. The mechanism by which agmatine crosses the blood-brain barrier is not well understood. A number of studies have examined the in vivo effects of agmatine following central administration (e.g., intracerebroventricular and intrathecal). This paper summarizes and provides a comparison between the systemic versus central routes of administration for delivery of agmatine in experimental subjects. [ABSTRACT FROM AUTHOR]

Theory predicts that mixing in spatially structured populations of hosts and parasites can increase the rate of antagonistic coevolution. We experimentally tested this prediction by allowing populations of bacteria ( Pseudomonas fluorescens) and parasitic bacteriophage to coevolve in mixed and unmixed microcosms. Coevolution proceeded at approximately twice the rate in mixed populations compared with unmixed populations and caused the evolution of more resistant hosts and more infective parasites. [ABSTRACT FROM AUTHOR]

Multiple G protein-linked neurotransmitter systems have been implicated in the behavioral effects of cocaine. While actions of certain neurotransmitter receptor subtypes and transporters have been identified, the role of individual G protein-regulated enzymes and ion channels in the effects of cocaine remains unclear. Here, we assessed the contribution of G protein-gated, inwardly rectifying potassium (Kir3/GIRK) channels to the locomotor-stimulatory and reinforcing effects of cocaine using knockout mice lacking one or both of the key neuronal channel subunits, Kir3.2 and Kir3.3. Cocaine-stimulated increases in horizontal locomotor activity in wild-type, Kir3.2 knockout, Kir3.3 knockout, and Kir3.2/3.3 double knockout mice, with only minor differences observed between the mouse lines. In contrast, Kir3.2 and Kir3.3 knockout mice exhibited dramatically reduced intravenous self-administration of cocaine relative to wild-type mice over a range of cocaine doses. Paradoxically, Kir3.2/3.3 double knockout mice self-administered cocaine at levels significantly higher than either single knockout alone. These findings suggest that Kir3 channels play significant and complex roles in the reinforcing effect of cocaine. [ABSTRACT FROM AUTHOR]

Baclofen, a GABAB agonist, decreases both the maintenance and reinstatement of i.v. cocaine-reinforced responding in rats. In the present experiment the effects of baclofen were extended to a comparison of male and female rats during the acquisition of i.v. cocaine self-administration. Four groups of rats were trained to self-administer i.v. cocaine (0.2 mg/kg) under a fixed-ratio 1 (FR 1) schedule using an autoshaping procedure. The criterion for acquisition was a 5-day period during which a mean of 100 cocaine infusions were administered. Rats were given 30 days to reach this criterion. Male and female groups (n=10–13) were pretreated with i.p. injections of baclofen (2.5 mg/kg) or vehicle 30-min prior to the sessions. A subset of rats (N=5) that did not acquire cocaine self-administration continued to be exposed to the acquisition procedure after baclofen treatment ended. Pretreatment with baclofen decreased both the rate of acquisition of cocaine self-administration and the percentage of rats meeting the acquisition criterion to a greater extent in females than in males. Female rats that did not meet the acquisition criterion with baclofen treatment, acquired within a few days after treatment ended. The findings confirm previous reports of enhanced acquisition of cocaine self-administration in females versus males, and they indicate that baclofen suppressed the acquisition of cocaine self-administration significantly more in females than in males. [Copyright &y& Elsevier]

We still know very little about how the environment influences coevolutionary dynamics. Here, we investigated both theoretically and empirically how nutrient availability affects the relative extent of escalation of resistance and infectivity (arms race dynamic; ARD) and fluctuating selection (fluctuating selection dynamic; FSD) in experimentally coevolving populations of bacteria and viruses. By comparing interactions between clones of bacteria and viruses both within- and between-time points, we show that increasing nutrient availability resulted in coevolution shifting from FSD, with fluctuations in average infectivity and resistance ranges over time, to ARD. Our model shows that range fluctuations with lower nutrient availability can be explained both by elevated costs of resistance (a direct effect of nutrient availability), and reduced benefits of resistance when population sizes of hosts and parasites are lower (an indirect effect). Nutrient availability can therefore predictably and generally affect qualitative coevolutionary dynamics by both direct and indirect (mediated through ecological feedbacks) effects on costs of resistance., (© 2014 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.)