The erythropoietin-derived peptide ARA290 reverses mechanical allodynia in the neuritis model.

Studies on the neuritis model suggest that in many patients with neuropathic pain, symptoms may be due to nerve inflammation rather than frank nerve injury. Treatments for these patients are often ineffective. The neuroprotective and hematopoietic agent erythropoietin (EPO) has been shown to reverse pain behaviors in nerve injury models and therefore may be of therapeutic benefit. However, EPO can cause thrombosis. ARA290 is an analog of EPO that has the neuroprotective activities of EPO without stimulating hematopoiesis. The present study has examined the effects of ARA290 on pain behavior in the neuritis model. Following neuritis induction, 30 or 120 µg/kg ARA290 or saline vehicle was injected intraperitoneally into rats daily from day 1 post surgery. Animals were assessed for mechanical allodynia and heat hyperalgesia. Levels of the cytokine tumor necrosis factor-α (TNF-α) and chemokine (CC motif) ligand 2 (CCL2) mRNA were also assessed using polymerase chain reaction. Vehicle-treated neuritis animals (n=20) developed signs of mechanical allodynia and heat hyperalgesia that reached a maximum on day 4 and 3 of testing, respectively. Treatment with either 30 (n=11) or 120 µg/kg ARA290 (n=9) prevented the development of mechanical allodynia. However, ARA290 did not significantly affect heat hyperalgesia. There was no significant difference between the effects of each drug dose (p<0.05, unpaired t test comparing area under the curve for mechanical allodynia). The levels of CCL2 and TNF-α mRNA in the nerve and Gelfoam were not significantly different following 120 µg/kg ARA290 treatment (n=3-7) compared to vehicle-treated animals (n=3-7; p=0.24; unpaired t tests). In summary, ARA290 may be beneficial in the treatment of neuropathic pain symptoms where signs of nerve injury are absent on clinical assessment. The mechanisms of action do not appear to involve the inhibition of TNF-α or CCL2 production.

Intra-accumbens baclofen, but not muscimol, mimics the effects of food withdrawal on feeding behaviour.

Intra-accumbens stimulation of GABA receptors results in a robust increase in food intake. However the differential consequences of stimulating GABA(A) and GABA(B) receptors in the nucleus accumbens have not been extensively explored with respect to feeding behaviour. Here we compare the effects of the GABA(B) receptor agonist baclofen and GABA(A) receptor agonist muscimol, infused into the nucleus accumbens shell, on food intake and related behavior patterns. Baclofen (110-440 ρmol) dose dependently enhanced intake and delayed the onset of satiety within the test period as did the effects of 4-8h food withdrawal. Muscimol (220-660 ρmol) enhanced intake but also disrupted the sequence of associated behaviours at every dose tested. We conclude that GABA(B) receptors in the nucleus accumbens shell may play a role in relation to feeding motivation whereas GABA(A) receptors may, as previously suggested, have a more restricted role in relation to the motor components of approach to food and ingestion.

Serotonergic characteristics of rainbow trout divergent in stress responsiveness.

Juvenile rainbow trout divergent in their cortisol response to confinement stress (HR: high responsive or LR: low responsive fish) were exposed to either 1 or 3 h of confinement stress. Untreated fish served as control. After the exposure blood and brain samples were collected. From the blood samples, the levels of cortisol and catecholamines were determined, while the brain serotonergic and monoamineoxidase (MAO) activity was determined in four different brain areas (brain stem, hypothalamus, telencephalon and optic tectum). Our results show that the LR fish responds to handling stress with a higher increase in plasma epinephrine compared to HR fish. Our results also show that confinement stress leads to a larger increase in the serotonergic activity in the brain stem and telencephalon in LR fish compared to HR fish. These results support the hypothesis that stress coping strategies similar to those described in mammals also exists in fish. Further, our results have shown that the MAO activity increases in optic tectum and hypothalamus of rainbow trout during confinement stress, while it remains unchanged or decreases in brain stem and telencephalon. Moreover, the MAO activity does not differ between the two selection lines. This indicates that MAO participates actively in the stress response without contributing to the differences in stress coping strategies.

Contamination of headwater streams in the United Kingdom by oestrogenic hormones from livestock farms.

Most studies of hormonal activity in rivers have focused on inputs from sewage treatment works (STW), and their consequences for endocrine disruption in fish. It is possible that livestock is contributing to this hormonal activity in rivers. This study represents a search for evidence of steroid hormone contamination in streams associated with livestock farms. The majority of the 10 sites selected were streams running through dairy farms, although some examples of beef, sheep and pigs were included. Passive water samplers (Polar Organic Chemical Integrative Samplers-POCIS) were deployed up- (control) and down-stream of the farms for 3 to 10 weeks (mean=39 days) during the period November 2004 to January 2005. At one site, water samples were also taken automatically during rainfall events. All samples were solvent-extracted. Total oestrogenic activity in concentrates of the extracts was analysed using the Yeast Estrogen Screen (YES) calibrated against 17beta-oestradiol (E2), while oestrone (E1), E2 and 17alpha-ethinylestradiol (EE2) were analysed by liquid chromatography-mass spectrometry (LC-MS/MS). Stream water from the entirety of only one rainfall event was sampled directly, but this revealed background activity (E2 equivalents) of 0-0.3 ng/l, rising to a transient peak of 9.4 ng/l. Average oestrogenic activity at this site as estimated from the POCIS samplers was 1.8-2.7 ng E2 equiv./l. Estimated average oestrogenic activity across all sites (with one exception) lay in the range 0-26.5 ng E2 equiv./l (mean=2.0 ng/l; S.D.=5.1), based on the POCIS samples. The outlier was 292 ng/l, and this could not be specifically linked with livestock rearing. 92% of monitoring stations (at least one on each farm) contained some oestrogenic activity, and activity was higher at downstream sites in 50% of cases. Although no EE2 was detected analytically in any stream, E1 and E2 were almost ubiquitous, with E2 equivalents ranging from 0.04 to 3.6 ng/l across all sites. Furthermore, steroid concentrations downstream of livestock were higher than upstream in 60% of cases, more markedly so than for the YES data. In several cases, activity upstream was greater than downstream, and this tended to be associated with higher activity than could be accounted for by the hormone analyses. Both the YES and chemical analytical data suggest that fish in headwater streams on or near some livestock farms may be at risk of endocrine disruption.

Extinction of a conditioned response in rainbow trout selected for high or low responsiveness to stress.

Two lines of rainbow trout (Oncorhynchus mykiss) that exhibit divergent endocrine responsiveness to stressors also display disparate behavioral traits. To investigate whether the high-responding (HR) and low-responding (LR) fish also differ in cognitive function, the rate of extinction of a conditioned response was compared between the two lines. Groups of HR and LR fish were exposed to a paired conditioned stimulus (CS; water off) and unconditioned stimulus (US; confinement stressor). After exposure to 18 CS-US pairings, at least 70% of individuals of both lines acquired a conditioned response (CR) manifested as an elevation of blood cortisol levels on presentation of the CS only. Post-conditioning, the fish were tested by presentation of the CS at weekly intervals, for 4 weeks, with no further reinforcement, and the extinction of the CR in the two lines was compared. The decline in mean plasma cortisol levels after exposure to the CS over successive tests suggested that the CR was retained for a shorter period among the HR (<14 days) than LR fish (<21 days). The frequency of individuals within each line whose plasma cortisol levels indicated a stress response when exposed to the CS was significantly greater among the LR than HR fish at 14 and 21 days with no HR fish falling into this category at 21 days. At 28 days post-conditioning, there were no HR fish and only three LR fish were categorized as "stressed". These results suggest that there are differences in cognitive function between the two lines. Possible mechanisms underlying these differences are discussed.