The role of the neuropeptide galanin in forming type-specific behavioral characteristics

Intranasal administration of a galanin receptor blocker to rats was found to change their behavioral type on being placed in an unfamiliar environment, with decreases in movement and investigative activity and increases in the level of anxiety in the open field test. The basal level of expression of the galanin precursor mRNA in the anterior hypothalamus was significantly higher in rats with the active type of behavior in the open field test. In conditions of galanin receptor blockade, there was also a faster increase in the serum corticosterone level in response to a stress situation (forced swimming test), which was accompanied by a reduction in the immobilization time. These data support the involvement of galanin in the formation of individual-typological behavioral characteristics and demonstrate its important role in adaptation to stress. __________ Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 92, No. 10, pp. 1204–1211, October, 2006.     

Evidence for galanin as an inhibitory neuropeptide on myenteric cholinergic neurons in the guinea pig small intestine

The effect of galanin on the [3H]ACh release from myenteric plexus-longitudinal muscle strips of the guinea pig small intestine was studied. While galanin did not alter the basal spontaneous efflux of ACh, it significantly depressed the ACh release evoked by electrical stimulation or caused by VIP and substance P. These results suggest an important neuromodulatory role for galanin in the enteric nervous system.     

Evidence for a role of the locus coeruleus noradrenaline system in learning

The effect of the new noradrenaline (NA) neurotoxin, DSP4, on the acquisition of one-way and two-way active avoidance responses was studied in rats. This treatment caused a marked degeneration of the iocus coeruleus NA system and markedly impaired both one- and two-way avoidance acquisition. Both effects were blocked by pretreatment with desipramine, a NA uptake blocking agent. The present findings support the hypothesis that the locus coeruleus NA system in its entire extent may play a role in aversive learning.     

Influence of the neuropeptide galanin on active avoidance in rats

It was demonstrated in experiments on rats that the injection of the neuropeptide, galanin (200, 500, and 1000 ng), into the lateral cerebral ventricles induced a dose-dependant decrease in the number of successful attempts at avoidance in rats trained preliminarily to active avoidance by jumping. The preliminary administration of the cholinolytic, atropine (1 mg/kg, intraperitoneally), to the rats also caused an acceleration of the damping of the conditioned reflex and potentiated the indicated effect of galanin during the experiment. The use of the opioid antagonist, naloxone (1 mg/kg, intraperitoneally), did not exert an influence on the animals' behavior, but blocked the galanin-provoked acceleration of the extinction of the active avoidance habit. The intraperitoneal administration of a noncompetitive antagonist of excitatory amino acids, ketamine (10 mg/kg), did not influence the character of the animals' behavior nor the indicated effects of galanin. It was concluded that galanin possesses an amnestic action in the active avoidance test, and that this effect of the peptide is determined by the suppression of cholinergic and activation of opiatergic transmission in the central nervous system.     

Evidence of a time-dependent long-term stage of memory for a spatial learning task in the chick (Callus gallus)

The generalizability of temporal parameters of memory formation previously observed for a passive avoidance task was investigated in a spatial task with day-old chicks (Callus gallus). The percentage improvement in completion time over 2 separate trials was measured, and chicks were found to complete the second trial faster at all times tested up to 2 hr, except at 55 min posttraining. In addition, retention at 120 min, but not at 30 min, posttraining was found to be impaired by protein synthesis inhibition. These findings are consistent with the timing of a long-term stage of memory formation following passive avoidance training, implying that there may be some hardwiring to the temporal characteristics of memory formation in this species.     

Comparison of the inhibitory roles of neuropeptide Y and galanin on cardiac vagal action in the dog.

Prolonged attenuation of cardiac vagal action occurs following cardiac sympathetic nerve stimulation or intravenous neuropeptide Y (NPY) injections in anaesthetised dogs. Equimolar intravenous injections of galanin (GAL) had no effect on cardiac vagal action in this species. Immunohistochemical analysis of dog stellate ganglia and cardiac muscle showed that most nerve cell bodies showing tyrosine hydroxylase immunoreactivity (TH-IR) also showed immunoreactivity to both NPY and GAL. The results are consistent with the proposal that NPY released from cardiac sympathetic nerves is responsible for the prolonged inhibition of cardiac vagal action known to be caused by such stimulation. A role for GAL, shown here to exist in cardiac sympathetic nerves in the dog, has yet to be determined.     

Evidence for a role of hydroxyl radical in immune-complex-induced vasculitis.

Previously it was shown that tissue injury occurring in acute immune-complex-induced vasculitis, which is complement and neutrophil-dependent, is significantly attenuated by the presence of catalase, suggesting the pathogenic role of H2O2 generated from activated neutrophils. We now show that significant protection is also afforded by pretreatment of animals with apolactoferrin , a naturally occurring chelator of iron. Iron-saturated lactoferrin is devoid of protective effects. Deferoxamine mesylate, a synthetic iron chelator, also has protective effects. Infusion of ionic iron, especially Fe(III), potentiates the tissue injury. Significant protection from tissue injury is also produced by treatment of rats with dimethyl sulfoxide, a potent hydroxyl radical scavenger. Morphologically, animals treated with these protective interventions show the influx of neutrophils into sites of immune complex deposition, but there is markedly attenuated edema, little or no hemorrhage, and little evidence of endothelial cell injury, in contrast to the findings in nonprotected animals. These data support the suggestion that immune-complex-induced injury may be linked to generation of H2O2 from activated neutrophils and the subsequent conversion of H2O2 to the hydroxyl radical.     

The distribution of dopamine-beta-hydroxylase, neuropeptide Y and galanin in locus coeruleus neurons

The locus coeruleus (LC) is composed of noradrenaline-producing neurons that project widely throughout the neuraxis. Subpopulations of LC neuron perikarya have been shown to contain neuropeptide Y (NPY) and galanin (GAL). In the major terminal fields of LC projections, the cerebral cortex, dorsal thalamus and cerebellar cortex, there are differing plexuses of dopamine-beta-hydroxylase (DBH), NPY and GAL immunoreactive axons. DBH immunoreactive plexuses are found in all areas which conform in appearance to previous demonstrations of noradrenaline localization by fluorescence histochemistry. In contrast, there are few NPY immunoreactive axons in thalamus and cerebellum, and the cortical plexus, while similar to the DBH immunoreactive plexus, is not affected by 6-hydroxydopamine treatment. Similarly, there are few GAL immunoreactive axons in either cerebral cortex, dorsal thalamus or cerebellar cortex. Transection of ascending LC axons results in accumulation of DBH but not NPY or GAL immunoreactivity proximal to the lesion. These observations indicate that NPY and GAL are distributed differently in LC neurons from noradrenaline and DBH.     

N-methyl-D-aspartate receptors in the medial septal area have a role in spatial and emotional learning in the rat

Cholinergic and GABAergic neurons in the medial septal/vertical limb of the diagonal band of Broca (MS/vDB) area project to the hippocampus and constitute the septohippocampal pathway, which has been implicated in learning and memory. There is also evidence for extrinsic and intrinsic glutamatergic neurons in the MS/vDB, which by regulating septohippocampal neurons can influence hippocampal functions. The potential role of glutamatergic N-methyl-D-aspartate (NMDA) receptors within the MS/vDB for spatial and emotional learning was studied using the water maze and step-through passive avoidance (PA) tasks, which are both hippocampal-dependent. Blockade of septal NMDA receptors by infusion of the competitive NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoic acid (D-AP5) (0.3-5 microg/rat), infused 15 min prior to training, impaired spatial learning and memory at the 5 microg dose of D-AP5, while doses of 0.3 and 1 microg per rat had no effect. The impairment in spatial learning appears not to be caused by sensorimotor or motivational disturbances, or anxiogenic-like behavior. Thus, d-AP5-treated rats were not impaired in swim performance or visuospatial abilities and spent more time in the open arms of the elevated plus-maze. In the PA task, intraseptal D-AP5 infused 15 min before training impaired retention as examined 24 h after training. This impairment was observed already at the 0.3 microg dose, suggesting that NMDA receptors within the MS/vDB may be more important for emotional than spatial memory. In summary, the present data indicate that changes in septal glutamate transmission and NMDA receptor activity can influence activity-dependent synaptic plasticity in the hippocampus and thereby learning and memory.     

Effects of haloperidol on the acquisition of a spatial learning task.

The effects of systemic injections of the dopaminergic antagonist haloperidol on the acquisition of the Morris water maze with either a visible or an invisible platform (nonspatial vs. spatial learning) were investigated. An open field test was used for selecting a dosage (< or = 0.1 mg/kg), that (hardly) affected locomotor behaviour. Differential effects were found. At 0.1 mg/kg, haloperidol reduced locomotion in the open field, impaired acquisition in the Morris maze with a visible platform, and blocked escape onto an invisible one. Even though 0.07 mg/kg haloperidol reduced locomotion, both 0.04 and 0.07 mg/kg only impaired Morris maze performance in the spatial version. A large effect was found in the first trial of every day's training block. These results indicate that haloperidol at low doses can lead to a moderate but significant impairment of spatial learning. It is suggested that the effects found are related to the function of the striatal areas in cue- and noncue-directed behaviour.     

The role of the entorhinal cortex in two forms of spatial learning and memory

It is generally acknowledged that the rodent hippocampus plays an important role in spatial learning and memory. The importance of the entorhinal cortex (ERC), an area that is closely interconnected anatomically with the hippocampus, in these forms of learning is less clear cut. Recent studies using selective, fibre-sparing cytotoxic lesions have generated conflicting results, with some studies showing that spatial learning can proceed normally without the ERC, suggesting that this area is not required for normal hippocampal function. The present study compared cytotoxic and aspiration ERC lesions with both fimbria fornix (FFX) lesions and sham-operated controls on two spatial learning tasks which have repeatedly been shown to depend on the hippocampus. Both groups of ERC lesions were impaired during non-matching-to-place testing (rewarded alternation) on the elevated T-maze. However, neither of these lesions subsequently had any effect on the acquisition of a standard spatial reference memory task in the water maze. FFX lesions produced a robust and reliable impairment on both of these tasks. A second experiment confirmed that cytotoxic ERC lesions spared water maze learning but disrupted rewarded alternation on the T-maze, when the order of behavioural testing was reversed. These results confirm previous reports that ERC-lesioned animals are capable of spatial navigation in the water maze, suggesting that the ERC is not a prerequisite for normal hippocampal function in this task. The present demonstration that ERC lesions disrupt non-matching-to-place performance may, however, be consistent with the possibility that ERC lesions affect attentional mechanisms, for example, by increasing the sensitivity to recent reward history.     

Evidence for the role of superoxide radicals in neutrophil-mediated cytotoxicity.

Human peripheral neutrophils became cytotoxic to chicken red blood cells (CRBC) in the presence of lectins as assessed by release of 51chromium from labelled target cells. Phytohaemagglutinin (PHA) and concanavalin A (Con A), which caused time-dependent and dose-dependent cytotoxicity over a concentration range of 25--400 microgram/ml, also caused significant generation of superoxide radicals as measured by ferricytochrome C reduction. Pokeweed mitogen, which does not induce cytotoxicity over the same concentration range, was unable to promote superoxide generation by neutrophils. PHA-induced generation of superoxide paralleled and appeared to precede PHA-dependent cytotoxicity. Superoxide dismutase (SOD), which enzymatically destroys superoxide, caused moderate inhibition of PHA-dependent cytotoxicity over the concentration range of 100--500 microgram/ml whereas catalytically inactive enzyme had no effect. Incubation under oxygen-depleted conditions caused a marked decrease in both PHA-induced superoxide generation and cytotoxicity relative to that obtained with neutrophils incubated aerobically. These findings suggest a central role for superoxide radicals in causing target cell damage in this model of neutrophil-mediated cytotoxicity.     

Evidence of a role for lactadherin in Alzheimer's disease

Lactadherin is a secreted extracellular matrix protein expressed in phagocytes and contributes to the removal of apoptotic cells. We examined lactadherin expression in brain sections of patients with or without Alzheimer's disease and studied its role in the phagocytosis of amyloid beta-peptide (Abeta). Cells involved in Alzheimer's disease, including vascular smooth muscle cells, astrocytes, and microglia, showed a time-related increase in lactadherin production in culture. Quantitative analysis of the level of lactadherin showed a 35% reduction in lactadherin mRNA expression in the brains of patients with Alzheimer's disease (n = 52) compared with age-matched controls (n = 58; P = 0.003). Interestingly, lactadherin protein was detected in the brains of patients with Alzheimer's disease and controls, with low expression in areas rich in senile plaques and marked expression in areas without Abeta deposition. Using surface plasmon resonance, we observed a direct protein-protein interaction between recombinant lactadherin and Abeta 1-42 peptide in vitro. Lactadherin deficiency or its neutralization using specific antibodies significantly prevented Abeta 1-42 phagocytosis by murine and human macrophages. In conclusion, lactadherin plays an important role in the phagocytosis of Abeta 1-42 peptide, and its expression is reduced in Alzheimer's disease. Alterations in lactadherin production/function may contribute to the initiation and/or progression of Alzheimer's disease.     

Evidence for a role of autoinflammation in early-phase psoriasis

Psoriasis is a common, inflammatory immune-mediated skin disease mainly presenting with plaques whose pathogenesis is based on the central role of the interleukin (IL)-23/IL-17 axis. However, the mechanisms acting in papular lesions of early-phase psoriasis are not fully understood. The aim of this study was to assess the involvement of autoinflammation, a state of sterile inflammation mainly driven by IL-1 over-production that has been recently hypothesized to act in the early phase of disease. Lesional skin of 10 patients with recent onset, untreated psoriasis has been investigated for expression of IL-1β, IL-17, IL-23 and other cytokines involved in the disease in comparison with normal skin of 10 healthy controls using a protein array method. Immunohistochemical phenotyping of inflammatory infiltrate and co-localization experiments with immunofluorescence confocal microscopy were conducted. IL-1β was significantly more expressed in psoriasis than in normal skin (P < 0·0001). The chemokine IL-8 was also over-expressed in psoriasis (P = 0·03) while IL-12, IL-17, IL-23, tumour necrosis factor-α and interferon-γ were only slightly more expressed in psoriasis than in normal skin, without reaching statistical significance. The inflammatory infiltrate consisted mainly of neutrophils with a relevant number of macrophages and dendritic cells and only scattered, predominantly T helper 1 lymphocytes. IL-1β co-localized mainly with CD66b, a neutrophil marker, suggesting that neutrophils were the major source of this cytokine. IL-1β over-expression in combination with low expression of cytokines that are predominant in late-phase plaque psoriasis may support the role of autoinflammation in early-phase disease, possibly paving the way to randomized trials with IL-1 antagonists.     

Relationship among leptin, neuropeptide Y, and galanin in young women and in postmenopausal women

OBJECTIVE: To determine whether hormonal status may affect neuropeptide Y (NPY), galanin, and leptin release in postmenopausal women and in young women. DESIGN: Forty-eight postmenopausal women aged 47-65 years and 35 young women aged 26-39 years were investigated. RESULTS: Plasma leptin concentrations increased with increasing body mass index in both young and postmenopausal women and were significantly higher in obese postmenopausal women than in obese young women (p < 0.01). Plasma NPY levels in obese young and postmenopausal women were significantly higher than in lean women (p < 0.01 and p < 0.01, respectively) and were significantly higher in obese and nonobese postmenopausal women than in young women (p < 0.05 and p < 0.001, respectively). Plasma galanin levels in postmenopausal women, both lean and overweight, were significantly lower than in young women (p < 0.01 andp < 0.01, respectively). In obese postmenopausal women, plasma galanin concentrations were lower without differing significantly from those in obese young women. However, they were significantly higher than that in lean postmenopausal women (p < 0.001). CONCLUSIONS: Our results suggest that the differences is plasma leptin, NPY, and galanin between postmenopausal women and young women may be related to body mass index rather than to differences in hormonal status and that the higher NPY levels in both lean and obese postmenopausal women than in young women indicate that factors other than body mass index may be involved.     

Instrumental learning within the spinal cord. II. Evidence for central mediation

Rats spinally transected at the second thoracic vertebra can learn to maintain their leg in a flexed position if they receive legshock for extending the limb. These rats display an increase in the duration of a flexion response that minimizes net shock exposure. The current set of experiments was designed to determine whether the acquisition of this behavioral response is mediated by the neurons of the spinal cord (i.e., is centrally mediated) or reflects a peripheral modification (e.g., a change in muscle tension). Experiment 1 found that preventing information from reaching the spinal cord by severing the sciatic nerve blocked the acquisition of this behavioral response. Spinalized rats also failed to learn if the spinal cord was anesthetized with lidocaine during exposure to response-contingent shock (Experiment 2). Experiment 3 demonstrated that prior exposure to response-contingent shock on one hindleg facilitated acquisition of the response when subjects were later tested on the opposite leg. These findings suggest that acquisition of the instrumental response depends on neurons within the spinal cord.     

Evidence that post-tetanic potentiation is mediated by neuropeptide release in Aplysia.

Many neuromuscular and central synapses exhibit activity-dependent plasticity. The sustained high-frequency firing needed to elicit some forms of plasticity are similar to those often required to release neuropeptides. We wanted to determine if neuropeptide release could contribute to post-tetanic potentiation (PTP) and chose neuromuscular synapses in buccal muscle I3a to explore this issue. This muscle is innervated by two motor neurons (termed B3 and B38) that show PTP in response to tetanic stimulation. B3 and B38 use glutamate as their fast transmitter but express different modulatory neuropeptides. B3 expresses FMRFamide, a neuropeptide that only slightly increases its own excitatory junction potentials (EJPs). B38 expresses the small cardioactive peptide (SCP), a neuropeptide that dramatically increases its own EJPs. It was our hypothesis that SCP released from B38's terminals during tetanic stimulation mediated a component of PTP for B38. Because no antagonist to SCP currently exists, we used several indirect approaches to test this hypothesis. First, we studied the effects of increasing stimulation frequency during the tetanus or lowering temperature on PTP. Both of these changes are known to dramatically increase SCP release. We found that increasing the frequency of stimulation increased PTP for both neurons; however, the effects were larger for B38. Decreasing the temperature tended to reduce PTP for B3, while increasing PTP for B38. These results were consistent with known properties of SCP release from B38. Next we selectively superfused the neuromuscular synapses with exogenous SCP to determine if this would occlude the effects of SCP released from B38 during a tetanus. We found that exogenous SCP dramatically reduced PTP for B38 but had little effect on PTP for B3. Thus our results support the hypothesis that physiological stimulation of B38 elicits PTP that is predominantly dependent on the release of SCP from its own terminals. They also demonstrate that the mechanisms underlying PTP can be very different for two motor neurons innervating the same target muscle.