Anatomy and biomechanics of gluteus maximus and the thoracolumbar fascia at the sacroiliac joint.

Biomechanical models predict that recruitment of gluteus maximus (GMax) will exert a compressive force across the sacroiliac joint (SIJ), yet this muscle requires morphologic assessment. The aims of this study were to document GMax's proximal attachments and assess their capacity to generate forces including compressive force at the SIJ. In 11 embalmed cadaver limbs, attachments of GMax crossing the SIJ were dissected and their fascicle orientation, length and attachment volume documented. The physiological cross-sectional area (PCSA) of each attachment was calculated along with its estimated maximum force at the SIJ and lumbar spine. GMax fascicles originated from the gluteus medius fascia, ilium, thoracolumbar fascia, erector spinae aponeurosis, sacrum, coccyx, dorsal sacroiliac and sacrotuberous ligaments in all specimens. Their mean fascicle orientation ranged from 32 to 45° below horizontal and mean length from 11 to 18 cm. The mean total PCSA of GMax was 26 cm(2) (range 16-36), of which 70% crossed the SIJ. The average maximum force predicted to be generated by GMax's total attachments crossing each SIJ was 891 N (range 572-1,215), of which 70% (702 N: range 450-1,009) could act perpendicular to the plane of the SIJ. The capacity of GMax to generate an extensor moment at lower lumbar segments was estimated at 4 Nm (range 2-9.5). GMax may generate compressive forces at the SIJ through its bony and fibrous attachments. These may assist effective load transfer between lower limbs and trunk.

alpha7 nicotinic acetylcholine receptor agonist properties of tilorone and related tricyclic analogues.

BACKGROUND AND PURPOSE: The alpha7 nicotinic acetylcholine receptor (nAChR) has attracted considerable interest as a target for cognitive enhancement in schizophrenia and Alzheimer's Disease. However, most recently described alpha7 agonists are derived from the quinuclidine structural class. Alternatively, the present study identifies tilorone as a novel alpha7-selective agonist and characterizes analogues developed from this lead. EXPERIMENTAL APPROACH: Activity and selectivity were determined from rat brain alpha7 and alpha4beta2 nAChR binding, recombinant nAChR activation, and native alpha7 nAChR mediated stimulation of ERK1/2 phosphorylation in PC12 cells. KEY RESULTS: Tilorone bound alpha7 nAChR (IC(50) 110 nM) with high selectivity relative to alpha4beta2 (IC(50) 70 000 nM), activated human alpha7 nAChR with an EC(50) value of 2.5 microM and maximal response of 67% relative to acetylcholine, and showed little agonist effect at human alpha3beta4 or alpha4beta2 nAChRs. However, the rat alpha7 nAChR maximal response was only 34%. Lead optimization led to 2-(5-methyl-hexahydro-pyrrolo[3,4-c]pyrrol-2-yl)-xanthen-9-one (A-844606) with improved binding (alpha7 IC(50) 11 nM, alpha4beta2 IC(50)>30 000 nM) and activity at both human and rat alpha7 nAChR (EC(50)s 1.4 and 2.2 microM and apparent efficacies 61 and 63%, respectively). These compounds also activated native alpha7 nAChR, stimulating ERK1/2 phosphorylation in PC12 cells. CONCLUSIONS AND IMPLICATIONS: Tilorone, known as an interferon inducer, is a selective alpha7 nAChR agonist, suggesting utility of the fluorenone pharmacophore for the development of alpha7 nAChR selective agonists. Whether alpha7 stimulation mediates interferon induction, or whether interferon induction may influence the potential anti-inflammatory properties of alpha7 nAChR agonists remains to be elucidated.

Fly pupae and puparia as potential contaminants of forensic entomology samples from sites of body discovery.

Fly pupae and puparia may contaminate forensic entomology samples at death scenes if they have originated not from human remains but from animal carcasses or other decomposing organic material. These contaminants may erroneously lengthen post-mortem interval estimates if no pupae or puparia are genuinely associated with the body. Three forensic entomology case studies are presented, in which contamination either occurred or was suspected. In the first case, blow fly puparia collected near the body were detected as contaminants because the species was inactive both when the body was found and when the deceased was last sighted reliably. The second case illustrates that contamination may be suspected at particularly squalid death scenes because of the likely presence of carcasses or organic material. The third case involves the presence at the body discovery site of numerous potentially contaminating animal carcasses. Soil samples were taken along transects to show that pupae and puparia were clustered around their probable sources.

Social isolation and delayed discovery of bodies in houses: the value of forensic pathology, anthropology, odontology and entomology in the medico-legal investigation.

The bodies of socially isolated people may remain undiscovered in their own houses for prolonged periods. Occasionally the body is in situ for sufficient time to become skeletonised, or partially so. Medico-legal investigation of these cases is complicated by degradation and contamination of evidence. Thus, a multidisciplinary forensic investigation is recommended. The potential contributions of forensic pathology, anthropology, odontology and entomology are outlined here with reference to two cases that occurred in Victoria, Australia, in 2003. Forensic pathologists are often unable to determine the cause of death in skeletonised bodies, however, they may find evidence to support either a natural or unnatural mode of death, and they may describe skeletal pathology or trauma, and identify skeletal features to support radiological identification of the deceased. Anthropologists can provide supplementary evidence of skeletal trauma. Additionally, they can assess age, sex, stature and racial affiliation from skeletal remains. Odontologists can identify individuals through comparison with ante-mortem dental records; however, potential difficulties exist in identifying the treating dentist of a socially isolated person. Odontologists may also examine the teeth and oro-facial skeleton for trauma. Entomologists may estimate minimum death time and/or season of death. Entomological examination of insect remains may also confirm that a body has lain in situ for a considerable period.

Histology of the fascial-periosteal interface in lower limb chronic deep posterior compartment syndrome.

OBJECTIVE: To describe the histological features of the fascial-periosteal interface at the medial tibial border of patients surgically treated for chronic deep posterior compartment syndrome and to make statistical comparisons with control tissue. METHODS: Nineteen subjects and 11 controls were recruited. Subject tissue was obtained at operation, and control tissue from autopsy cases. Tissue samples underwent histological preparation and then examination by an independent pathologist. Samples were analysed with regard to six histological variables: fibroblastic activity, chronic inflammatory cells, vascularity, collagen regularity, mononuclear cells, and ground substance. Collagen regularity was measured with respect to collagen density, fibre arrangement, orientation, and spacing. The observed changes were graded from 1 to 4 in terms of abnormality. Mann-Whitney U test, Spearman correlation coefficients, and intraobserver reliability scores were used. RESULTS: With regard to collagen arrangement, control tissue showed greater degrees of irregularity than subject tissue (p = 0.01). Subjects with a symptom duration of greater than 12 months (as opposed to less than 12 months) showed greater degrees of collagen irregularity (p = 0.043). Vascular changes approached significance (p = 0.077). With regard to the amount of fibrocyte activity, chronic inflammatory cell activity, mononuclear cells, or ground substance, there were no significant differences between controls and subjects. Good correlation was seen in scores measuring chronic inflammatory cell activity and mononuclear cells (r = 0.649), and moderate correlation was seen between fibrocyte activity and vascular changes (r = 0.574). Intraobserver reliability scores were good for chronic inflammatory cell activity and moderate for vascular changes, but were poor for collagen and fibrocyte variables. Individual cases showed varying degrees of fibrocyte activity, chronic inflammatory cellular infiltration, vascular abnormalities, and collagen fibre disruption. CONCLUSIONS: Statistical analysis showed no histological differences at the fascial-periosteal interface in cases of chronic deep posterior compartment syndrome, except for collagen, which showed less irregularity in subject samples. The latter may indicate a remodelling process, and this is supported by greater collagen irregularity in subjects with longer duration of symptoms.

Segmental degeneration in the cervical spine and associated changes in dorsal root ganglia.

Degenerative change in cervical segments C5-C7 was documented to determine whether osteo-ligamentous adaptations were age-related. In addition, companion morphological studies were carried out to determine whether parallel changes occurred in related soft tissues, including DRG. Independent of the provoking stimulus, aberrant soft tissue change may be expected with segmental degeneration. Two associations were identified: between the incidence of segmental degeneration and severity of DRG distortion, and between segmental degeneration and DRG inflammatory mast cell density. Peripheral type C cells seemed more susceptible to compression in circumstances of DRG distortion. In light of neuropeptide expression in these cell types, predominant type C cell compression may be clinically relevant in the noxious cascade contributing to the sensation of pain.

Muscle spindle distribution, morphology, and density in longus colli and multifidus muscles of the cervical spine.

STUDY DESIGN: Tissue blocks comprising muscle and bone from C5 to C7 segments were harvested at autopsy from 16 individuals ranging in age from 4 to 77 years. The prevertebral longus colli and postvertebral multifidus muscle pairs from one side in each individual were randomly selected for this study of muscle spindles. OBJECTIVES: To determine muscle spindle distribution, morphology, and density for the longus colli and multifidus in caudal segments of the human cervical spine, and to assess whether changes are evident from infancy to old age. SUMMARY OF BACKGROUND DATA: Age-related changes to the osteoligamentous framework of the cervical spine have been well documented. Postural modification accompanies these structural alterations, but there have been limited attempts to document whether muscle sustains a comparable level of morphologic alteration. Previous studies have examined muscle spindles in the neck muscles of various animal models and in a variety of isolated human muscles. However, most of these studies incurred bias through sampling and methodologic assumptions. METHODS: The longus colli and multifidus were resected between C5 and C7, and between left and right pairs selected randomly for spindle analysis. These vertebral segments were selected deliberately because they form the apex of the cervical lordosis and the site at which the greatest age-related modification occurs. The tissue was processed in paraffin, sectioned, and then stained by Masson's trichrome. Spindle characteristics were examined using light microscopy and analyzed by unbiased stereologic methods. A one-sample paired t test was used to ascertain whether the differences in spindle density between the two muscles were statistically significant. RESULTS: The longus colli has a high density of muscle spindles, which appear clustered and concentrated anterolaterally, away from the vertebral body. The multifidus has a low density of muscle spindles, which are found predominantly as single units concentrated closely to the vertebral lamina. No change in spindle distribution, morphology, and density were observed with age. CONCLUSIONS: The current study examined spindle characteristics for an intrinsic neck muscle pair whose coactivation contributes to segmental stability of the cervical spine. The distribution and morphology of muscle spindles differ between the longus colli and the multifidus. In addition, these muscles have significant differences in terms of mean spindle density. Spindle characteristics represent one of many factors that govern proprioceptive regulation in skeletal muscle, and in neck muscles, the central connectivity of these receptors remains undefined. Therefore, although there are anatomic differences between the neck flexor and extensor, the functional implications of these differences are not clear. It is also of interest that spindle characteristics remain unchanged in these intrinsic muscles whose underlying segments are subject to age-related osteoligamentous changes.

Epibatidine, a nicotinic acetylcholine receptor agonist, inhibits the capsaicin response in dorsal root ganglion neurons.

In patch-clamp recordings from small-medium diameter dorsal root ganglion neurons in culture, (+/-)-epibatidine (1 microM) was able to inhibit the capsaicin response (IC(50)=0.32 microM) in neurons where there was no detectable direct nicotinic response. Thus, (+/-)-epibatidine may inhibit the vanilloid receptor in a manner that is not dependent upon nicotinic current activation, representing another mechanism by which such ligands could modulate vanilloid receptor signaling.

Comparative histochemical composition of muscle fibres in a pre- and a postvertebral muscle of the cervical spine.

References to histochemistry are extensive for human limb muscles but occur less frequently in relation to vertebral muscle. Most vertebral muscle literature has been concerned with muscle fibre characteristics in the lumbar and thoracic spine, due in large part to the incidence of low back pain and idiopathic scoliosis. However few studies have investigated the histochemical composition of neck muscles in humans: and, to our knowledge, no previous study has examined the antagonistic longus colli and multifidus muscle pair. In addition, while age-related segmental degeneration is most prominent between C5 and C7, it is not known whether these osteoligamentous changes are paralleled by changes in muscle fibre ratio. Tissue blocks comprising muscle and bone from C5-C7 segments were harvested at autopsy from 16 subjects with ages ranging from 4 to 77 years. The prevertebral longus colli and postvertebral multifidus muscle pairs were randomly selected from one or other side in each subject. The tissue was frozen, sectioned and histochemically stained for myofibrillar adenosine triphosphatase. Analysis of muscle fibre types was performed by light microscopy. Wilcoxon paired t-tests were used to ascertain whether intramuscular and intermuscular differences in fibre composition were significant. In addition, correlation and regression analyses were used to determine whether fibre type proportions changed in either muscle with increasing age. The present study has revealed histochemical differences between longus colli and multifidus at the level of the C5-C7 vertebral segments. Multifidus comprises a significantly greater proportion of type I than type II fibres. Longus colli comprises a significantly greater proportion of type II fibres than multifidus. Further there were no changes in fibre type proportion in either muscle with increasing age. These observations suggest that longus colli responds equally to postural and phasic demands, whereas multifidus is predominantly postural. Also it would appear that age-related structural alterations in lower cervical segments are not paralleled by changes in muscle fibre ratio.

Monitoring age-related changes of collagen content and vascularity in ganglia using unbiased stereological methods.

We describe for the first time application of unbiased stereological techniques to estimate total volume and volume fractions of interest in individual dorsal root ganglia (DRG). Volume estimates were obtained using a two-stage sampling design. Sections were systematically sampled following a random start, from DRG which were embedded in methacrylate and exhaustively sectioned. We further examined the efficiency of point counting irregular volume fractions housed in a regular reference volume. We found that the precision of volume estimates was relatively unaffected by exhaustive sampling, and that the magnitude of error was, in large part, determined by object shape.

Attachments of the posterior layer of lumbar fascia.

STUDY DESIGN: Superficial and deep laminae of the posterior layer of lumbar fascia were dissected. The lumbar portion was measured for evidence of segmental thickenings. Superior attachments were dissected, documented, and photographed. OBJECTIVES: To verify the existence of posterior accessory ligaments and establish the superior attachments and fiber angles of the posterior layer of lumbar fascia. SUMMARY OF BACKGROUND DATA: There have been two small dissection studies on the posterior layer. Their findings are conflicting in several areas of clinical significance. Thickenings in the lumbar region were described in one study, but have not been verified. The superior attachments of the posterior layer have not been formally documented. METHODS: Study 1: In 21 embalmed cadavers, the lumbar region of the posterior layer was dissected. The lumbar spinous processes and adjacent fascia were marked. The fascia was removed and examined, and its thickness measured with a manual micrometer. Results were statistically analyzed. Study 2: Superior attachments of the posterior layer in 20 cadavers were dissected and photographed. Capacity to transmit tension was estimated and documented photographically, and fiber angles measured in situ. RESULTS: Study 1: There was no evidence of macroscopic segmental thickening in the posterior layer. Study 2: The superficial lamina was continuous superiorly with the rhomboids, and the deep lamina with the tendons of splenius cervices and capitis. These previously undocumented attachments were of variable thickness and fibrosity, and capable of transmitting tension. CONCLUSIONS: Both superficial and deep laminae of the posterior layer are more extensive superiorly than previously thought. This may have implications for certain tests used in assessment and management of low back pain such as the slump and "nonorganic" tests. The thickness of the superior attachments is variable. Their capacity for load bearing is yet to be quantified.

Gain of function mutation of the alpha7 nicotinic receptor: distinct pharmacology of the human alpha7V274T variant.

In the human alpha7 nicotinic receptor, valine-274 in the pore-lining transmembrane-2 region was mutated to threonine to produce the variant human alpha7V274T, which was evaluated electrophysiologically following expression in Xenopus laevis oocytes. Inward current rectification was strong in human alpha7V274T as in the human alpha7 wild type nicotinic receptor. However, human alpha7V274T was 100-fold more sensitive to the nicotinic receptor agonists acetylcholine, (-)-nicotine and 1,1-dimethyl-4-phenylpiperazinium. Choline also activated human alpha7V274T (EC50 = 12 microM) and was 82-fold more potent than at human alpha7 wild type nicotinic receptor. (-)-Cotinine, (2,4)-dimethoxybenzylidene anabaseine (GTS-21) and 2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine (ABT-089), weak partial agonists at human alpha7 wild type, were much stronger agonists at human alpha7V274T with EC50 values of 70 microM, 4 microM and 28 microM and fractional activation values of 93%, 96% and 40%, respectively. However, (-)-lobeline, a human alpha7 wild type nicotinic receptor antagonist, and dihydro-beta-erythroidine, which activates chick mutagenized alpha7 nicotinic receptors, had only weak agonist-like activity at human alpha7V274T (< or = 4% of the maximal acetylcholine response). Methyllycaconitine, mecamylamine, d-tubocurarine and dihydro-beta-erythroidine retained antagonist activity and, indeed, appeared to be at least as potent at human alpha7V274T as at human alpha7 wild type. These results support and extend the concept that human nicotinic receptor pharmacology can be profoundly altered by single amino acid changes in the pore-lining segment.

Activation and inhibition of the human alpha7 nicotinic acetylcholine receptor by agonists.

To better understand the effects of weak as well as strong agonists at the human alpha7 nicotinic acetylcholine receptor (human alpha7 nAChR), the abilities of several classic nAChR agonists to both activate and inhibit (desensitize) the human alpha7 nAChR expressed in Xenopus oocytes were quantified and compared. Activation was measured during 0.2-20 s agonist application, as required to elicit a peak response. Inhibition was measured as the reduction in the agonist response to 200 microM ACh in the presence of inhibitor during a 5-20 min incubation. Acetylcholine (ACh), (-)-nicotine, (+)-nicotine, and 1,1-dimethyl-4-phenylpiperazinium (DMPP) were 62- to 130-fold more potent as inhibitors than as activators, with excellent correlation between the IC50 and EC50 values (r2 = 0.924). Agonist concentrations that elicited only 0.6-1.2% nAChR activation were sufficient to inhibit the response to ACh by 50%. Thus, even a very weak agonist could appear to be a potent and effective inhibitor through receptor desensitization. (-)-Lobeline, in contrast, acted as an antagonist at the human alpha7 nAChR, eliciting no detectable agonist-like response at concentrations up to 1 mM, but inhibiting the response to ACh with an IC50 value of 8.5 microM. (-)-Cotinine and the novel ligand ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine] acted as weak agonists at the human alpha7 nAChR (1 and 1.5% response at 1 mM, respectively) and inhibited the response to ACh with IC50) values of 175 and 48 microM, respectively. These effects could be explained by receptor desensitization, at least in part.

The role of neuronal nicotinic acetylcholine receptors in antinociception: effects of ABT-594.

ABT-594, a nicotinic acetylcholine receptor agonist, has antinociceptive effects in rat models of acute thermal, persistent chemical, and neuropathic pain. Direct injection of ABT-594 into the nucleus raphe magnus (NRM) is antinociceptive in a thermal threshold test and destruction of serotonergic neurons in the NRM attenuates the effect of systemic ABT-594. However, lidocaine-inactivation of the NRM prevents the antinociceptive effect of systemic (-)-nicotine but not that of systemic ABT-594.

Disc herniations in the young and end-plate vascularity.

The objective of this study was to determine the nature of the persistence of remnants of the original nutritive vascular canals within the vertebral body and correlate their existence with end-plate "weak spots." The body-disc region of 20 lumbar vertebrae between the ages of birth and 22 years was examined histologically to study the vascularity of the end-plate cartilage and its fate at the end of vertebral growth. Observations indicate a regression of the vascular canals in the end-plate commencing in the first decade, with "scars" left by these canals visible as nodular areas. By the beginning of the third decade, herniation of the disc material into the weak spots was observed. It is apparent that these weak spots represent a route for the early formation of intrabody nuclear herniations at this age (Schmorl's nodes).

ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine]: a novel, orally effective analgesic acting via neuronal nicotinic acetylcholine receptors: I. In vitro characterization.

The discovery of (+/-)-epibatidine, a naturally occurring neuronal nicotinic acetylcholine receptor (nAChR) agonist with antinociceptive activity 200-fold more potent than that of morphine, has renewed interest in the potential role of nAChRs in pain processing. However, (+/-)-epibatidine has significant side-effect liabilities associated with potent activity at the ganglionic and neuromuscular junction nAChR subtypes which limit its potential as a clinical entity. ABT-594 [(R)-5-(2-azetidinylmethoxy)-2-chloropyridine] is a novel, potent cholinergic nAChR ligand with analgesic properties (see accompanying paper by Bannon et al., 1998b) that shows preferential selectivity for neuronal nAChRs and a consequently improved in vivo side-effect profile compared with (+/-)-epibatidine. ABT-594 is a potent inhibitor of the binding of [3H](-)-cytisine to alpha 4 beta 2 neuronal nAChRs (Ki = 37 pM, rat brain; Ki = 55 pM, transfected human receptor). At the alpha 1 beta 1 delta gamma neuromuscular nAChR labeled by [125I] alpha-bungarotoxin (alpha-Btx), ABT-594 has a Ki value of 10,000 nM resulting in a greater than 180,000-fold selectivity of the compound for the neuronal alpha 4 beta 2 nAChR. In contrast, (+/-)-epibatidine has Ki values of 70 pM and 2.7 nM at the alpha 4 beta 2 and alpha 1 beta 1 delta gamma nAChRs, respectively, giving a selectivity of only 38-fold. The S-enantiomer of ABT-594, A-98593 has activity at the neuronal alpha 4 beta 2 nAChR identical with ABT-594 (Ki = 34-39 pM), which demonstrates a lack of stereospecific binding similar to that reported previously for (+/-)-epibatidine. A similar lack of stereoselectivity is seen at the human alpha 7 receptor. However, A-98593 is 3-fold more potent at the neuromuscular nAChR (Ki = 3420 nM) and the brain alpha-Btx-sensitive nAChR (Ki = 4620 nM) than ABT-594. ABT-594 has weak affinity in binding assays for adrenoreceptor subtypes alpha-1B (Ki = 890 nM), alpha-2B (Ki = 597 nM) and alpha-2C (Ki = 342 nM), and it has negligible affinity (Ki > 1000 nM) for approximately 70 other receptors, enzyme and transporter binding sites. Functionally, ABT-594 is an agonist. At the transfected human alpha 4 beta 2 neuronal nAChR (K177 cells), with increased 86Rb+ efflux as a measure of cation efflux, ABT-594 had an EC50 value of 140 nM with an intrinsic activity (IA) compared with (-)-nicotine of 130%; at the nAChR subtype expressed in IMR-32 cells (sympathetic ganglion-like), an EC50 of 340 nM (IA = 126%); at the F11 dorsal root ganglion cell line (sensory ganglion-like), an EC50 of 1220 nM (IA = 71%); and via direct measurement of ion currents, an EC50 value of 56,000 nM (IA = 83%) at the human alpha 7 homooligimeric nAChR produced in oocytes. A-98593 is 2- to 3-fold more potent and displays approximately 50% greater intrinsic activity than ABT-594 in all four functional assays. In terms of potency, ABT-594 is 8- to 64-fold less active than (+/-)-epibatidine and also has less IA in these functional assays. ABT-594 (30 microM) inhibits the release of calcitonin gene-related peptide from C-fibers terminating in the dorsal horn of the spinal cord, an effect mediated via nAChRs. Pharmacologically, ABT-594 has an in vitro profile distinct from that of the prototypic nicotinic analgesic (+/-)-epibatidine, with the potential for substantially reduced side-effect liability and, as such, represents a potentially novel therapeutic approach to pain management.

Identification and initial structure-activity relationships of (R)-5-(2-azetidinylmethoxy)-2-chloropyridine (ABT-594), a potent, orally active, non-opiate analgesic agent acting via neuronal nicotinic acetylcholine receptors.

New members of a previously reported series of 3-pyridyl ether compounds are disclosed as novel, potent analgesic agents acting through neuronal nicotinic acetylcholine receptors. Both (R)-2-chloro-5-(2-azetidinylmethoxy)pyridine (ABT-594, 5) and its S-enantiomer (4) show potent analgesic activity in the mouse hot-plate assay following either intraperitoneal (i.p.) or oral (p.o.) administration, as well as activity in the mouse abdominal constriction (writhing) assay, a model of persistent pain. Compared to the S-enantiomer and to the prototypical potent nicotinic analgesic agent (+/-)-epibatidine, 5 shows diminished activity in models of peripheral side effects. Structure-activity studies of analogues related to 4 and 5 suggest that the N-unsubstituted azetidine moiety and the 2-chloro substituent on the pyridine ring are important contributors to potent analgesic activity.

ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine]: I. A potent and selective cholinergic channel modulator with neuroprotective properties.

Accumulating preclinical and clinical evidence data suggests that compounds that selectively activate neuronal nicotinic acetylcholine receptor (nAChR) subtypes may have therapeutic utility for the treatment of several neurological disorders. In the present study, the in vitro pharmacological properties of the novel cholinergic channel modulator ABT-089 [2-methyl-3-(2-(S)-pyrrolidinylmethoxy)pyridine], are described. In radioligand binding studies, ABT-089 was shown to display selectivity toward the high-affinity (-)-cytisine binding site present on the alpha4beta2 nAChR subtype (Ki = 16 nM) relative to the [125I]alpha-bungarotoxin binding site present on the alpha7 (Ki > or = 10,000 nM) and alpha1beta1deltagamma (Ki > 1000 nM) nAChR subtypes. In cation flux and channel current studies, ABT-089 displayed a more complex profile than (-)-nicotine having agonist, partial agonist and inhibitory activities depending on the nAChR subtype with which it interacts. ABT-089 differentially stimulated neurotransmitter release. The compound displayed a similar potency and efficacy to (-)-nicotine to facilitate ACh release (ABT-089, EC50 = 3 microM; (-)-nicotine, EC50 = 1 microM), but was markedly less potent and less efficacious than (-)-nicotine to stimulate dopamine release (ABT-089, EC50 = 1.1 microM; (-)-nicotine, EC50 = 0.04 microM). Additionally, ABT-089 was neuroprotective against the excitotoxic insults elicited by exposure to glutamate in both rat cortical cell cultures (EC50 = 10 +/- 3 microM) and differentiated human IMR32 cells (EC50 = 3 +/- 2 microM). The differential full agonist/partial agonist profile of ABT-089, as compared with (-)-nicotine and ABT-418, illustrates the complexity of nAChR activation and the potential to target responses at subclasses of the neuronal and peripheral receptors.

Functional characterization of the novel neuronal nicotinic acetylcholine receptor ligand GTS-21 in vitro and in vivo.

(2.4)-Dimethoxybenzylidene anabaseine dihydrochloride (GTS-21), a compound that interacts with rat neuronal nicotinic acetylcholine receptors (nAChRs), was evaluated using human recombinant nAChRs in vitro and various pharmacokinetic and behavioral models in rodents, dogs and monkeys. GTS-21 bound to human alpha 4 beta 2 nAChR (K1-20 nM) 100-fold more potently than to human alpha 7 nAChR, and was 18- and 2-fold less potent than (-)-nicotine at human alpha 4 beta 2 and alpha 7 nAChR, respectively. Functionally. GTS-21 stimulated [5H]dopamine release from rat striatal slices with an EC50 of 10 +/- 2 microM (250-fold less potent and 70% as efficacious as (-)-nicotine), an effect blocked by the nAChR antagonist dihydro-beta-erythroidine. However, GTS-21 did not stimulate human alpha 4 beta 2 nor human ganglionic nAChRs significantly. In vivo, GTS-21 had no adverse effect on dog blood pressure (< or = 2.5 micromol/kg i.v. bolus infusion), in marked contrast with (-)-nicotine, GTS-21 (-62 micromol/kg.s.e.) also did not cross-discriminate significantly with (-)-nicotine in rats and did not reduce temperature or locomotion in mice. Neither was it active in the elevated plus maze anxiety model (0.19-6.2 micromol/kg.IP) in normal mice. However, GTS-21 did improve learning performance of monkeys in the delayed matching-to-sample task (32-130 nmol/kg.i.m.).

Relationship between the cervical component of the slump test and change in hamstring muscle tension.

SUMMARY. The slump test has been used routinely to differentiate low back pain due to involvement of neural structures from low back pain attributable to other factors. It is also said to differentiate between posterior thigh pain due to neural involvement from that due to hamstring injury. If changes in cervical position affect the hamstring muscles, differential diagnosis is confounded. Posterior thigh pain caused by the cervical component of the slump could then be caused either by increased tension on neural structures or increased tension in the hamstrings themselves. The aim of this study was to determine whether changing the cervical position during slump altered posterior thigh pain and/or the tension in the hamstring muscle. Asymptomatic subjects aged between 18 and 30 years were tested. A special fixation device was engineered to fix the trunk, pelvis and lower limb. Pain levels in cervical flexion and extension were assessed by visual analogue scale. Fixation was successful in that there were no significant differences in position of the pelvis or knee during changes in cervical position. Averaged over the group, there was a 40% decrease (P < 0.05) in posterior thigh pain with cervical extension. There were no significant differences in hamstring electromyographic readings during the cervical movements. This indicated that: (1) cervical movement did not change hamstring muscle tension, and (2) the change in experimentally induced pain during cervical flexion was not due to changes in the hamstring muscle. This conclusion supports the view that posterior thigh pain caused by the slump test and relieved by cervical extension arises from neural structures rather than the hamstring muscle. Copyright 1997 Harcourt Publishers Ltd.