Procedural pain of an ultrasound-guided brachial plexus block: a comparison of axillary and infraclavicular approaches.

BACKGROUND: Ultrasound (US)-guided infraclavicular (IC) and axillary (AX) blocks have similar effectiveness. Therefore, limiting procedural pain may help to choose a standard approach. The primary aims of this randomized study were to assess patient's pain during the block and to recognize its cause. METHODS: Eighty patients were randomly allocated to the IC or the AX group. A blinded investigator asked the patients to quantify block pain on a Visual Analogue Scale (VAS 0-100) and to indicate the most unpleasant component (needle passes, paraesthesie or local anaesthetics injection). Sensory block was assessed every 10 min. After 30 min, the unblocked nerves were supplemented. Patients were ready for surgery when they had analgesia or anaesthesia of the five nerves distal to the elbow. Preliminary scan time, block performance and latency times, readiness for surgery, adverse events and patient's acceptance were recorded. RESULTS: The axillary approach resulted in lower maximum VAS scores (median 12) than the infraclavicular approach (median 21). This difference was not statistically significant (P=0.07). Numbers of patients indicating the most painful component were similar in both groups. Patients in either group were ready for surgery after 25 min. Two patients in the IC group and seven in the AX group needed block supplementation (n.s.). Block performance times and number of needle passes were significantly lower in the IC group. Patients' acceptance was 98% in both groups. CONCLUSIONS: We did not find significant differences between the two approaches in procedural pain and patient's acceptance. The choice of approach may depend on the anaesthesiologist's experience and the patient's preferences.

GABA(B) and NMDA receptors contribute to spindle-like oscillations in rat thalamus in vitro.

Thalamic slice preparations, in which intrathalamic connectivity between the reticular nucleus and relay nuclei is maintained, are capable of sustaining rhythmic burst firing activity in rodents and ferret. These in vitro oscillations occur spontaneously in the ferret and have frequencies (6-10 Hz) within the range of sleep spindles observed in vivo. In the rat, mainly lower frequency (2-4 Hz) oscillations, evoked under conditions of low bath [Mg(2+)] and/or GABA(A) receptor blockade, have been described. Here we show that faster rhythms in the range of 4-9 Hz can be evoked in rat thalamic slices by electrical stimulation of the internal capsule and also occur spontaneously. When bath [Mg(2+)] was 2 mM, these spindle-like oscillations were most common in a brief developmental time window, peaking at postnatal day 12 (P12). The oscillations were almost completely blocked by the GABA(A) receptor antagonist picrotoxin, and, in some cases, the frequency of oscillations was increased by the GABA(B) receptor antagonist CGP-35348. The selective blockade of N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors by the antagonists 2-amino-5-phosphonovaleric acid or 1,2,3,4-Tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX), respectively, significantly shortened oscillations but did not completely block them. A combination of the two drugs was necessary to abolish oscillatory activity. The barbituate pentobarbital, which enhances GABA(A)R responses, initially slowed and synchronized oscillations before completely blocking them. When bath [Mg(2+)] was reduced from 2 to 0.65 mM, evoked oscillations became more robust and were often accompanied by spontaneously arising oscillations. Under these conditions, GABA(A) receptor blockade no longer inhibited oscillations, but instead converted them into the slow, synchronous rhythms that have been observed in other studies. The effects of GABA(B) or NMDA receptor blockade were more pronounced in 0.65 mM than in 2 mM external [Mg(2+)]. Thus spindle-like oscillations occur in rat thalamic slices in vitro, and we find that, in addition to the previously demonstrated contributions of GABA(A) and AMPA receptors to these oscillations, NMDA and GABA(B) receptors are also involved. The strong influence of external [Mg(2+)] on GABAergic pharmacology and a contribution of NMDA receptors during oscillations suggest a link between the excitability of NMDA receptors and the activation of GABA(B)R-mediated inhibitory postsynaptic currents.

Single amino acid substitutions in kappa-conotoxin PVIIA disrupt interaction with the shaker K+ channel.

kappa-Conotoxin PVIIA (kappa-PVIIA), a 27-amino acid peptide with three disulfide cross-links, isolated from the venom of Conus purpurascens, is the first conopeptide shown to inhibit the Shaker K(+) channel (Terlau, H., Shon, K., Grilley, M., Stocker, M., Stühmer, W., and Olivera, B. M. (1996) Nature 381, 148-151). Recently, two groups independently determined the solution structure for kappa-PVIIA using NMR; although the structures reported were similar, two mutually exclusive models for the interaction of the peptide with the Shaker channel were proposed. We carried out a structure/function analysis of kappa-PVIIA, with alanine substitutions for all amino acids postulated to be key residues by both groups. Our data are consistent with the critical dyad model developed by Ménez and co-workers (Dauplais, M., Lecoq, A., Song, J. , Cotton, J., Jamin, N., Gilquin, B., Roumestand, C., Vita, C., de Medeiros, C., Rowan, E. G., Harvey, A. L., and Ménez, A. (1997) J. Biol. Chem. 272, 4802-4809) for polypeptide antagonists of K(+) channels. In the case of kappa-PVIIA, Lys(7) and Phe(9) are essential for activity as predicted by Savarin et al. (Savarin, P., Guenneugues, M., Gilquin, B., Lamthanh, H., Gasparini, S., Zinn-Justin, S., and Ménez, A. (1998) Biochemistry 37, 5407-5416); these workers also correctly predicted an important role for Lys(25). Thus, although kappa-conotoxin PVIIA has no obvious sequence homology to polypeptide toxins from other venomous animals that interact with voltage-gated K(+) channels, there may be convergent functional features in diverse K(+) channel polypeptide antagonists.

A resource model of the neural basis of executive working memory.

Working memory (WM) refers to the temporary storage and processing of goal-relevant information. WM is thought to include domain-specific short-term memory stores and executive processes, such as coordination, that operate on the contents of WM. To examine the neural substrates of coordination, we acquired functional magnetic resonance imaging data while subjects performed a WM span test designed specifically to measure executive WM. Subjects performed two tasks (sentence reading and short-term memory for five words) either separately or concurrently. Dual-task performance activated frontal-lobe areas to a greater extent than performance of either task in isolation, but no new area was activated beyond those activated by either component task. These findings support a resource theory of WM executive processes in the frontal lobes.

The T-superfamily of conotoxins.

We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (- -CC- -CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCPKQMRCCTL*; tx5a, gammaCCgammaDGW(+)CCT( section sign)AAO; and au5a, FCCPFIRYCCW (where gamma = gamma-carboxyglutamate, W(+) = bromotryptophan, O = hydroxyproline, T( section sign) = glycosylated threonine, and * = COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional gamma-carboxylation recognition signal in the -1 to -20 propeptide region, consistent with the presence of gamma-carboxyglutamate residues in this peptide.

Critical residues influence the affinity and selectivity of alpha-conotoxin MI for nicotinic acetylcholine receptors.

The mammalian skeletal muscle acetylcholine receptor contains two nonequivalent acetylcholine binding sites, one each at the alpha/delta and alpha/gamma subunit interfaces. Alpha-Conotoxin MI, a 14-amino acid competitive antagonist, binds at both interfaces but has approximately 10(4) higher affinity for the alpha/delta site. We performed an "alanine walk" to identify the residues in alpha-MI that contribute to this selective interaction with the alpha/delta site. Electrophysiological measurements with Xenopus oocytes expressing normal receptors or receptors lacking either the gamma or delta subunit were made to assay toxin-receptor interaction. Alanine substitutions in most amino acid positions had only modest effects on toxin potency at either binding site. However, substitutions in two positions, proline-6 and tyrosine-12, dramatically reduced toxin potency at the high-affinity alpha/delta site while having comparatively little effect on low-affinity alpha/gamma binding. When tyrosine-12 was replaced by alanine, the toxin's selectivity for the high-affinity site (relative to that for the low-affinity site) was reduced from 45,000- to 30-fold. A series of additional amino acid substitutions in this position showed that increasing side chain size/hydrophobicity increases toxin potency at the alpha/delta site without affecting alpha/gamma binding. In contrast, when tyrosine-12 is diiodinated, toxin binding is nearly irreversible at the alpha/delta site but also increases by approximately 500-fold at the alpha/gamma site. The effects of position 12 substitutions are accounted for almost entirely by changes in the rate of toxin dissociation from the high-affinity alpha/delta binding site.

A novel D-leucine-containing Conus peptide: diverse conformational dynamics in the contryphan family.

A Conus peptide family (the contryphans) is noteworthy because of the presence of a post-translationally modified D-amino acid in all members of the family. A new contryphan peptide, Leu-contryphan-P, was isolated from the venom of Conus purpurascens; the sequence of this peptide is: Gly-Cys-Val-D-Leu-Leu-Pro-Trp-Cys-OH. This is the first known occurrence of D-leucine in a Conus peptide. The discovery of Leu-contryphan-P suggests that there may be branches of the contryphan peptide family that diverge much more in sequence than previously anticipated. Several natural contryphans provide dramatic examples of interconversion between multiple conformational states in small constrained peptides. The contryphans that have 4-trans-hydroxyproline and D-tryptophan in positions 3 and 4, respectively, exhibit two peaks under reverse-phase HPLC conditions, indicating interconversion between two discrete conformations. However, [L-Trp4]contryphan-Sm (with L-Trp substituted for D-Trp) exhibits a single, broad peak that elutes later than the natural peptide, suggesting that D-Trp stabilizes a conformation in which hydrophobic residues are buried. Leucontryphan-P which has valine and D-leucine instead of 4-trans-hydroxyproline and D-tryptophan shows only a single peak that elutes much later than the other contryphans.

alpha-conotoxin AuIB selectively blocks alpha3 beta4 nicotinic acetylcholine receptors and nicotine-evoked norepinephrine release.

Neuronal nicotinic acetylcholine receptors (nAChRs) with putative alpha3 beta4-subunits have been implicated in the mediation of signaling in various systems, including ganglionic transmission peripherally and nicotine-evoked neurotransmitter release centrally. However, progress in the characterization of these receptors has been hampered by a lack of alpha3 beta4-selective ligands. In this report, we describe the purification and characterization of an alpha3 beta4 nAChR antagonist, alpha-conotoxin AuIB, from the venom of the "court cone," Conus aulicus. We also describe the total chemical synthesis of this and two related peptides that were also isolated from the venom. alpha-Conotoxin AuIB blocks alpha3 beta4 nAChRs expressed in Xenopus oocytes with an IC50 of 0.75 microM, a kon of 1.4 x 10(6) min-1 M-1, a koff of 0.48 min-1, and a Kd of 0.5 microM. Furthermore, alpha-conotoxin AuIB blocks the alpha3 beta4 receptor with >100-fold higher potency than other receptor subunit combinations, including alpha2 beta2, alpha2 beta4, alpha3 beta2, alpha4 beta2, alpha4 beta4, and alpha1 beta1 gamma delta. Thus, AuIB is a novel, selective probe for alpha3 beta4 nAChRs. AuIB (1-5 microM) blocks 20-35% of the nicotine-stimulated norepinephrine release from rat hippocampal synaptosomes, whereas nicotine-evoked dopamine release from striatal synaptosomes is not affected. Conversely, the alpha3 beta2-specific alpha-conotoxin MII (100 nM) blocks 33% of striatal dopamine release but not hippocampal norepinephrine release. This suggests that in the respective systems, alpha3 beta4-containing nAChRs mediate norepinephrine release, whereas alpha3 beta2-containing receptors mediate dopamine release.

mu-Conotoxin PIIIA, a new peptide for discriminating among tetrodotoxin-sensitive Na channel subtypes.

We report the characterization of a new sodium channel blocker, mu-conotoxin PIIIA(mu-PIIIA). The peptide has been synthesized chemically and its disulfide bridging pattern determined. The structure of the new peptide is: [sequence: see text] where Z = pyroglutamate and O = 4-trans-hydroxyproline. We demonstrate that Arginine-14 (Arg14) is a key residue; substitution by alanine significantly decreases affinity and results in a toxin unable to block channel conductance completely. Thus, like all toxins that block at Site I, mu-PIIIA has a critical guanidinium group. This peptide is of exceptional interest because, unlike the previously characterized mu-conotoxin GIIIA (mu-GIIIA), it irreversibly blocks amphibian muscle Na channels, providing a useful tool for synaptic electrophysiology. Furthermore, the discovery of mu-PIIIA permits the resolution of tetrodotoxin-sensitive sodium channels into three categories: (1) sensitive to mu-PIIIA and mu-conotoxin GIIIA, (2) sensitive to mu-PIIIA but not to mu-GIIIA, and (3) resistant to mu-PIIIA and mu-GIIIA (examples in each category are skeletal muscle, rat brain Type II, and many mammalian CNS subtypes, respectively). Thus, mu-conotoxin PIIIA provides a key for further discriminating pharmacologically among different sodium channel subtypes.

Adult responses to child behavior and attitudes toward fathering: gay and nongay fathers.

This study examines gay and nongay fathers' responses to instruments measuring parenting style and orientation to the fathering role. Fifty-three respondents (24 gay and 29 nongay fathers) completed two surveys, and responses to each were analyzed. Both groups of fathers were found to have a developmental orientation toward their role as fathers, and no discernible parenting style could be found to distinguish one group from the other. Thus, gay and nongay fathers were found to be more similar than different with regard to parenting styles and attitudes toward fathering. This finding supports previous work (Bigner & Jacobsen, 1989a, 1989b) and expands the available knowledge based on the parenting styles of homosexual parents.

The value of children to gay and heterosexual fathers.

Responses of 33 gay fathers were compared with those of 33 heterosexual fathers on the Value of Children scale, an empirical measure of the reasons for wanting to become a parent. Responses of gay fathers did not differ significantly from heterosexual fathers on the majority of the items of the inventory, but differences were found on two subscales, Tradition-Continuity-Security and Social Status. Item analysis of responses shows that gay fathers may have particularly significant reasons motivating them to become parents.

Parenting behaviors of homosexual and heterosexual fathers.

Responses of 33 homosexual (gay) fathers were compared with those of 33 heterosexual (nongay) fathers on the Iowa Parent Behavior Inventory, an empirical measure of dimensions of parenting behavior. Gay fathers did not differ significantly from nongay fathers in their reported degree of involvement nor in intimacy level with children. Gay fathers tended to be more strict, more responsive to children's needs, and to provide reasons for appropriate behavior to children more consistently than nongay fathers. Several explanations are explored for these similarities and differences in parenting styles.

The child's home environment for lesbian vs. heterosexual mothers: a neglected area of research.

Much research on the lesbian experience has focused on assessing differences between lesbian and heterosexual adults. Less effort has been expended in analyzing the home environment of the child in a lesbian household. This study compares samples of lesbian and heterosexual mothers in terms of the home setting provided and the caregiver role vs-à-vis children. Results reveal a less affluent socioeconomic setting for the children of lesbian mothers. A strong child-development orientation was found among lesbian mothers, undermining the stereotype of lesbians as aloof from children.