Detection of integrins in human cataract lens epithelial cells and two mammalian lens epithelial cell lines

AIM

To compare the incidence of various integrin subunits in human cataract anterior lens epithelial cells (A-LEC) and in two mammalian LEC lines.

METHODS

Circular sections of anterior capsules with attached LEC were obtained during cataract surgery. Integrin subunits were immunolocalised in these anterior LEC and in a human and rabbit LEC line, using four monoclonal antibodies specific for subunits alpha2, alpha3, and alpha5, and beta subunit 2.

RESULTS

All of these subunits were found in at least a proportion A-LEC samples as follows: alpha2 71%, alpha3 92%, alpha5 62%, and beta2 24%. The human LEC line was immunoreactive for alpha2 and alpha3 only. The rabbit lens epithelial cell line was immunoreactive for alpha5 but there was no staining for alpha2, alpha3, or beta2.

CONCLUSION

The A-LEC and mammalian LEC lines showed a similarity in their pattern of integrin expression. As these integrins are receptors for extracellular matrix (ECM) components, they are likely to be associated with the attachment and migration of LECs that precedes capsular opacification. Therefore these cell lines may be useful in the elucidation of mechanisms involved the pathogenesis of capsule opacification.

Presynaptic modulation of GABAergic inhibition by GABA(B) receptors in the rat's inferior colliculus

Whole-cell patch clamp recordings were made from neurons in a brain slice preparation of the inferior colliculus in 11-15-day-old rat pups. Synaptic responses were elicited by applying a current pulse to the lateral lemniscus just below the central nucleus of the inferior colliculus. To examine GABAergic inhibition in the inferior colliculus all excitatory postsynaptic potentials and glycinergic inhibitory postsynaptic potentials were blocked by bath application of their respective antagonists and the contribution of GABA(B) receptors was determined for the remaining inhibitory postsynaptic potentials. For most cells the isolated inhibitory postsynaptic potential was completely blocked by the GABA(A) receptor antagonist, bicuculline, but was unaffected by the GABA(B) receptor antagonist, phaclofen. The GABA(B) receptor agonist, baclofen (10-20 microM), decreased the amplitude of the inhibitory postsynaptic potentials. This effect was completely blocked by phaclofen. Baclofen did not increase the cell membrane conductance or alter the rate of firing produced by depolarization of the cell membrane. In contrast, muscimol, a GABA(A) receptor agonist, greatly increased membrane conductance and lowered the firing rate produced by depolarization. Our results indicate that GABAergic inhibition in the auditory midbrain can be reduced by the activation of GABA(B) receptors and suggest that the effects are presynaptic.

Long-term outcome of uncomplicated infantile exotropia

PURPOSE

The term congenital exotropia (XT) is typically reserved for patients presenting in the first year with a large, constant angle, however, no published study provides a rationale for this restrictive definition. In this study, the present classification system for XT was evaluated and differences between infants with constant versus intermittent XT at presentation were characterized.

METHODS

Medical records of all patients diagnosed with XT before 12 months of age between 1980 and 1994 were identified by computer search. Exclusion criteria included previous eye muscle surgery, resolution of the XT by 3 months of age, and concomitant systemic or ocular disease. Patients were separated into intermittent XT and constant XT groups. The clinical characteristics and outcomes of these two groups were compared.

RESULTS

Of 2018 patients examined on our service during the first year of life for all causes, 23 (1.1 %) met the inclusion criteria. Follow-up data of more than 1 year was available for 13 patients, and of these, 46% had constant XT. The 2 groups had similar clinical features at presentation except for a larger initial angle in the constant XT group (P =.02). Average follow-up was 58 months (range: 13-158 months). Twelve patients (92%) required surgery. The reoperation rate was 27%, and 82% had final horizontal deviations of less than 10 PD. The incidence of A/V-patterns (38%), dissociated vertical deviation (46%), and binocularity (70%) was similar between groups.

CONCLUSION

Half of infantile XT patients may present with intermittent XT, with similar clinical outcomes regardless of presentation. Surgical intervention resulted in successful alignment in most cases. More than half the patients developed measurable stereopsis, but none achieved bifixation.

AMPA and NMDA receptors regulate responses of neurons in the rat's inferior colliculus

The contribution of N-methyl-D-aspartate (NMDA) and AMPA receptors to auditory responses in the rat's inferior colliculus was examined by recording single-unit activity before, during, and after local iontophoretic application of receptor-specific antagonists. Tone bursts and sinusoidal amplitude modulated sounds were presented to one ear, and recordings were made from the contralateral central nucleus of inferior colliculus (ICC). The receptor specific antagonists, (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) for NMDA receptors and 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX) for AMPA receptors, were released at the recording site through a multi-barreled pipette. For most neurons, either CPP or NBQX alone resulted in a reversible reduction in the number of action potentials evoked by tonal stimulation. For neurons with an onset response pattern, NBQX either completely eliminated or greatly reduced the number of action potentials. CPP also reduced the number of action potentials but had a less pronounced effect than NBQX. For neurons with a sustained firing pattern, NBQX reduced the total number of action potentials, but had a preferential effect on the early part (first 10-20 ms) of the response. CPP also resulted in a reduction in the total number of action potentials, but had a more pronounced effect on the later part (>20 ms) of the response. These results indicate that both AMPA and NMDA receptors contribute to sound evoked excitatory responses in the ICC. They have a selective influence on early and late components of tone-evoked responses. Both receptor types are involved in generating excitatory responses across a wide range of sound pressure levels as indicated by rate level functions obtained before and during drug application. In addition, both CPP and NBQX reduced responses to sinusoidal amplitude modulated sounds. The synchrony of firing to the modulation envelope as measured by vector strength at different rates of modulation was not greatly affected by either CPP or NBQX in spite of the decrease in firing rate.

Children's adjustment in conflicted marriage and divorce: a decade review of research

OBJECTIVES

To review important research of the past decade in divorce, marital conflict, and children's adjustment and to describe newer divorce interventions.

METHOD

Key empirical studies from 1990 to 1999 were surveyed regarding the impact of marital conflict, parental violence, and divorce on the psychological adjustment of children, adolescents, and young adults.

RESULTS

Recent studies investigating the impact of divorce on children have found that many of the psychological symptoms seen in children of divorce can be accounted for in the years before divorce. The past decade also has seen a large increase in studies assessing complex variables within the marriage which profoundly affect child and adolescent adjustment, including marital conflict and violence and related parenting behaviors. This newer literature provides provocative and helpful information for forensic and clinical psychiatrists in their work with both married and divorcing families.

CONCLUSIONS

While children of divorced parents, as a group, have more adjustment problems than do children of never-divorced parents, the view that divorce per se is the major cause of these symptoms must be reconsidered in light of newer research documenting the negative effects of troubled marriages on children.

NMDA and AMPA receptors in the dorsal nucleus of the lateral lemniscus shape binaural responses in rat inferior colliculus

Binaural responses of single neurons in the rat's central nucleus of the inferior colliculus (ICC) were recorded before and after local injection of excitatory amino acid receptor antagonists (either 1,2, 3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium [NBQX], (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid [CPP], 6-cyano-7-nitroquinoxaline-2,3-dione [CNQX], or (+/-)-2amino-5-phosphonovaleric acid [APV]) into the dorsal nucleus of the lateral lemniscus (DNLL). Responses were evoked by clicks delivered separately to the two ears at interaural time delays between -1.0 and +30 ms (positive values referring to ipsilateral leading contralateral click pairs). The neurons in our sample were excited by contralateral stimulation and inhibited by ipsilateral stimulation, and the probability of action potentials was reduced as the ipsilateral stimulus was advanced. Binaural inhibition resulted in response suppression that lasted up to 30 ms. Injection of excitatory amino acid antagonists into the DNLL contralateral to the recording site reduced the strength of binaural inhibition in the ICC. The alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist NBQX preferentially affected responses at small interaural time intervals (0-1.0 ms), whereas the N-methyl-D-aspartate (NMDA) antagonist CPP preferentially affected responses at longer intervals (1-30 ms). Both CNQX and APV produced a release from binaural inhibition, but neither drug was selective for specific intervals. The data support the idea that binaural inhibition in the rat ICC is influenced by both AMPA and NMDA receptor-mediated excitatory events in the contralateral DNLL. The results suggest that the AMPA receptors contribute selectively to the initial component of binaural inhibition and the NMDA receptors to a longer lasting component.

The commissure of probst as a source of GABAergic inhibition

Whole-cell patch-clamp recordings were made from neurons in the rat's dorsal nucleus of the lateral lemniscus (DNLL) in a brain slice preparation. Planes of section were chosen to preserve the integrity of fibers in the commissure of Probst (CP) and postsynaptic responses were evoked by electrical stimulation along its length. Results showed that the crossed projection to the DNLL through the CP is mainly, if not exclusively, inhibitory in the rat. Inhibitory postsynaptic responses (IPSPs) evoked by stimulation of the CP were blocked by the gamma-aminobutyric acid (GABA)(A) receptor antagonist bicuculline, but were unaffected by the glycine receptor antagonist strychnine, supporting the conclusion that the crossed inhibitory projection to DNLL from the contralateral DNLL is GABAergic. Stimulation of the CP close to the DNLL frequently evoked excitatory postsynaptic responses as well as IPSPs, but stimulation near the midline evoked IPSPs only. Thus, the excitatory responses probably originated from a pathway other than the projection to the DNLL from the contralateral DNLL through the CP.

Neural architecture of the rat medial geniculate body

The rat medial geniculate body was subdivided using Nissl preparations to establish nuclear boundaries, with Golgi-Cox impregnations to identify projection and local circuit neurons, and in fiber stained material to delineate the fiber tracts and their distribution. Three divisions were recognized (ventral, dorsal and medial): the first two had subdivisions. The ventral division had lateral and medial parts. The main cell type had bushy tufted dendrites which, with the afferent axons, formed fibrodendritic laminae oriented from dorso-lateral to ventro-medial; such laminae were not as regular medially, in the ovoid nucleus. The dorsal division contained several nuclei (dorsal superficial, dorsal, deep dorsal, suprageniculate, and ventrolateral) and neurons with radiating or bushy dendrites; the nuclear subdivisions differed in the concentration of one cell type or another, and in packing density. A laminar organization was present only in the dorsal superficial nucleus. Medial division neurons were heterogeneous in size and shape, ranging from tiny cells to magnocellular neurons; the various cell types intermingled. so that no further subdivision could be made. This parcellation scheme was consistent with, and supported by, the findings from plastic embedded or fiber stained material. There were very few small neurons with locally ramifying axons and which could perform an intrinsic role like that of Golgi type II cells. Their rarity was consistent with the small number of such profiles in plastic embedded or Nissl material and the few GABAergic medial geniculate body neurons seen in prior immunocytochemical work. While similar neuronal types and nuclear subdivisions are recognized in the rat and cat, there may be major interspecific differences with regard to interneuronal organization in the auditory thalamus whose functional correlates are unknown.

Origins of medial geniculate body projections to physiologically defined zones of rat primary auditory cortex

Medial geniculate body neurons projecting to physiologically identified subregions of rat primary auditory cortex (area 41, Te1) were labeled with horseradish peroxidase in adult rats. The goals were to determine the type(s) of projection neuron and the spatial arrangement of these cells with respect to thalamic subdivisions. Maps of best frequency were made with single neuron or unit cluster extracellular recording at depths of 500-800 microm, which correspond to layers III-IV in Nissl preparations. Tracer injections were made in different cortical isofrequency regions (2, 11, 22, or 38 kHz, respectively). Labeled neurons were plotted on representative sections upon which the architectonic subdivisions were drawn independently. Most of the cells of origin lay in the ventral division in every experiment. Injections at low frequencies labeled bands of neurons laterally in the ventral division; progressively more rostral deposits at higher frequencies labeled bands or clusters more medially in the ventral division, and through most of its caudo-rostral extent. Medial division labeling was variable. Labeled cells were always in the lateral half of the nucleus and were often scattered. There were few labeled cells in the dorsal division. Seven types of thalamocortical neuron were identified: ventral division cells had a tufted branching pattern, while medial division neurons have heterogeneous shapes and sizes and were larger. Dorsal division neurons had a radiate branching pattern. The size range of labeled neurons spanned that of Nissl stained neuronal somata. Area 41 may receive two types of thalamic projection: ventral division input is strongly convergent, highly topographic, spatially focal, and restricted to one type of neuron only, while the medial division projection is more divergent, coarsely topographical, involves multiple cortical areas, and has several varieties of projection neuron. Despite species differences in local circuitry, many facets of thalamocortical organization are conserved in phylogeny.

Contribution of the commissure of Probst to binaural evoked responses in the rat's inferior colliculus: interaural time differences

Binaural evoked responses were recorded with glass micropipettes from the central nucleus of the rat's inferior colliculus (ICC) before and after transection of the commissure of Probst (CP) with a microsurgical knife. The peak-to-peak amplitude of the averaged evoked response was measured for binaural clicks with interaural time differences (ITDs) between -1.0 and +30.0 ms (positive values reflecting ipsilateral-leading-contralateral click pairs). Before transection, the amplitude of the evoked response decreased as the ITD was shifted in favor of larger ipsilateral lead times. After transection of the CP, acoustic stimulation of the ipsilateral ear was much less effective in reducing evoked response amplitude. Responses to both short (+/-1.0 ms) and long (1.0-30.0 ms) ITD intervals were affected. After recordings were made, both anterograde and retrograde tract tracing methods were used to verify that the CP was completely transected and that all crossed projections from the dorsal nucleus of the lateral lemniscus (DNLL) to ICC were destroyed. The surgery completely eliminated the retrograde transport of fluorogold from the ICC to the opposite DNLL and blocked the anterograde transport of biotinylated dextran to contralateral DNLL and ICC. The physiological consequences of CP transection are attributed to the complete destruction of decussating, inhibitory (GABAergic) efferent projections from the DNLL.

Kainic acid lesions of the superior olivary complex: effects on sound localization by the albino rat

The ability of rats to localize sounds in space was determined before and after kainic acid lesions of the superior olivary complex (SOC). Animals were tested with a 45-ms noise burst delivered from loudspeakers on the right or left of midline. Anatomical data showed that the lesions destroyed neurons in SOC while preserving fibers of passage in the trapezoid body and other decussating pathways of the auditory brainstem. Animals with either unilateral or bilateral SOC lesions were impaired in their ability to localize a single noise burst postoperatively. Deficits were also found after unilateral lesions restricted primarily to the lateral superior olive. SOC lesions resulted in an elevation in minimum audible angles for sound localization.

Monaural and binaural response properties of single neurons in the rat's dorsal nucleus of the lateral lemniscus

Extracellular recordings were made with microelectrodes from single neurons in the rat's dorsal nucleus of the lateral lemniscus (DNLL) and response characteristics were determined for monaural and binaural acoustic stimulation. The vast majority of DNLL neurons were narrowly tuned to sound frequency and their temporal responses to contralateral tone pulses fell into one of three broad categories: onset (57%), sustained (21%) or onset-pause-sustained (22%). Most DNLL neurons fired multiple action potentials to a single click delivered to the contralateral ear. The majority (77%) of DNLL neurons showed a monotonic increase in the number of spikes elicited by contralateral tone pulses of increasing sound pressure level; the remaining cells were weakly non-monotonic. No obvious tonotopic pattern was found in the distribution of characteristic frequency of neurons in DNLL. Most DNLL neurons exhibited either excitatory/inhibitory (74%) or excitatory/excitatory (9%) binaural response patterns. The remaining cells (17%) were monaural and driven exclusively by stimulation of the contralateral ear. The binaural neurons in DNLL were sensitive to both interaural intensity and interaural time differences as determined by presentation of dichotic tone bursts and clicks respectively. The responses of DNLL neurons could be distinguished on the basis of monaural and binaural response characteristics from those in surrounding areas including the sagulum, paralemniscal zone and the intermediate nucleus of the lateral lemniscus.

Kainic acid lesions of the superior olivary complex: effects on sound localization by the albino rat

The ability of rats to localize sounds in space was determined before and after kainic acid lesions of the superior olivary complex (SOC). Animals were tested with a 45-ms noise burst delivered from loudspeakers on the right or left of midline. Anatomical data showed that the lesions destroyed neurons in SOC while preserving fibers of passage in the trapezoid body and other decussating pathways of the auditory brainstem. Animals with either unilateral or bilateral SOC lesions were impaired in their ability to localize a single noise burst postoperatively. Deficits were also found after unilateral lesions restricted primarily to the lateral superior olive. SOC lesions resulted in an elevation in minimum audible angles for sound localization.

Marital conflict, divorce, and children's adjustment

This article summarizes current research on children's adjustment after separation and divorce, and then focuses on the contributions of marital conflict, marital violence, and hostile family environments to children's adjustment during marriage and after divorce. Children living in marriages with frequent and intense conflict are significantly more likely to have substantial adjustment problems before parental divorce and compromised parent-child relationships. These findings suggest that the deleterious effects of divorce per se have been overstated, with insufficient attention paid in the clinical and research literature to the damaging effects of highly troubled marriages on children's adjustment.

GABAergic projections from the lateral lemniscus to the inferior colliculus of the rat

The objective of the present study was to provide direct evidence regarding GABAergic projections from the nuclei of the lateral lemniscus to the central nucleus of the inferior colliculus (ICC), and from the ICC to the opposite ICC. Projections of GABAergic neurons in the rat were investigated by a combination of fluorogold (FG) retrograde tracing and GABA immunocytochemistry. FG was first injected into a frequency-defined region (11-13 kHz) in the center of the ICC, and 1-2 weeks was allowed for retrograde transport. Vibratome sections were then cut through the brainstem and stained with GABA antibody. Double-labeling was taken as evidence of GABAergic neurons projecting to the ICC. The results from FG retrograde labeling alone showed that neurons in the dorsal nucleus of the lateral lemniscus (DNLL) bilaterally, in the intermediate and ventral nucleus of the lateral lemniscus (INLL and VNLL) ipsilaterally, and in the ICC contralaterally project to the ICC. GABA immunostaining alone showed substantial numbers of GABA positive neurons in the nuclei of the lateral lemniscus and the inferior colliculus. FG and GABA double-labeled neurons were present in all nuclei of the lateral lemniscus that project to the ICC. The greatest concentration of double-labeled neurons was found bilaterally in the DNLL, suggesting a prominent GABAergic projection from the DNLL to the ICC. The presence of many double-labeled neurons in the ipsilateral INLL and VNLL suggests that there are also GABAergic inputs from the INLL and VNLL to the ICC. No double-labeled neurons were found in the contralateral ICC, which suggests the possibility of a prominent non-GABAergic projection.

Projections from the superior olive and lateral lemniscus to tonotopic regions of the rat's inferior colliculus

The projections to physiologically defined tonotopic regions of the central nucleus of the inferior colliculus (ICC) from the adult rat's superior olivary complex (SOC) and lateral lemniscus were investigated using retrograde tract tracing methods. Iontophoretic injections of the retrograde tracers, Fluoro-Gold (FG) or horseradish peroxidase (HRP), were made into the ICC through a glass micropipette, which also served as a recording electrode to determine the frequency response at the injection site. Injections were made into frequency-specific regions based on the best responses of neurons to contralaterally presented tones between 2 25 kHz. In the dorsal nucleus of the lateral lemniscus (DNLL) neurons were labeled both ipsilaterally and contralaterally to the injection site with a larger proportion projecting to the contralateral side. The distribution of labeled cells was concentric, with high frequencies represented along the outer margin and low frequencies represented centrally within DNLL. The lateral superior olive (LSO) was labeled bilaterally, with high frequencies represented medially and low frequencies laterally along the nuclear axis. The projection from the medial superior olive (MSO) was ipsilateral, with high frequencies represented ventrally and low frequencies dorsally. The projection from the superior paraolivary nucleus (SPN) was also largely ipsilateral, with high frequencies represented medially and low frequencies laterally. The intermediate and ventral nuclei of the lateral lemniscus (INLL and VNLL) were also labeled ipsilaterally and exhibited a distribution of tracer that depended on the frequency of the injection site: the low frequency projection was banded but the high frequency projection was more evenly distributed.

Synaptic excitation in the dorsal nucleus of the lateral lemniscus: whole-cell patch-clamp recordings from rat brain slice

The synaptic events underlying the excitation of neurons in the rat's dorsal nucleus of the lateral lemniscus were studied by whole-cell patch-clamp recordings in a brain slice preparation of the auditory midbrain. Both current-clamp and voltage-clamp data were obtained with the brain slice submerged in artificial cerebrospinal fluid. The rats were between 21 and 35 days of age at the time the recordings were made. Synaptic responses were evoked by a bipolar stimulating electrode placed on the lateral lemniscus just ventral to the dorsal nucleus. To eliminate glycinergic inhibitory responses, all physiological data were gathered with 0.5 microM strychnine added to the saline bath. Under current-clamp conditions, excitatory postsynaptic potentials could be subdivided into early and late components. The early component produced a single, highly reliable, short-latency spike and the later component produced a more variable, long-latency spike or train of spikes. The non-N-methyl-D-aspartate antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, completely blocked the early excitatory postsynaptic potential and its associated action potential. The N-methyl-D-aspartate antagonist, D,L-2-amino-5-phosphonovaleric acid, blocked the later excitatory postsynaptic potential and its action potentials. Typically, both early and late excitatory postsynaptic potentials could be recorded from the same cell, but the early excitatory postsynaptic potential was evoked at lower stimulus levels and had a larger amplitude than the later excitatory postsynaptic potential. Under voltage-clamp conditions, dorsal nucleus of the lateral lemniscus neurons responded to stimulation of the lateral lemniscus with excitatory postsynaptic currents. Outward excitatory postsynaptic currents were recorded with holding potentials that depolarized the cell membrane and inward currents were seen when the cell was hyperpolarized. The current-voltage (I-V) relation of the early peak portion of the excitatory postsynaptic current was nearly linear, whereas the I-V relation of the later excitatory postsynaptic current (12 ms after the peak) was non-linear over the range between -50 and - 100 mV. The outward excitatory postsynaptic current consisted of an early current that was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dione and a later current that was blocked by D,L-2-amino-5-phosphonovaleric acid. In artificial cerebrospinal fluid with normal concentrations of Mg2+, the inward excitatory postsynaptic current was blocked by 6-cyano-7-nitroquinoxaline-2,3-dione, but was not affected by D,L-2-amino-5-phosphonovaleric acid. In Mg2+-free artificial cerebrospinal fluid. however, the early component of the inward excitatory postsynaptic current was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dione and a later component was blocked by D,L-2-amino-5-phosphonovaleric acid. The results indicate that both N-methyl-D-aspartate and non-N-methyl-D-aspartate receptor-mediated synaptic responses are present in dorsal nucleus of the lateral lemniscus neurons of rats at 21-35 days of age. The N-methyl-D-aspartate component had a longer time-course and a higher threshold than the non-N-methyl-D-aspartate component, and was subject to a voltage-dependent Mg2+ block when the cell's membrane was hyperpolarized. The long-duration N-methyl-D-aspartate component is probably responsible for the prolonged inhibitory effect of dorsal nucleus of the lateral lemniscus neurons on physiological responses in the rat's inferior colliculus.

Vagal preganglionic projections to the enteric nervous system characterized with Phaseolus vulgaris-leucoagglutinin

The patterns and extent of vagal preganglionic divergence and convergence within the gastrointestinal tract of the rat were characterized with the anterograde tracer Phaseolus vulgaris-leucoagglutinin (PHA-L). Three weeks after tracer was iontophoretically injected into two to four sites within the dorsal motor nucleus of the vagus, wholemounts of perfused gut organs (stomach, duodenum, cecum) were prepared, counterstained with Cuprolinic blue, and processed for PHA-L using the avidin biotin complex with diaminobenzidine. Controls included animals injected with PHA-L after intracranial deafferentations. Well-positioned injections labeled an extremely dense and intricate network of varicose efferent axons throughout the gastric myenteric plexus (including that of the fundus). Individual fibers collateralized extensively, forming a variety of pericellular arborizations and terminal complexes made up of both en passant and end swellings. Single axons frequently innervated subsets of neurons within ganglia. Most enteric neurons were contacted by varicosities of more than one vagal fiber. The patterns of vagal preganglionic fibers in the duodenal and cecal myenteric plexuses resembled the organization in the stomach in many aspects, but the projections in each organ had distinctive characteristics, and label was less dense in the intestines than in the stomach. Vagal preganglionic fibers directly innervated submucosal ganglia, although sparsely. Brainstem injections of PHA-L retrogradely labeled a few myenteric neurons in the corpus, fundus, and duodenum: These "gastrobulbar" and "duodenobulbar" neurons received reciprocal vagal preganglionic innervation. Finally, the PHA-L that spread to the nucleus of the solitary tract occasionally produced transganglionic labeling of afferent intramuscular arrays (gastric fundus). The results of this paper provide strong evidence that the traditional "command neuron" or "mother cell" hypotheses of vagal-enteric organization should be abandoned for an integrative neural network model.

Sound localization after kainic acid lesions of the dorsal nucleus of the lateral lemniscus in the albino rat

The ability of rats to localize sounds in space was determined before and after kainic acid lesions of the dorsal nucleus of the lateral lemniscus (DNLL). The rats were trained to approach a 45-ms noise burst delivered from loudspeakers on the right or left of midline. Lesions were made by local injection of kainic acid into the DNLL. Rats with unilateral lesions of DNLL were impaired in their postoperative ability to localize a single noise burst. Rats with bilateral lesions also had deficits in postoperative performance, but the severity of the impairment was not substantially greater than that expected from a unilateral lesion. The mean pre- and postoperative minimum audible angles were 14.8 degrees and 40.4 degrees for rats with complete unilateral lesions and 13.5 degrees and 36.0 degrees for rats with bilateral lesions.

Two sources of inhibition affecting binaural evoked responses in the rat's inferior colliculus: the dorsal nucleus of the lateral lemniscus and the superior olivary complex

The present study was undertaken to determine the influence of two extrinsic sources of inhibition on auditory binaural evoked responses recorded from the rat's inferior colliculus. The first source, the dorsal nucleus of the lateral lemniscus (DNLL), is predominantly GABAergic and has both ipsi- and contralateral projections to the central nucleus of the inferior colliculus (ICC). The second, the superior olivary complex (SOC), has a large glycinergic projection from the lateral superior olive (LSO) to the ipsilateral ICC. Thus, both structures are candidates for imposing an inhibitory effect on responses in the ICC. Neural activity was experimentally blocked by local injection of the excitatory amino acids antagonist, kynurenic acid (KYNA), into either DNLL or SOC. Binaural evoked responses were recorded from the ICC as the intensity of the sound in the ipsilateral ear was increased. Interaural intensity difference functions based on the amplitude of the evoked responses were generated before and after the KYNA injection. An injection into the contralateral DNLL greatly reduced the response suppression produced by stimulation of the ipsilateral ear. Injection into the ipsilateral DNLL, however, had no effect. Injection into the ipsilateral SOC reduced the amount of binaural suppression but the effect was apparent only in cases with surgical transection of the contralateral lateral lemniscus at a level below the DNLL. These data support the conclusion that binaural responses in the rat's ICC are shaped by inhibitory projections from both contralateral DNLL and ipsilateral SOC.

Sound localization after kainic acid lesions of the dorsal nucleus of the lateral lemniscus in the albino rat

The ability of rats to localize sounds in space was determined before and after kainic acid lesions of the dorsal nucleus of the lateral lemniscus (DNLL). The rats were trained to approach a 45-ms noise burst delivered from loudspeakers on the right or left of midline. Lesions were made by local injection of kainic acid into the DNLL. Rats with unilateral lesions of DNLL were impaired in their postoperative ability to localize a single noise burst. Rats with bilateral lesions also had deficits in postoperative performance, but the severity of the impairment was not substantially greater than that expected from a unilateral lesion. The mean pre- and postoperative minimum audible angles were 14.8 degrees and 40.4 degrees for rats with complete unilateral lesions and 13.5 degrees and 36.0 degrees for rats with bilateral lesions.

Contribution of the dorsal nucleus of the lateral lemniscus to binaural responses in the inferior colliculus of the rat: interaural time delays

The contribution of the dorsal nucleus of the lateral lemniscus (DNLL) to binaural responses in the inferior colliculus of the rat was determined for a wide range of interaural time differences (ITDs). Single-unit action potentials were recorded from the inferior colliculus before and after local injection of the excitatory amino acid antagonist kynurenic acid into the DNLL. Binaural properties were determined by manipulating the time difference between paired clicks delivered to the ears ipsilateral and contralateral to the recording site. The probability of an action potential decreased as contralateral stimulation was delayed, relative to ipsilateral stimulation. These data generated a sigmoidal ITD curve for delays between -1.0 and + 1.0 msec. By extending the time intervals beyond 1 msec, it was possible to determine the trailing edge of the inhibition produced by ipsilateral stimulation. The duration of the inhibitory effect varied from cell to cell but lasted as long as 20 msec in some cases. Injection of kynurenic acid into the DNLL contralateral to the recording site reduced the extent of both short (0-1 msec) and long-lasting (1-20 msec) inhibition in the inferior colliculus. No effect was seen after injections ipsilateral to the recording site. The data demonstrate that the DNLL plays an important role in shaping ITD responses in the inferior colliculus and contributes to both the short and long-lasting inhibition produced by stimulation of the ipsilateral ear.

Sound localization after transection of the commissure of Probst in the albino rat

1. The ability of rats to localize sounds in space was determined before and after cutting of the commissure of Probst. The commissure of Probst was transected at its midline decussation with a microknife inserted into the brain according to stereotaxic coordinates. Six animals were tested after extensive lesions that destroyed all of the commissure of Probst fibers. An additional animal was tested after a smaller lesion that destroyed most of the commissure of Probst but left some fibers intact. Three control animals were tested before and after surgical intervention that did not involve the commissure of Probst. 2. The animals were tested in a semicircular apparatus with loudspeakers located on the right or left of midline. They were trained to make a response toward the left or right in the direction of the active loudspeaker. Correct reponses were rewarded by delivery of a small quantity of water from spouts located at +30 and -30 degrees azimuth. Tests of sound localization were conducted with a single broadband noise burst, 45 ms in duration, presented at the beginning of each trial. The position of the active loudspeakers was varied from trial to trial and performance at different speaker angles was calculated to determine psychometric curves. Minimum audible angles were estimated by interpolation from a performance level of 75% correct. 3. After postoperative testing was completed, the effectiveness of the lesions was confirmed by cell counts to determine the extent of retrograde degeneration in the dorsal nucleus of the lateral lemniscus (DNLL). These data showed that most of the contralaterally projecting neurons in DNLL underwent retrograde degeneration and the number of neurons was reduced by 60-65%. Ninety to 95% of the contralaterally projecting neurons in the DNLL disappeared within 7 wk after transection of the commissure of Probst. 4. The condition of damaged commissural fibers was further confirmed by tract tracing methods. A unilateral Fluoro-Gold injection was made into the inferior colliculus and the auditory brain stem was examined for retrograde label. No labeled neurons were seen in the contralateral DNLL in cases with complete transection of the commissure of Probst. In addition, the distribution of Fluoro-Gold labeling in other brain stem auditory structures was similar to that seen in normal animals. This result confirmed that the transection of the commissure of Probst was successful and that projections to other auditory structures remained intact. 5. Transection of the commissure of Probst produced marked deficits in midline sound localization. Although sound localization was still possible, there was a degradation in the ability of rats to localize sounds in the horizontal plane. The mean minimum audible angle was elevated 22.1 degrees after destruction of the commissure of Probst compared with a shift of only 2.0 degrees in control animals.

Potassium currents and membrane excitability of neurons in the rat's dorsal nucleus of the lateral lemniscus

1. The contribution of voltage-activated outward potassium currents to membrane excitability of neurons in the rat's dorsal nucleus of the lateral lemniscus (DNLL) was studied in a brain slice preparation using whole cell patch-clamp and intracellular recordings. Voltage-clamp methods and pharmacological manipulations were used to examine the currents regulating membrane dynamics in DNLL. 2. A delayed sustained outward current was evoked by applying depolarizing voltage steps across the cell membrane from a holding potential of -50 mV. An additional transient outward current was evoked when the depolarizing steps were preceded by a hyperpolarizing prepulse of -110 or -120 mV. 3. The transient outward current peaked within 6.8 ms of the onset of a depolarizing pulse. It decayed with a time constant of 12.3 ms for a 60-mV depolarizing voltage shift. Half-inactivation of this current occurred at -81.3 mV. The time constant for removal of the inactivation was 17.4 ms. The transient current had a high sensitivity to 4-aminopyridine (4-AP). 4. The sustained current was activated more slowly and was more sensitive to tetraethylammonium (TEA) than the transient current. The sustained current had both Ca2+-dependent and Ca2+-independent components. The Ca2+-dependent portion emerged at potentials of about -35 mV and was activated fully at +10 mV. The Ca2+-independent component was activated at potentials more positive than -40 mV and increased in magnitude with further depolarization. Inactivation of the Ca2+-independent component was voltage dependent. Also, TEA suppressed the Ca2+-independent compound. 5. The transient current in DNLL neurons closely resembled the A current (IA) described for hippocampal and other neurons in both kinetics and pharmacology. The Ca2+-independent component of the sustained current resembled the K current (IK) described for other neurons in both its properties of activation and inactivation and its pharmacology. 6. The outward current of some DNLL neurons was found to contain a dendrotoxin-sensitive component. This component reached its peak at 6.8 ms and had voltage-sensitive time constants of decay of 25.5 and 8.5 ms with voltage steps of 40 and 60 mV, respectively. 7. Application of 4-AP and TEA markedly prolonged the spike width, abolished the fast component of the after hyperpolarization and depolarized the cell membrane. Also, the number of action potentials produced by positive current injection increased under the influence of 4-AP and TEA. Membrane excitability and spike repolarization were dependent on both 4-AP-sensitive transient and TEA-sensitive sustained currents. 8. Neurons in DNLL typically exhibit a steady discharge of action potentials in response to sustained membrane depolarization. The rate and temporal pattern of production of action potentials in these cells are determined by the combination of transient and sustained potassium channels.

Effects of bilateral auditory cortical lesions on gap-detection thresholds in the ferret (Mustela putorius)

Ferrets were tested for their ability to detect temporal gaps in noise before and after bilateral lesions of the primary auditory cortex. Thresholds for gap detection were determined first for normal animals with band-pass noises at various center frequencies (0.5 to 32 kHz) and at 8 kHz with various sound pressure levels (-10-70 dB). Gap-detection ability improved steadily as sound pressure increased up to 70 dB. No systematic relation was found between threshold and center frequency. To determine the effects of brain damage, ferrets were tested with 8-kHz band-pass noise at 70 dBSPL. After bilateral lesions of auditory cortex, ferrets were still capable of detecting gaps, but the mean threshold was elevated from 10.1 to 20.1 ms. The data demonstrate that auditory cortex is important for perceptual tasks requiring fine temporal resolution.

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. III. synaptic pharmacology

1. The synaptic pharmacology of the dorsal nucleus of the lateral lemniscus (DNLL) of the rat was investigated in a brain slice preparation of the auditory midbrain. The brain slice was cut in the coronal plane and placed in a small recording chamber where warm, oxygenated saline was continuously perfused over and underneath the tissue. Intracellular recordings were made with glass microelectrodes filled with 4 M potassium acetate. Synaptic potentials were elicited by electrical stimulation of the lateral lemniscus or commissure of Probst and pharmacological effects were tested by bath application of amino acid agonists and antagonists. 2. The cells in DNLL were challenged with the excitatory amino acid (EAA) agonists, alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA), N-methyl-D-aspartic acid (NMDA) in 0 Mg2+, and L-glutamate. Each of these caused a depolarization of the cell membrane, a reduction in cell membrane resistance, and the onset of spontaneous firing. 3. Short-latency excitatory postsynaptic potentials (EPSPs) were evoked by stimulation of the lateral lemniscus in 77% of the neurons tested. The mean latency to initial depolarization was 0.9 ms. A single spike with relatively constant latency (mean 1.5 ms) was typically elicited when the strength of lemniscal stimulation was increased. A longer-latency EPSP (mean 2.9 ms) was seen in 34% of the neurons tested either with the slice in normal saline or after pharmacological block of the earlier, short-latency EPSP. The long-latency EPSP was followed by a single spike of multiple spikes with highly variable latencies (range 3.2-24 ms). In 28% of the neurons tested, both early and late EPSPs were observed in response to stimulation of a single location on the lateral lemniscus. 4. Stimulation of the commissure of Probst elicited short-latency EPSPs (mean 0.9 ms) in 37% of the neurons tested. Longer-latency EPSPs (mean 3.0 ms) were found in only 3% of the neurons in response to commissural stimulation. 5. The nonspecific EAA antagonist kynurenic acid blocked both short-and long-latency EPSPs evoked by either lemniscal or commissural stimulation. The non-NMDA antagonist 6-cyano-7-nitro-quinoxaline-2,3-dione (CNQX), at very low concentrations, blocked the short-latency EPSPs but had no effect on the longer-latency EPSPs. The short-latency EPSPs were unaffected by the NMDA antagonist D,L-2-amino-5-phosphonovaleric acid (APV). In contrast, the longer-latency EPSPs were blocked by APV, but never by CNQX. 6. DNLL neurons were affected by the inhibitory amino acid agonists gamma-aminobutyric acid (GABA) and glycine. The membrane resistance of the neurons was decreased by GABA and glycine in a solution of either normal or calcium-free saline in a concentration-dependent manner. 7. Inhibitory postsynaptic potentials (IPSPs) were elicited by stimulation of the lateral lemniscus in 53% of the neurons and the commissure of the Probst in 18% of the neurons tested. The mean latencies were 1.0 and 0.9 ms, respectively. The reversal potentials of the IPSPs were around -70 mV. 8. The IPSPs evoked by stimulation of the lateral lemniscus were blocked by the glycine receptor antagonist strychnine, but not by the GABA receptor antagonist bicuculline, whereas the IPSPs elicited by stimulation of the commissure of Probst were blocked by bicuculline but not strychnine.

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. II. Physiological properties of biocytin-labeled neurons

1. We made intracellular recordings from neurons in rat dorsal nucleus of the lateral lemniscus (DNLL), determined intrinsic and synaptic physiological properties, and labeled the cells by intracellular injection of biocytin. Biocytin-labeled neurons were reconstructed and classified according to their somatic and dendritic morphology. 2. We identified a diversity of morphological cell types in DNLL. Five main groups of neurons were recognized: multipolar; elongate I, II, and III; and round. The multipolar cells were characterized by several large dendrites with multiple branches that spread over large areas within the DNLL. The dendrites radiated equally in all directions. 3. Elongate cells were characterized by extended cell bodies with polar dendrites. In the case of elongate I and II cells, the dendrites were preferentially oriented in the horizontal plane and the dendritic branches extended across most of the cytoarchitectonic breadth of DNLL from the medial to lateral borders. The classification of elongate II was reserved for a single neuron with profuse dendritic branching that fanned out dorsoventrally along the margins of DNLL. This neuron was unique in our sample and was distinguished from the more common elongate I cells, which had less profuse dorsoventral dendritic branching. Elongate III cells had extended cell bodies, but their dendrites did not extend across the DNLL and showed no preferential orientation. 4. Round neurons had relatively small, round cell bodies and radial dendrites that extended over large areas within DNLL. These cells were quite common in our sample and are almost certainly not the same as the infrequently encountered small round cells found in Nissl-stained sections. Some biocytin-labeled neurons were difficult to classify as either multipolar, elongate I, II, or III, or round. These neurons had properties that most closely resembled elongate III cells, but they were treated separately here to minimize heterogeneity within morphological categories. 5. The intrinsic physiological properties measured in this study were uncorrelated with the morphological class of DNLL neurons. All DNLL neurons had similar current-voltage curves regardless of their anatomic category. Intracellular injection of positive current produced a sustained series of action potentials, the number of which was related to the magnitude of current injection. The interspike intervals were regular, although some cells had a tendency toward an increase or decrease in the length of the interval with prolonged current injection. The interspike intervals were regular, although some cells had a tendency toward an increase or decrease in the length of the interval with prolonged current injection. Injection of negative current produced a hyperpolarization that was proportional to the current strength.(ABSTRACT TRUNCATED AT 400 WORDS)

In vitro brain slice studies of the rat's dorsal nucleus of the lateral lemniscus. I. Membrane and synaptic response properties

1. We examined the physiological properties of neurons in the dorsal nucleus of the lateral lemniscus (DNLL) of the rat in a 400-microns tissue slice taken in the frontal plane through the auditory midbrain. The brain slice was placed in a small chamber and was perfused fully submerged in a warm, continuously circulating oxygenated saline solution. We made intracellular recordings with glass pipettes filled with 4 M potassium acetate. Synaptic potentials were evoked by electrical stimulation of either the lateral lemniscus or the commissure of Probst. 2. We tested the membrane characteristics of DNLL neurons by recording the electrical potentials produced by intracellular injection of positive or negative current. Typically, DNLL neurons had nearly linear current-voltage curves and responded to depolarizing currents with a sustained train of action potentials. Injection of intense or prolonged depolarizing currents frequently resulted in a pronounced afterhyperpolarization of the cell membrane. Intense hyperpolarizing currents were often followed by a large rebound depolarization. 3. The action potentials of most DNLL neurons were characterized by a double undershoot, i.e., the initial hyperpolarization after a spike was followed by a second, longer-latency hyperpolarization. Seventy-nine percent of the cells recorded had this type of double undershoot. The remaining cells had a single undershoot in which the postspike hyperpolarization was followed by a steady return to resting potential without any indication of a second phase of hyperpolarization. 4. Electrical stimulation of the lateral lemniscus evoked both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in DNLL. The EPSPs were evoked alone without any evidence of an IPSP in 67% of neurons and IPSPs were evoked alone in 6% of the neurons from which recordings were made. In 27% of the recordings both EPSPs and IPSPs were elicited in the same neuron by stimulation of a single location on the lateral lemniscus. 5. The combined EPSPs and IPSPs produced by lemniscal stimulation could often be dissociated by their different thresholds and/or different response latencies. For 35% of the neurons in which both an EPSP and IPSP were present, the IPSP had a lower threshold; for 23% of the cells, the EPSP had a lower threshold. For the remaining cells the thresholds for producing an EPSP and IPSP were the same. 6. DNLL neurons were capable of responding with great fidelity to a single pulse of stimulation delivered to the lateral lemniscus, i.e., an action potential was evoked after every stimulus.(ABSTRACT TRUNCATED AT 400 WORDS)

Inhibition in the superior olivary complex: pharmacological evidence from mouse brain slice

1. The effects of gamma-aminobutyric acid (GABA) and glycine and their respective antagonists were determined for neurons in the mouse superior olivary complex. Brain slices (400 microns) were cut in the frontal plane and maintained in an oxygenated saline solution for physiological recording. Recordings were made from neurons in the lateral superior olive (LSO) or medial nucleus of the trapezoid body (MNTB) with glass micropipettes filled with 4 M potassium acetate. 2. Ipsilateral and contralateral synaptic responses were elicited by applying current pulses to the trapezoid body through bipolar stimulating electrodes located at positions lateral and medial to the olivary complex. Both intracellular and extracellular recordings were studied before, during, and after application of drugs to the saline bath containing the tissue slice. 3. Intracellular recordings from 10 neurons in LSO showed that GABA (1-10 mM) caused a concentration-dependent drop in membrane resistance and either reduced or blocked postsynaptic excitatory responses. Similar effects were found in five cells tested with glycine (1-10 mM). Three neurons tested with both GABA and glycine were affected by both drugs. Extracellular spikes were blocked in 53 out of 67 LSO neurons tested with GABA and 29 out of 35 neurons tested with glycine. Seventeen out of 23 neurons tested with both GABA and glycine were affected by both. 4. GABA had a powerful blocking effect on extracellularly recorded action potentials evoked by current-pulse stimulation of the trapezoid body in seven LSO neurons tested after adding the glycine receptor antagonist, strychnine (1 microM), to the bath. GABA also lowered the membrane resistance of one LSO neuron in which intracellular recordings were made in the presence of strychnine. 5. Neurons in MNTB also were affected by GABA and glycine but the proportion of sensitive cells was less than in LSO. GABA reduced membrane resistance in 6 out of 16 neurons and glycine produced a similar effect in 14 out of 26 neurons from which intracellular recordings were made. Six out of 14 neurons tested with GABA and glycine responded to both. Extracellular spikes were eliminated or reduced in amplitude by GABA in 15 out of 44 cells and by glycine in 40 out of 68 cells tested. Eleven out of 29 cells from which extracellular recordings were made were affected by both. 6. The glycine antagonist, strychnine (0.25 - 1.0 muM), blocked both ipsilateral and contralateral inhibitory postsynaptic potentials (IPSPs) in LSO.(ABSTRACT TRUNCATED AT 400 WORDS)

Three-dimensional reconstructions of autonomic projections to the gastrointestinal tract

Three-dimensional reconstruction protocols in confocal microscopy are typically considered in terms of rendering separate stacks of optical sections. Single stacks, however, include volumes that are often too small to permit descriptions of entire neurons, complete axonal arbors, or complex neural networks. Furthermore, traditional tissue preparation protocols generally yield specimens too limited to permit reconstructions of complex neural systems. For 3-D analyses of extensive networks such as the autonomic nervous system projections within the viscera, it is critical to incorporate appropriate tissue techniques, including suitable tracer protocols, into the reconstruction strategy. This report summarizes complementary technologies, including whole mount procedures, tracer techniques for identifying single fibers in situ, and methods of examining stacks of optical images, which make it practical to describe the complete terminal field of an individual axon in the gastrointestinal tract. Such methods establish that vagal motor axons travel long distances within their target organs, collateralize frequently, and ramify extensively. Vagal afferents have extensive, complex, and, in some cases, polytopic arbors within target tissues.

Sound localization after unilateral lesions of inferior colliculus in the ferret (Mustela putorius)

1. The ability of ferrets to localize sounds in space was determined before and after large unilateral lesions of the inferior colliculus. Three animals sustained restricted lesions that destroyed the inferior colliculus caudally but spared some tissue rostrally. These restricted lesions did not extend substantially beyond the cytoarchitectonic boundaries of the inferior colliculus. Four animals received more extensive lesions that destroyed all of the inferior colliculus, including the rostral pole. These lesions also involved to various degrees other midbrain structures, including the dorsal nucleus of the lateral lemniscus and the lateral tegmentum. Psychophysical curves and minimum audible angles were obtained for midline and left and right lateral fields. Comparisons were made of deficits ipsilateral and contralateral to the lesion. 2. The animals were tested in a semicircular apparatus with loudspeakers located at various positions around the periphery. Separate sound localization tests were conducted for midline, left, and right field positions. In each test the animals were trained first to discriminate between speakers separated by 60 degrees. They were then tested with progressively smaller angles of speaker separation to obtain their psychophysical threshold (minimum audible angle). All critical tests of sound localization were based on the ability of animals to identify the location of a 45-ms noise burst presented at the beginning of each trial. Correct responses were rewarded by delivery of a small quantity of water from spouts located around the perimeter of the apparatus. 3. Unilateral lesions restricted to the inferior colliculus had relatively little effect on sound localization. All three animals with restricted lesions were still capable of localizing a single noise burst and minimum audible angles were similar before and after surgery for midline, left, and right field tests. There was no difference in postoperative performance ipsilateral and contralateral to the lesion site. 4. More extensive unilateral lesions that included the dorsal nucleus of the lateral lemniscus and the lateral tegmentum as well as the inferior colliculus resulted in severe deficits in sound localization. Each of the four animals with large unilateral lesions had a substantial impairment in sound localization in the field contralateral to the lesion site. Postoperative performance in the contralateral field was too low to obtain a minimum audible angle for these animals. Midline sound localization was also affected in some cases but ipsilateral sound localization was only slightly affected.

Binaural organization of primary auditory cortex in the ferret (Mustela putorius)

1. The distribution of binaural responses within the ferret's primary auditory cortex was determined by standard microelectrode mapping techniques. Single and multiple unit responses were recorded from the middle ectosylvian gyrus of barbiturate-anesthetized animals with tungsten microelectrodes (1.2-1.8 M omega) inserted into the brain perpendicular to the cortical surface. The characteristic frequency (CF) and binaural response characteristics were determined for each point sampled. 2. Gated pure tones were delivered independently to the two ears through a sealed sound system, and binaural response types were determined by comparison of evoked activity for monaural and binaural stimulation. Most binaural responses fell into one of three major groups: binaural summation (EE/F), binaural suppression (EO/I), or mixed binaural summation and suppression. 3. The neurons tended to be grouped together on the basis of their binaural response properties. Zones of binaural summation and suppression extended across the surface of the middle ectosylvian gyrus and intersected with regions of sound frequency representation. 4. Particular attention was paid to the distribution of binaural responses within isofrequency contours in the ferret's primary auditory cortex (AI). Along the length of each isofrequency contour, areas of EE/F alternated with areas of EO/I. The summation areas were typically between 0.5 and 0.7 mm wide. Single neurons with mixed binaural response properties were frequently found between groups of EE/F and EO/I cells. The mixed responses appeared to mark a transition in location between zones of summation and suppression responses. 5. The distribution of interaural intensity difference (IID) thresholds was also examined along the length of isofrequency contours. No systematic relation was found between IID threshold and the distance along an isofrequency contour.

Physiological evidence for ipsilateral inhibition in the lateral superior olive: synaptic responses in mouse brain slice

The incidence of ipsilateral inhibition in the lateral superior olive (LSO) was examined in a brain slice preparation of the mouse superior olivary complex. A 400 microns brain slice was taken in the frontal plane and maintained in a warm, oxygenated saline solution. Intracellular recordings were made from the LSO with micropipettes filled with 4 M potassium acetate. Synaptic responses were elicited by electrical stimulation of the trapezoid body in different slices at various locations between the cochlear nucleus and the ipsilateral superior olivary complex (SOC). The results show that ipsilateral stimulation can evoke inhibitory as well as excitatory postsynaptic potentials. The ipsilateral IPSPs have short latencies and are elicited by stimulation of the trapezoid body at any point along its course between cochlear nucleus and LSO. Short-latency IPSPs can also be produced by direct stimulation of the ventral cochlear nucleus itself. Ipsilateral IPSPs are blocked by low concentrations of the glycine antagonist, strychnine. In addition, bath application of sodium pentobarbital in one case eliminated ipsilateral IPSPs without eliminating EPSPs. The results suggest that there is a rapidly conducting, glycinergic pathway from cochlear nucleus through the trapezoid body to the LSO on the same side of the brain. This pathway is probably served by either a direct projection from the ventral cochlear nucleus to the LSO or an indirect one from cochlear nucleus to LSO through the lateral nucleus of the trapezoid body (LNTB).

The determination of child custody

This article reviews briefly the history of child custody decision making and describes current custodial arrangements in the United States. It examines both the manner in which parents and courts make decisions regarding custody and access, and the changes in visiting patterns in recent decades. The author discusses the impact of reforms in the law and the implementation of newer dispute resolution and educational interventions, and then makes recommendations for policy and practice.

Response of neurons in the lateral superior olive and medial nucleus of the trapezoid body to repetitive stimulation: intracellular and extracellular recordings from mouse brain slice

The responses of neurons in the lateral superior olive (LSO) and medial nucleus of the trapezoid body (MNTB) to repeated electrical stimulation of the trapezoid body were investigated in a brain slice preparation of the mouse superior olivary complex. Brain slices, 400-500 microns thick, were cut in the frontal plane and were maintained for physiological recording in a bath of warm, oxygenated saline. Both intracellular and extracellular recordings were made with glass micropipettes filled with 4 M potassium acetate. Bipolar stimulating electrodes were placed on the trapezoid body ipsilateral and contralateral to the superior olive. Current levels were set so that an ipsilateral pulse elicited a single action potential in LSO and a contralateral pulse elicited a single action potential in MNTB. Trapezoid body fibers were then stimulated with trains consisting of 10 current pulses. Repeated stimulation at low rates resulted in a number of spikes equal to the number of current pulses. Pulse rate was then increased to determine the limits of response to repeated stimulation. In the MNTB, neurons were capable of following very high rates of stimulation without reduction in response probability. On the average, MNTB neurons responded with a probability of 0.9 at 667 Hz. In contrast, most LSO neurons were incapable of following high rates of stimulation. LSO neurons responded with a probability of 0.9 at 125 Hz. For some LSO neurons, application of strychnine (0.5 microM) to the bath increased the probability of firing at high rates. MNTB neurons were unaffected by strychnine.

Bedside terminals and quality of nursing documentation

In this article, the authors report on part one of a three-part investigation studying the impact of bedside terminals at New York University Medical Center, New York, NY. Using a before-after parallel control-group design, the quality of computerized nursing documentation was studied before and after adding computers to patient rooms. The quality of documentation was defined by timeliness and completeness of data. The study hypothesis, which predicted a positive relationship between the presence of bedside terminals and the quality of nursing documentation, was not supported. Study results showed a minimal use of the computer terminals located in patient rooms. A surprising result was the use of terminals located in rooms other than that of the patient for which documentation was made.

Effects of superior olivary complex lesions on binaural responses in rat auditory cortex

Unilateral or bilateral lesions of the superior olivary complex (SOC) were made by local injection of kainic acid through a micropipette lowered stereotaxically into the rat's auditory brain stem. The lesions had the effect of destroying cell bodies in the superior olive without disrupting fibers of passage. After a recovery period of approximately one month physiological recordings were made with tungsten microelectrodes from the auditory cortex of normal animals and animals with SOC lesions. For animals with unilateral SOC lesions recordings were made either ipsilateral or contralateral to the site of damage. Monaural and binaural tone bursts (110 ms duration) were presented dichotically through a sealed sound delivery system and binaural interaction patterns were determined by comparison of monaural and binaural responses. Some cells were excited by stimulation of either ear and facilitated by binaural stimulation (binaural summation or EE cells), whereas others were excited by contralateral stimulation and inhibited by simultaneous ipsilateral stimulation (binaural suppression or EI cells). Both binaural summation and suppression responses were still present following unilateral SOC lesions. Interaural intensity difference thresholds were within the normal range and no differences were found between animals with lesions placed ipsilateral or contralateral to the recording site. Following a bilateral lesion in one case, both binaural summation and suppression responses were still present. The bilateral lesion had the effect of shifting the average interaural intensity difference thresholds in favor of the contralateral ear. These data suggest that binaural interactions above the level of the superior olive contribute to physiological responses in auditory cortex and that binaural responses in the rat's auditory cortex are shaped by both olivary and supraolivary interactions.

Inhibitory influence of the dorsal nucleus of the lateral lemniscus on binaural responses in the rat's inferior colliculus

The contribution of the dorsal nucleus of the lateral lemniscus (DNLL) to binaural processing was examined by recording single-unit activity in the rat's inferior colliculus before, during, and after a reversible block of the excitatory activity in DNLL by local injection of kynurenic acid. Recordings were made from the central nucleus of the inferior colliculus with glass micropipettes filled with 3 M sodium acetate. Kynurenic acid (2 mM in Locke's solution) was injected into the DNLL through one side of a double-barreled glass pipette. The other side of the pipette was filled with Locke's solution for making control injections and recording neural activity. Pressure injection of 0.7-2.0 microliter of kynurenic acid resulted in the complete cessation of tone-evoked responses in DNLL for periods of 45 min to 1 hr. Tone bursts were delivered separately to the two ears through headphones fitted to the external auditory meatus. Binaural responses in the inferior colliculus were determined by comparing the effects of monaural and binaural stimulation. Attention was focused on neurons that were excited by contralateral stimulation and inhibited by ipsilateral stimulation. Interaural intensity difference (IID) functions were generated by holding contralateral sound pressure constant at 10 dB above threshold while increasing ipsilateral sound pressure level. Prior to kynurenic acid injection, ipsilateral stimulation caused a pronounced suppression of contralaterally evoked single-unit activity. Unilateral injection of kynurenic acid into DNLL reduced the strength of binaural suppression in the contralateral inferior colliculus. In every cell tested, the IID curve in inferior colliculus was shifted following contralateral DNLL injection. The IID curve returned to normal after recovery of neural activity in DNLL. In contrast, no effect was seen in the inferior colliculus ipsilateral to the kynurenic acid injection. The injection of Locke's solution into DNLL had no effect on IID curves in the inferior colliculus. These data suggest that the DNLL plays a role in binaural processing through an inhibitory influence on responses in the contralateral inferior colliculus.

Binaural interaction in the lateral superior olive: time difference sensitivity studied in mouse brain slice

1. The sensitivity of lateral superior olive (LSO) neurons to interaural time differences was examined in an in vitro brain slice preparation. Brain slices, 400-500 microns, were taken through the superior olivary complex of C57 BL/6J mice and were maintained in an oxygenated saline solution for single-unit recording. Both extracellular and intracellular recordings were made with glass pipettes filled with 4 M potassium acetate. Responses were elicited by applying current pulses to the trapezoid body through bipolar stimulating electrodes located ipsilateral or contralateral to the olivary complex. Binaural interactions were studied by manipulating the timing and intensity of paired ipsilateral and contralateral pulses. 2. In extracellular recordings, stimulation of the ipsilateral trapezoid body usually elicited a single action potential, whereas stimulation of the contralateral trapezoid body failed to produce a spike response. Bilateral stimulation resulted in the complete suppression of the evoked spike, indicating the presence of a contralateral inhibitory effect. The degree of inhibition depended on the interpulse interval between ipsilateral and contralateral stimulation. With sufficiently large ipsilateral lead times, the probability of eliciting an extracellular spike was 1.0. As the interpulse interval was gradually shifted to reduce the ipsilateral lead time, the response probability precipitously dropped to 0.0. Most neurons could be completely suppressed by simultaneous stimulation. The dynamic range, defined as the range of interpulse intervals over which response probability changed from 0.9 to 0.1, was between 125 and 225 microseconds for most cells tested. 3. With increasing contralateral lead times, the extracellularly recorded spike was eventually released from inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Kainic acid lesions of the dorsal nucleus of the lateral lemniscus: effects on binaural evoked responses in rat auditory cortex

The effects of unilateral lesions of the dorsal nucleus of the lateral lemniscus (DNLL) on binaural processing were examined by measuring the amplitude of auditory cortical evoked responses in the albino rat. Lesions were made by pressure injection of small quantities of kainic acid through a micropipette lowered into the lateral lemniscus. Comparisons were made between normal animals and animals with unilateral DNLL damage. In normal animals, the amplitude of evoked potentials recorded from left and right primary auditory cortex varied as a function of the time difference between clicks delivered to the two ears. Maximum responses were obtained from the hemisphere contralateral to the leading click, and response amplitude was progressively reduced as the interaural time difference (ITD) was shifted in favor of the ipsilateral ear over the range from +600 microseconds to -600 microseconds. The functions in the left and right hemisphere were symmetrical mirror images of one another. Destruction of the DNLL had no significant effect on the maximum response amplitude, evoked response threshold, or response latency in either hemisphere. On the other hand, the lesion did have the effect of greatly reducing the slope of the ITD function in the hemisphere contralateral to the lesion. The change in slope was attributed to a reduction in the strength of inhibition produced by stimulation of the ipsilateral ear. No effect was seen on the slope of the function in the ipsilateral hemisphere. Animals with lesions that spared DNLL but destroyed the intermediate and ventral nucleus of the lateral lemniscus had normal binaural response functions. These data show that the DNLL plays an important role in shaping binaural responses in the contralateral auditory pathway.

Synaptic pharmacology of the superior olivary complex studied in mouse brain slice

The synaptic pharmacology of the lateral superior olive (LSO) and medial nucleus of the trapezoid body (MNTB) was examined in a brain slice preparation of the mouse superior olivary complex (SOC). Physiological responses in SOC were elicited by electrical stimulation of the trapezoid body ipsilateral or contralateral to the recording site, and bilateral interactions were investigated by combined ipsilateral and contralateral stimulation. Pharmacological effects were tested by bath application of amino acid agonists and antagonists. Neurons in MNTB were excited by contralateral stimulation and unaffected by ipsilateral stimulation. Excitatory amino acid (EAA) agonists--kainic acid (KA), quisqualic acid (QA), or L-glutamate--caused spontaneous firing at low concentrations and eliminated responses at higher concentrations in MNTB. The EAA agonist NMDA had relatively little effect at comparable concentrations. Stimulus-elicited responses were blocked by non-NMDA antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitro-quinoxaline-2,3-dione (DNQX) and by the nonspecific EAA antagonist kynurenic acid, but were unaffected by the NMDA antagonist D,L-2-amino-5-phosphonovaleric acid (APV). LSO neurons were typically excited by ipsilateral stimulation and inhibited by contralateral stimulation. In LSO, KA, QA, and L-glutamate caused spontaneous firing at low concentrations and eliminated responses at higher concentrations, and NMDA had relatively little effect. Excitatory responses in the vast majority of LSO neurons were blocked by CNQX, DNQX, or kynurenic acid. Some responses were also blocked by APV. LSO neurons were affected by glycine, and contralateral inhibition in LSO was completely blocked by strychnine. NMDA also blocked inhibition in LSO. These results indicate that excitation of both MNTB and LSO neurons is mediated primarily by an EAA neurotransmitter through non-NMDA receptors and that contralateral inhibition of LSO cells is mediated through strychnine-dependent glycine receptors. NMDA receptors may play a role in binaural processing by modulating contralateral inhibitory input to LSO.

Binaural responses in rat inferior colliculus following kainic acid lesions of the superior olive: interaural intensity difference functions

The binaural responses of cells in the rat's inferior colliculus were determined following either unilateral or bilateral lesions of the superior olivary complex (SOC). The lesions were made by local injection of kainic acid through a glass micropipette lowered stereotaxically into the auditory brain stem. After a recovery period of at least two weeks, neural responses to pure tone pulses were recorded from the inferior colliculus with tungsten microelectrodes inserted into the central nucleus. Attention was focused on neurons that exhibited binaural suppression, ie., were excited by contralateral and inhibited by bilateral stimulation. Binaural suppression responses were still present following complete unilateral destruction of the superior olive either ipsilateral or contralateral to the recording site. Binaural responses were also present following bilateral lesions of the SOC. Furthermore, the shape and slope of interaural intensity difference functions were not statistically different for normal animals and animals with either unilateral or bilateral SOC lesions. No differences were found among lesion groups or between recording sites ipsilateral or contralateral to the lesions. These data suggest that the superior olive is not essential for binaural interaction and that supraolivary structures play a significant role in shaping binaural responses in the inferior colliculus.

Midline and lateral field sound localization in the ferret (Mustela putorius): contribution of the superior olivary complex

1. The ability of ferrets to localize sound in space was determined before and after unilateral or bilateral lesions of the superior olivary complex (SOC). Lesions were made by pressure injection of kainic acid into the SOC through a stereotaxically positioned glass micropipette. The lesions destroyed the cell bodies in the superior olive without disrupting fibers of passage in the trapezoid body or other pathways in the auditory brain stem. The integrity of fibers was demonstrated by protargol staining of axonal processes and by the retrograde transport of horseradish peroxidase (HRP) from the inferior colliculus to other auditory brain stem nuclei. Behavioral tests were carried out separately for sound localization at midline and lateral field positions. Minimum audible angles were determined for single 45-ms noise bursts presented through paired loudspeakers positioned symmetrically around 0, -60, and +60 degrees azimuth. 2. Four ferrets received complete lesions of the left SOC, and two received complete lesions of the right SOC. In general, unilateral destruction of the superior olive resulted in impairments in sound localization in both left and right lateral fields. In some cases, deficits were also apparent on midline. Four additional animals received unilateral lesions that spared cells within the SOC. In most cases, deficits were apparent despite incomplete lesions of the SOC. The pattern of deficits was generally consistent with that found in animals with complete lesions. Most animals had difficulty localizing sounds in the lateral fields. 3. Four animals received bilateral lesions of the SOC. Three had complete or near-complete destruction of the superior olive on one side of the brain with relatively minor damage on the other side. Each of these animals exhibited behavioral deficits that were particularly severe ipsilateral to the more extensively damaged superior olive. One animal with complete bilateral destruction of the SOC was incapable of sound localization, even with 2-s noise bursts. This animal, however, suffered severe motor impairments after surgery that might have contributed to the apparent inability to localize sound. 4. Two animals with kainic acid lesions that caused little or no damage to the SOC were still capable of high levels of performance in tests of sound localization and had no elevation in minimum audible angles. These cases served as controls for the possible effects of nonspecific brain damage and demonstrated that kainic acid injections per se resulted in no obvious deficits in our test situation.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of continuous noise maskers on tone-evoked potentials in cat primary auditory cortex

In nine barbiturate-anesthetized cats, cortical evoked potentials for tones presented to the contralateral ear were studied for the effects of continuous wideband noise masking. In five animals, input-output functions for tones were obtained in the presence of continuous noise masking at the same ear. Tone thresholds were raised by the presence of the masker, and they closely tracked the level of the masker, such that increments in masker level brought about tone threshold elevations of the same magnitude. In four animals, we compared the effect on responses to contralateral tones of continuous maskers presented to the same ear as the tone, to the opposite ear, and to both ears simultaneously. The presence of the masker at the ear opposite the tone had a small and variable effect on the response to the stimulus at the ear with the tone, whether or not noise was also present at that ear. Consideration of extant single-neuron evidence provides an interpretation of these findings. Whereas maskers at the ear with the tone are known to reduce signal sensitivity for almost all cortical neurons, the effects of masking at the ear opposite the tone (ipsilateral to the cortex) are likely to be very heterogeneous. It is likely that the perceptual salience of signals that have different binaural configurations to concurrent maskers resides in which neuronal elements are activated, rather than in the total number of cells excited, and it is perhaps for this reason that the evoked potentials show only modest effects of this masking parameter.

Effects of superior olivary complex lesions on binaural responses in rat inferior colliculus

Unilateral or bilateral lesions of the superior olivary complex (SOC) were made by local injection of kainic acid through a micropipette lowered stereotaxically into the rat's auditory brainstem. The lesions had the effect of destroying cell bodies in the superior olive without disrupting fibers of passage. After a recovery period of approximately one month, physiological recordings were made with tungsten micro-electrodes from the central nucleus of the inferior colliculus of animals with SOC lesions. For animals with unilateral lesions recordings were made either ipsilateral or contralateral to the site of damage. Results were compared with data from normal control cases. Monaural and binaural tone bursts were presented through a sealed sound delivery system and binaural interaction patterns were determined. Both binaural summation and suppression responses were still present following unilateral SOC lesions. Interaural intensity difference thresholds were within the normal range and no differences were found between animals with lesions placed ipsilateral or contralateral to the recording site. Binaural summation and suppression responses were also present following bilateral lesions. Bilateral lesions had the effect of shifting the average interaural intensity difference thresholds in favor of the contralateral ear. But, in general, binaural interactions were remarkably little affected by bilateral destruction of the SOC.

NMDA, non-NMDA and glycine receptors mediate binaural interaction in the lateral superior olive: Physiological evidence from mouse brain slice

Binaural interaction was investigated in a 400 microns brain slice taken through the mouse lateral superior olive (LSO). Ipsilateral excitatory and contralateral inhibitory inputs to LSO neurons were examined by recording physiological responses to electrical stimulation of the trapezoid body. Bath application of non-N-methyl-D-aspartate (non-NMDA) antagonists blocked ipsilateral excitation and strychnine blocked contralateral inhibition. N-methyl-D-aspartate (NMDA) had little effect on ipsilateral responses but completely blocked contralateral inhibition. These results suggest that ipsilateral excitation is mediated by non-NMDA receptors and contralateral inhibition by strychnine dependent glycine receptors. NMDA receptors may play a role by modulating contralateral inhibition in LSO.

Sound frequency and binaural response properties of single neurons in rat inferior colliculus

Sound frequency and binaural response properties were determined for single neurons in the rat's inferior colliculus. Nerve cell responses in the central nucleus of the inferior colliculus were narrowly tuned and had clearly defined characteristic frequencies (CF). The central nucleus was tonotopically organized with low frequencies represented dorsolaterally and high frequencies ventromedially from 0.87 to 45 kHz. Sharpness of tuning, as indicated by Q10, covered a wide range of values for neurons with the same CF, but the maximum Q10 at each frequency increased monotonically with CF. Maximum Q10s were larger than previously reported for auditory cortex at the same CF. Binaural responses were classified as either suppression, summation or mixed. Most of the units encountered exhibited binaural suppression but there were substantial numbers of both summation and mixed responses. Each major binaural response type was distributed broadly across sound frequencies within the rat's hearing range. Binaural suppression responses were most numerous at high frequencies and summation responses at low frequencies. The binaural response types, their relative proportions and their distribution by CF were similar for neurons in the central nucleus of inferior colliculus and primary auditory cortex of the albino rat.

Pain syndromes in the cancer patient

Paraneoplastic syndromes affect the nervous system in a very small percentage of patients with cancer. In those patients, portions of the nervous system are damaged or destroyed, usually in association with a small and often occult neoplasm elsewhere in the body. Current evidence suggests that these syndromes occur when the body mounts an immune response to an antigen shared between the tumor and the nervous system. The immune attack is then misdirected against that portion of the nervous system that possesses the "onconeural" antigen.