Differential utilization of regulatory domains within the alpha 1(I) collagen promoter in osseous and fibroblastic cells.

Type I collagen is expressed in a variety of connective tissue cells and its transcriptional regulation is highly complex because of the influence of numerous developmental, environmental, and hormonal factors. To investigate the molecular basis for one aspect of this complex regulation, the expression of alpha 1(I) collagen (COL1A1) gene in osseous tissues, we fused a 3.6-kb DNA fragment between bases -3,521 and +115 of the rat COL1A1 promoter, and three deletion mutants, to the chloramphenicol acetyltransferase (CAT) marker gene. The expression of these ColCAT transgenes was measured in stably transfected osteoblastic cell lines ROS 17/2.8, Py-la, and MC3T3-E1 and three fibroblastic lines NIH-3T3, Rat-1, and EL2. Deletion of the distal 1.2-kb fragment of the full-length ColCAT 3.6 construct reduced the promoter activity 7- to 30-fold in the osteoblastic cell lines, twofold in EL2 and had no effect in NIH-3T3 and Rat-1 cells. To begin to assess the function of COL1A1 upstream regulatory elements in intact animals, we established transgenic mouse lines and examined the activity of the ColCAT3.6 construct in various tissues of newborn animals. The expression of this construct followed the expected distribution between the high and low collagen-producing tissues: high levels of CAT activity in calvarial bone, tooth, and tendon, a low level in skin, and no detectable activity in liver and brain. Furthermore, CAT activity in calvarial bone was three- to fourfold higher than that in the adjacent periosteal layer. Immunostaining for CAT protein in calvaria and developing tooth germ of ColCAT3.6 mice also confirmed the preferred expression of the transgene in differentiated osteoblasts and odontoblasts compared to fibroblast-like cells of periosteum and dental papilla. This study suggests that the 3.6-kb DNA fragment confers the strong expression of COL1A1 gene in high collagen producing tissues of intact animals and that the 5' flanking promoter sequence between -3,521 and -2,295 bp contains one or more stimulatory elements which are preferentially active in osteoblastic cells.

Transgenic expression of COL1A1-chloramphenicol acetyltransferase fusion genes in bone: differential utilization of promoter elements in vivo and in cultured cells.

To directly compare the patterns of collagen promoter expression in cells and tissues, the activity of COL1A1 fusion genes in calvariae of neonatal transgenic mice and in primary bone cell cultures derived by sequential digestion of transgenic calvariae was measured. ColCAT3.6 contains 3.6 kb (positions -3521 to +115) of the rat COL1A1 gene ligated to the chloramphenicol acetyltransferase (CAT) reporter gene. ColCAT2.3 and ColCAT1.7 are 5' deletion mutants which contain 2,296 and 1,672 bp, respectively, of COL1A1 DNA upstream from the transcription start site. ColCAT3.6 activity was 4- to 6-fold lower in primary bone cell cultures than in intact calvariae, while ColCAT2.3 activity was at least 100-fold lower in primary bone cells than in calvariae. These changes were accompanied by a threefold decrease in collagen synthesis and COL1A1 mRNA levels in primary bone cells compared with collagen synthesis and COL1A1 mRNA levels in freshly isolated calvariae. ColCAT3.6 and ColCAT2.3 activity was maintained in calvariae cultured in the presence or absence of serum for 4 to 7 days. Thus, when bone cells are removed from their normal microenvironment, there is parallel downregulation of collagen synthesis, collagen mRNA levels, and ColCAT3.6 activity, with a much greater decrease in ColCAT2.3. These data suggest that a 624-bp region of the COL1A1 promoter between positions -2296 and -1672 is active in intact and cultured bone but inactive in cultured cells derived from the bone. We suggest that the downregulation of COL1A1 activity in primary bone cells may be due to the loss of cell shape or to alterations in cell-cell and/or cell-matrix interactions that normally occur in intact bone.

A systematic review and meta-regression of the prevalence and incidence of perinatal depression.

BACKGROUND: Major Depressive Disorder (MDD) is a leading cause of the disease burden for women of childbearing age, but the burden of MDD attributable to perinatal depression is not yet known. There has been little effort to date to systematically review available literature and produce global estimates of prevalence and incidence of perinatal depression. Enhanced understanding will help to guide resource allocation for screening and treatment. METHODS: A systematic literature review using the databases PsycINFO and PubMed returned 140 usable prevalence estimates from 96 studies. A random-effects meta-regression was performed to determine sources of heterogeneity in prevalence estimates between studies and to guide a subsequent random-effects meta-analysis. RESULTS: The meta-regression explained 31.1% of the variance in prevalence reported between studies. Adjusting for the effects of all other variables in the model, prevalence derived using symptom scales was significantly higher than prevalence derived using diagnostic instruments (odds ratio [OR] 1.6, 95% confidence interval [CI] 1.3-2.0). Additionally, prevalence was significantly higher in women from low and middle income countries compared to women from high income countries (OR 1.8, 95% CI 1.4-2.2). The overall pooled prevalence was 11.9% of women during the perinatal period (95% CI 11.4-12.5). There were insufficient data to calculate pooled incidence. LIMITATIONS: Studies in low income countries were especially scarce in this review, demonstrating a need for more epidemiological research in those regions. CONCLUSIONS: Perinatal depression appears to impose a higher burden on women in low- and middle-income countries. This review contributes significantly to the epidemiological literature on the disorder.

1,25-Dihydroxyvitamin D3 inhibition of col1a1 promoter expression in calvariae from neonatal transgenic mice.

We studied the effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) on organ cultures of transgenic mouse calvariae containing segments of the Col1a1 promoter extending to -3518, -2297, -1997, -1794, -1763, and -1719 bp upstream of the transcription start site fused to the chloramphenicol acetyltransferase (CAT) reporter gene. 1,25(OH)2D3 had a dose-dependent inhibitory effect on the expression of the -3518 bp promoter construct (ColCAT3.6), with maximal inhibition of about 50% at 10 nM. This level of inhibition was consistent with the previously observed effect on the endogenous Col1a1 gene in bone cell models. All of the shorter constructs were also inhibited by 10 nM 1,25(OH)2D3, suggesting that the sequences required for 1, 25(OH)2D3 inhibition are downstream of -1719 bp. The inhibitory effect of 1,25(OH)2D3 on transgene mRNA was maintained in the presence of the protein synthesis inhibitor cycloheximide, suggesting that the inhibitory effect on Col1a1 gene transcription does not require de novo protein synthesis. We also examined the in vivo effect of 1,25(OH)2D3 treatment of transgenic mice on ColCAT activity, and found that 48 h treatment caused a dose-dependent inhibition of CAT activity in calvariae comparable to that observed in organ cultures. In conclusion, we demonstrated that 1,25(OH)2D3 inhibits Col1A1 promoter activity in transgenic mouse calvariae, both in vivo and in vitro. The results indicate that there is a 1, 25(OH)2D3 responsive element downstream of -1719 bp. The inhibitory effect does not require new protein synthesis.

Parathyroid hormone represses alpha 1(I) collagen promoter activity in cultured calvariae from neonatal transgenic mice.

We examined the effect of PTH on the activity of alpha 1(I) collagen promoter fusion genes in cultured calvariae from transgenic mice. The parent construct, ColCAT 3.6, contains 3520 basepairs of 5' rat alpha 1(I) collagen DNA, 115 basepairs of untranslated alpha 1(I) collagen-coding DNA, and the bacterial chloramphenicol acetyltransferase reporter gene, while the 5'-deletion ColCAT 2.3 contains 2296 kilobases of rat alpha 1(I) collagen promoter sequence. Transgenic mouse lines harboring these collagen promoter fusion genes were developed using the oocyte microinjection technique, and for each construct, three different lines of mice were tested. Calvariae from 6- to 8-day-old transgenic mice were cultured for 48 h with or without bovine PTH-(1-34). ColCAT 3.6 and ColCAT 2.3 were expressed at comparable levels in calvariae and were inhibited by PTH. There were parallel decreases in the incorporation of [3H]proline into collagen and levels of the endogenous alpha 1(I) collagen mRNA and transgene mRNA. Forskolin at 10 microM mimicked the inhibitory effect of PTH on promoter activity in ColCAT 3.6 and ColCAT 2.3 calvariae. A RNase protection assay showed that the transgene was initiated correctly from the transgene promoter. These data show that PTH and cAMP can repress collagen promoter activity in calvariae from transgenic mice, suggesting that the alpha 1(I) collagen promoter may contain cis elements down-stream of -2.3 kilobases that mediate PTH and cAMP repression of collagen gene expression in bone. Cultured bone explants from transgenic mice can be used as a model to study hormonal regulation of alpha 1(I) collagen promoter constructs.

Interleukin-1 represses COLIA1 promoter activity in calvarial bones of transgenic ColCAT mice in vitro and in vivo.

Interleukin-1 (IL-1) inhibits collagen synthesis in osteoblastic cell lines and primary osteoblast-like cells. However, promoter elements regulating type I collagen A1 (COLIA1) expression in vivo and in organ culture may differ from those regulating expression in cell culture. We have examined the effects of IL-1 on reporter gene activity in neonatal transgenic mouse calvariae bearing COLIA1 promoter-chloramphenicol acetyltransferase (ColCAT) fusion genes. The parent construct, ColCAT 3.6, contains 3.5 kb of 5' flanking sequence and 115 bp of 5' untranslated region fused to the CAT reporter. In 48-h calvarial organ cultures, IL-1 repressed ColCAT 3.6 promoter activity and collagen synthesis in a dose-related manner, with a maximal inhibition of 40-65%. This repression was retained in 5' deletion constructs truncated to-1719 bp. The inhibition of transgene mRNA was blocked by cycloheximide, indicating a requirement for new protein synthesis. Pretreatment with indomethacin diminished the inhibitory effect of IL-1 on CAT activity and collagen synthesis, suggesting partial mediation by prostaglandins. Local in vivo injection of IL-1 (500 ng) decreased calvarial transgene mRNA after 8 h, an effect that was partially blocked by indomethacin. ColCAT transgenic mice represent a useful model for in vitro and in vivo assessment of COLIA promoter regulation by cytokines and other factors.

Regulation of COL1A1 expression in type I collagen producing tissues: identification of a 49 base pair region which is required for transgene expression in bone of transgenic mice.

Previous deletion studies using a series of COL1A1-CAT fusion genes have indicated that the 625 bp region of the COL1A1 upstream promoter between -2295 and -1670 bp is required for high levels of expression in bone, tendon, and skin of transgenic mice. To further define the important sequences within this region, a new series of deletion constructs extending to -1997, -1794, -1763, and -1719 bp has been analyzed in transgenic mice. Transgene activity, determined by measuring CAT activity in tissue extracts of 6- to 8-day-old transgenic mouse calvariae, remains high for all the new deletion constructs and drops to undetectable levels in calvariae containing the -1670 bp construct. These results indicate that the 49 bp region of the COL1A1 promoter between -1719 and -1670 bp is required for high COL1A1 expression in bone. Although deletion of the same region caused a substantial reduction of promoter activity in tail tendon, the construct extending to -1670 bp is still expressed in this tissue. However, further deletion of the promoter to -944 bp abolished activity in tendon. Gel mobility shift studies identified a protein in calvarial nuclear extracts that is not found in tendon nuclear extracts, which binds within this 49 bp region. Our study has delineated sequences in the COL1A1 promoter required for expression of the COL1A1 gene in high type I collagen-producing tissues, and suggests that different cis elements control expression of the COL1A1 gene in bone and tendon.

Upstream regulatory elements necessary for expression of the rat COL1A1 promoter in transgenic mice.

The activity of fusion genes containing fragments of the COL1A1 promoter was measured in tissues from 6- to 8-day-old transgenic mice. ColCAT3.6 contains approximately 3.6 kb (-3521 to 115 bp) of the rat COL1A1 gene, the chloramphenicol acetyltransferase (CAT) reporter gene, and the SV40 splice and polyadenylation sequences. ColCAT2.3 and ColCAT1.7 are deletion constructs that contain 2296 and 1667 bp of COL1A1 upstream from the RNA start site, respectively. For each transgene, up to six lines of mice were characterized. Both ColCAT3.6 and ColCAT2.3 had similar activity in bone and tooth; ColCAT1.7 was inactive. In transgenic calvariae, levels of transgene mRNA paralleled levels of CAT activity. In tendon, the activity of ColCAT2.3 was 3- to 4-fold lower than that of ColCAT3.6, and the activity ColCAT1.7 was 16-fold lower than that of ColCAT2.3. There was little activity of the ColCAT constructs in liver and brain. These data show that DNA sequences between -2.3 and -1.7 kb are required for COL1A1 promoter expression in bone and tooth; sequences that control expression in tendon are distributed between -3.5 and -1.7 kb of the promoter, with sequences downstream of -1.7 kb still capable of directing expression to this tissue. The cis elements that govern basal expression of COL1A1 in transgenic calvariae appear to be different from those required for optimal expression of the COL1A1 promoter in stably transfected osteoblastic cells.

Adenylyl cyclase of perifused porcine granulosa cells remains responsive to pulsatile, but not continuous stimulation with follicle-stimulating hormone.

Differentiation of granulosa cells and development of ovarian follicles requires FSH for several days. The purpose of the present studies was to determine how the capacity of the adenylyl cyclase of immature porcine granulosa cells to respond to FSH depends on the dose, duration, and frequency of exposure to FSH. Cells were stimulated with various regimens of FSH and forskolin in a dynamic flow perifusion system. cAMP production during 4 h of continuous (tonic) exposure to FSH was directly related to FSH concentration (5-500 ng/ml). FSH-stimulated cAMP production declined markedly after 4 h of tonic stimulation with FSH, regardless of the FSH concentration. Preliminary experiments using a pulse interval of 3 h (perifusion medium FSH concentration, 150 ng/ml) indicated that stimulation with 15-min pulses elicited a greater cumulative cAMP response than stimulation with either 5-, 30-, or 60-min pulses. Responsiveness to FSH depended critically on the duration and frequency of stimulation and the concentration of FSH. Short pulses were more effective than long pulses in both eliciting cAMP responses of most uniform amplitude and maintaining responsiveness to a final tonic FSH stimulus. The optimal pattern of stimulation consisted of a pulse duration of 15 min, with a pulse interval of 2-3 h. A peak chamber FSH concentration of 150 ng/ml yielded the greatest cumulative cAMP production, although cells that had been perifused with FSH-free medium had the greatest response to a final tonic FSH stimulus. The attenuation of responsiveness after continuous perifusion with FSH does not appear to be due to desensitization of the cyclase itself, since 1) cells perifused with FSH continuously for 20 h still responded to forskolin (100 microM), which activates cyclase independently of the FSH receptor; and 2) cells did not become refractory to forskolin for 14 h. The transient refractoriness to FSH appears to be due to a process that alters the interaction between the FSH receptor and the guanine nucleotide regulatory component of cyclase. This refractoriness can be reversed simply by removing FSH from the perifusion medium for a critical period of time, i.e. 2-3 h.

Properties of associative long-lasting potentiation induced by cellular conditioning in the motor cortex of conscious cats.

Mechanisms of long-lasting potentiation of synaptic responses induced in the thalamocortical and recurrent collateral pathways of the pyramidal tract were studied in intracellular recordings from the motor cortex of unanesthetized, chronically implanted cats. The observations provide the first description of long-lasting potentiation in the unanesthetized neocortex in vivo. Monosynaptic excitatory postsynaptic potentials of 2-5 mV in amplitude were evoked as test responses by stimulation of the pyramidal tract and thalamic ventrolateral nucleus at 0.1-0.5 Hz frequency. Pressure microinjections of drugs and ions were also performed during intracellular recordings. In the first series of experiments, test synaptic responses were paired with intracellular current injection-induced action potentials at an interstimulus interval set between 0-200 ms and 0.1-0.5 Hz frequency. Pairings (30-100 x) induced long-lasting potentiation of the test responses in 58% of cells. The increased synaptic responses typically initiated action potentials and their potentiation usually lasted over the period of recordings. Increases in amplitude of synaptic responses were not correlated with statistically significant changes in electrical membrane properties (resting potential, input resistance, time constant, spike threshold) or parameters of action potentials and their afterpotentials. The failure to induce increases in synaptic efficacy by unpaired stimuli (pseudoconditioning) demonstrated the associative property of the long-lasting potentiation. In a second series of experiments, differential cell conditioning was employed. This paradigm induced long-lasting potentiation of the explicitly paired synaptic response without noticeable modification of unpaired or pseudorandomly paired synaptic responses tested conjointly in the same neuron. These observations demonstrated the input-specificity of long-lasting potentiation. In a third series of experiments, subthreshold depolarizing current pulses were summated with synaptic responses to induce firing in the recorded neuron during pairing. Long-lasting potentiation occurred in 55% of the summated synaptic inputs. Pseudoconditioning did not induce synaptic potentiation in these cells. In a fourth series of experiments, conditioning was employed in neurons in which firing activity was suppressed by an intracellularly injected lidocaine derivative. Long-lasting potentiation was induced in 50% of the attempts when synaptic responses were paired with current-induced depolarizations greater than 30 mV. These results suggest that postsynaptic induction of long-lasting synaptic potentiation can be successful in the absence of postsynaptic sodium spikes in neurons of the motor cortex in vivo. In a fifth series of experiments, homosynaptic high-frequency tetanization (80-200 Hz for 5-15 s) was applied to the thalamocortical and recurrent pyramidal afferents.(ABSTRACT TRUNCATED AT 400 WORDS)

Electrical properties affecting discharge of units of the mid and posterolateral thalamus of conscious cats.

Discharge properties in response to intracellularly applied, rectangular currents were measured in units of the mid (lateralis dorsalis and centrolateral nuclei) and posterolateral (lateralis posterior and pulvinar nuclei) thalamus of conscious cats. A separate aim was to determine if neuronal excitability changed in association with changes in stimulus-evoked activity after the animals were trained to discriminate between two acoustic stimuli when performing a conditioned motor response. Low threshold spike (l.t.s.) discharges were observed in three of 272 cells given 1 nA intracellular, hyperpolarizing current pulses of 40 ms duration. This finding supports the view that thalamic neurons of conscious animals operate mainly in the relay as opposed to the oscillatory mode. Application of larger and longer hyperpolarizing currents in the cells produced rebound l.t.s. discharges, supporting the expectation that most thalamic neurons are capable of producing this type of discharge. Decrements of spike afterhyperpolarizations (AHP) and broadening of spike bases upon repeated discharge also were observed in each area of the thalamus studied. After conditioning, changes were found in the posterolateral thalamus (but not in the mid-thalamus) in the proportions of cells with spontaneous, rapid (>/=50 Hz), repetitive, discharges (RRD) and rapid, sustained discharges at rates >/=100 Hz during application of depolarizing current (RSD). In the posterolateral thalamus the percentage of units responding to 1 nA depolarization with RSD fell from 71% before conditioning to 45% after conditioning. The percentage of cells with RRD decreased from 69% to 46%. The changes were accompanied by a 3 mV hyperpolarization of the membrane potentials of the cells and a decrease in baseline activity. After conditioning, increases in excitability were found in cells of the mid thalamus that responded selectively to the click conditioned stimulus (CS) that elicited the conditioned response, and decreases in excitability were found in cells of the posterolateral thalamus that responded to the discriminative acoustic stimulus (DS) to which the animals were trained not to respond. An earlier study showed a potentiation of discharge in response to the CS in units of the midthalamus after similar conditioning and a reduction of the proportion of DS responsive units and peak discharge to the DS in units of the posterolateral thalamus. We conclude that the discharge properties of units of the mid and posterolateral thalamus can change to support discrimination between acoustic stimuli of different functional significance after conditioning.

Differences in responses to 70 dB clicks of cerebellar units with simple versus complex spike activity: (i) in medial and lateral ansiform lobes and flocculus; and (ii) before and after conditioning blink conditioned responses with clicks as conditioned stimuli.

Activity was recorded from 554 cerebellar units in eleven conscious cats to determine if responses to 70 dB clicks differed in units with simple and complex spike discharges. Effects of region of recording and behavioral state (with click used as a conditioned stimulus for conditioning) were also assessed. Cells with only simple spikes were distinguished from cells that had the following types of complex spike events: Type I-simple or initial spike followed > 1 ms by multiple spikes with baseline displacement (classical complex spikes), Type II--followed < or = 1 ms by spikes with or without baseline displacement (spikes in the absolute refractory period should arise from a separate site of initiation), and Type III-followed by spikes and displacement too close to the baseline noise to distinguish as Type I or II. Among the groups mean baseline activity was greatest in cells with Type I complex spikes, least in cells with Type III complex spikes, and greater in Type II cells than simple cells. Significant increases in activity within 32 ms of presenting clicks were found in the groups of Type II cells and simple cells. These appear to be the main auditory responsive cells of the cerebellar regions studied. Activity of Type II cells best reflected the temporal properties of the click; responses of simple cells had slower onsets (except in flocculus) and longer durations. Responses to click in Type II and simple cells differed in recordings from: (i) lateral ansiform lobe (lateral crus I and portions of crus II), (ii) medial ansiform lobe (medial crus I), and (iii) flocculus. The largest mean responses above baseline in the first 32 ms after click were found in Type II cells of the lateral ansiform lobe with onsets of 8-16 ms. Magnitudes of response differed before and after conditioning and backward conditioning. In the lateral ansiform lobe, the < 32 ms response to click was greater in Type II than simple cells in each state, but showed a greater increase above baseline after backward conditioning when conditioned responses were not produced than after conditioning. The onset of increased activity to click conditioned stimuli in Type II cells of the lateral ansiform region preceded the onset of the blink conditioned response after conditioning, consisted almost entirely of simple spikes, and reflected an increase in magnitude of response as opposed to an increased number of responsive units. After conditioning, an increased number of units in the flocculus responded to click conditioned stimuli in the 16-24 ms post stimulus period. Of the 16 cells with an onset of increased activity at this time, eight showed only simple spike activity. Seven of the remaining eight cells (all Type II) showed a significant increase in conditioned stimulus-evoked complex spiking above the low (usually < 1/s) baseline level of complex spike discharges. The findings support the conclusions that cerebellar units can respond rapidly enough to acoustic stimuli to play a role in auditory as well as motor processing and that the responses to 70 dB clicks differ among cells with simple and complex spike discharges. The differences are influenced substantially by the region of cerebellar recording and the behavioral state. The findings in cells of the flocculus offer the first evidence that complex as well as simple spike activity can contribute to an increased probability of discharge to click as a conditioned stimulus after conditioning.

TCRB clonotypes are present in CD4+ T cell populations prepared directly from rheumatoid synovium.

The identification of clonal T cells at sites of inflammation is hampered by the large number of polyclonal T cells that nonspecifically accumulate. In this report, we combine the use of T cell sorting with spectratyping of the third complementarity determining region (CDR3) and direct sequence analysis to rapidly screen for and identify clonal expansions of T cells from synovial tissue specimens from patients with rheumatoid arthritis (RA). Initially, we used a polymerase chain reaction specific for the variable region gene of the T cell receptor beta chain (TCRBV) to compare the TCRBV repertoire expressed by CD4+ T cells from the peripheral blood and synovium of five patients with long-standing RA. Each patient had several TCRBV genes that were amplified to a greater degree from synovium. Extensive sequence analysis (n > 170) showed that each patient contained junctional sequences that occurred more than once, implying the presence of T cell clones within the starting CD4+ T cell population. To assess a more straightforward approach to identifying clones, six additional patients were recruited and CD4+, TCRBV2+ synovial T cells were positively selected and analyzed by CDR3 spectratyping. Bands deviating from a normal distribution were excised from the gel and sequenced directly. Clones were detected in half of the patients. These data are consistent with the possibility of an antigen-driven T cell response in RA that remains present in the setting of advanced disease.

Facilitation of acoustic responses of cartwheel neurons of the cat dorsal cochlear nucleus.

Responses to clicks were increased in cartwheel cells of the dorsal cochlear nucleus of cats after pairing presentations of the clicks with local iontophoretic delivery of glutamate. The cells were identified by bursting discharges, and were recorded intracellularly in vivo. The findings indicate that inhibitory interneurons such as cartwheel cells can participate in complex adaptive acoustic signal processing. Each cell displayed doublet discharges of > 800 Hz. In 70% of the cells, some of the doublet discharges reached rates > 1000 Hz.

Identification of short latency auditory responsive neurons in the cat dentate nucleus.

Intracellular recordings of activity in response to acoustic stimuli were obtained from units of the dentate nucleus of conscious cats. Twelve units with short latency responses to 70 dB clicks or hisses were injected intracellularly with biocytin and identified morphologically. The identified cells were small, relatively aspinous, multipolar cells with diameters < 20 microns. Most had beaded dendritic varicosities. Six were located centrally, and five were on the border of the nucleus. One appeared to be an axonal process. The results provide direct evidence that small cells of the dentate nucleus can respond with short latencies of 4-14 ms to acoustic stimuli. We suggest that these cells are part of a primary ascending auditory transmission pathway between cochlear nuclei and the motor cortex.

Response to acoustic stimuli increases in the ventral cochlear nucleus after stimulus pairing.

Recordings of activity in response to click and hiss were made from 364 units of the ventral cochlear nucleus of cats. The unit response to acoustic stimuli increased after forward or backward pairing of the stimuli with glabella tap and hypothalamic electrical stimulation. The results provide evidence against the widely held view that transmission through this initial brain stem relay of the auditory system is invariant, and suggest, instead, that the activity of the ventral cochlear nucleus changes to support increased attentiveness to acoustic signals after variably ordered pairing of conditioned and unconditioned stimuli.

Activation of cells of cochlear nucleus by electrical stimulation of lateral hypothalamus.

Effects of electrical stimulation of the lateral hypothalamus (HS) were examined in 67 cells of the dorsal or ventral cochlear nucleus. Both short latency activity in the 10-20 ms post-stimulus period and late activity in the > 20 ms post-stimulus period were elicited in response to HS. A greater percentage of units exhibited the short latency response in dorsal (89%) than ventral (68%) cochlear nucleus. It was not previously recognized that stimulation of the hypothalamus could elicit increases in spike activity in this auditory relay nucleus. The hypothalamus is known to play a role in visceral-emotional functions, including feeding, fleeing, fighting and reproductive behavior. These results suggest a means by which neural activities supporting these functions could influence acoustic relay transmissions.

Oversized, auditory responsive units of rostral, mid, and posterolateral thalamus.

Activity was recorded from 343 units of rostral, mid, and posterolateral thalamus following a conditioned click stimulus (CS). Over 40% of units responded with increased discharge in cats conditioned to blink to the CS. Twenty-nine units with short latency (less than 40 ms) responses were injected intracellularly with phaseolus lectin and identified morphologically; 83% had long, thick primary dendrites with smaller secondary branches. Almost half (46%) had larger somata than the largest previously described thalamic neurons of this morphologic classification. The results suggest that a previously unidentified class of oversized cells is likely to contain many short latency, auditory responsive units. A substantial number of these cells (36%) projected extrathalamically into the internal capsule, and thus may constitute a new auditory pathway between thalamus and cortex.

Unit activity to click CS changes in dorsal cochlear nucleus after conditioning.

Recordings were made of single unit activity (n = 360 units) from the dorsal cochlear nucleus of cats. Different patterns of activity were elicited by acoustic stimuli before and after Pavlovian conditioning. The peak response to a forward paired click conditioned stimulus (CS) increased whereas that to a backward paired hiss discriminative stimulus (DS) did not. The percentage of units responding to the CS increased from 34% to 46% after conditioning. The findings do not support the widely accepted hypothesis that learning has no effect on transmission through the first brain stem relay of the auditory system and indicate, instead, that the cochlear nucleus can participate in complex adaptive acoustic signal processing.

The dentate nucleus is a short-latency relay of a primary auditory transmission pathway.

Recordings of unit activity showing 4-6 ms latency responses to a click stimulus provided evidence that the dentate nucleus could function as a short-latency auditory relay. On the basis of these findings, plus fiber fillings from injections of phaseolus leucoagglutinin into the dentate, a new auditory pathway between dorsal and ventral cochlear nuclei, dentate nucleus, and rostral thalamus is proposed. The pathway could provide direct, short-latency transmissions to the motor cortex that bypass the classical auditory receptive cortex.