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D W Pfaff

Publications and source records attributed to D W Pfaff.

At least 325 records · Page 18Linked to original sources
PubMed1985

Actions of feeding-relevant agents on hypothalamic glucose-responsive neurons in vitro.

Effects of three feeding-relevant agents on the single-unit activity of the hypothalamic ventromedial nucleus (VMN) were investigated with tissue slice preparations. Changes in ambient glucose concentrations altered the activity of 39% of the 129 VMN neurons recorded. The predominant effect of glucose was facilitation. Norepinephrine (NE) affected all of the 29 glucose-responsive neurons tested, but only some (33/47) of the neurons unresponsive to glucose. Unlike that of glucose, the effects of NE on neuronal activity were distributed across excitatory, inhibitory, or biphasic responses. In vivo estrogen treatment did not affect neuronal responses to glucose, it modulated the type of neuronal responses to NE from glucose-responsive, but not glucose-unresponsive neurons. These results indicate that glucose, NE, and estrogen act on a common, glucose-responsive, population of VMN neurons but, as judged from their effects on neuronal activity, through different cellular mechanisms. Accordingly, glucose-responsive neurons may serve to integrate information mediated by different feeding-relevant agents.

Animals↗
PubMed1985

Possible role for endogenous oxytocin in estrogen-facilitated maternal behavior in rats.

Intracerebroventricular (i.c.v.) infusions of oxytocin (OXY) induce short-latency maternal behavior in estrogen-primed virgin rats. To investigate if brain OXY might have a role in the onset of maternal behavior at parturition, we have used both antisera to OXY and an analog antagonist of OXY, d(CH2)5-8-ornithine-vasotocin, to reduce the activity of endogenous OXY in a pregnancy-terminated preparation which yields reliable short-latency maternal behavior. Sprague-Dawley rats with lateral ventricle cannulae were ovariectomized and hysterectomized on day 16 of gestation; maternal behavior was stimulated by a s.c. injection of estradiol benzoate (EB). Effects of the i.c.v. infusion of antisera to OXY or of the i.c.v. infusion of d(CH2)5-8-ornithine-vasotocin on the latency to respond to pups were tested by presenting pups 48 h after surgery and EB treatment. Behavioral observations were made for the next 5 h and periodically over the next 5 days. Groups receiving either the antisera to OXY or the analog antagonist had significantly longer latencies to respond to pups than did control groups. In a separate experiment, i.c.v. infusion of d(CH2)5-8-ornithine-vasotocin was shown to have no effect on the performance of maternal behavior in lactating rats 5 days postpartum. These results suggest that OXY may have a role in promoting short-latency maternal behavior in steroid-primed female rats, but that it is probably not involved in sustaining this behavior during lactation.

Animals↗
PubMed1985

A subset of beta-endorphin- or dynorphin-containing neurons in the medial basal hypothalamus accumulates estradiol.

We used the combined steroid autoradiography-immunocytochemical method to determine whether estradiol- or dexamethasone-concentrating cells contain endogenous opioid peptides. Ovariectomized-adrenalectomized female rats were given highly radioactive doses of 3H-estradiol or 3H-dexamethasone, then sacrificed to demonstrate nuclear steroid binding. Autoradiograms were prepared, exposed for 2-12 months, photodeveloped, and fixed; immunocytochemistry was carried out on the same sections using antibodies to beta-endorphin or dynorphin A (1-17). In the medial basal hypothalamus, many estradiol- and some dexamethasone-concentrating neurons were found intermingled with beta-endorphin or dynorphin-immunoreactive neurons. Of the beta-endorphin-immunoreactive neurons in the medial basal hypothalamus, 4% concentrated estradiol in their nuclei. In addition, a subset of beta-endorphin-immunoreactive cells in the anterior pituitary concentrated estradiol in their nuclei. Although none of the beta-endorphin-immunoreactive neurons in the medial basal hypothalamus concentrated dexamethasone in their nuclei, many of the beta-endorphin-immunoreactive cells in the anterior pituitary did. Of the dynorphin-immunoreactive neurons in the medial basal hypothalamus, 10% concentrated estradiol in their nuclei. These data are consistent with the hypothesis of a genomic effect of estradiol on a particular subset of medial basal hypothalamic neurons that produce endogenous opioid peptides.

Adrenalectomy↗
PubMed1984

Localization of forebrain neurons which project directly to the medulla and spinal cord of the rat by retrograde tracing with wheat germ agglutinin.

Wheat germ agglutinin (WGA) in a slow-release polyacrylamide gel pellet was implanted in the medulla or spinal cord of the rat. Large numbers of retrogradely labeled cells were visualized by immunocytochemical procedures in specific nuclei of the forebrain mainly ipsilateral to the implant site following implants as far caudal as the sacral segments of the spinal cord. Total average number of labeled forebrain cells (three brains per category; 100 micron per 150 micron of brain tissue were examined microscopically): medulla, 2,115; cervical, 1,878; lumbar, 1,017; sacral, 385. After WGA-gel implants in the medulla or cervical cord the majority of retrogradely labeled neurons were seen in the lateral hypothalamic area, the zona incerta, and in subdivisions of the paraventricular nucleus. A continuum of labeled cells extended from the caudal part of the paraventricular nucleus into the posterior hypothalamus and into the central gray of the midbrain. Labeled cells were also seen in the medial basal hypothalamus and the rostral part of the bed nucleus of the stria terminalis. A few labeled cells were observed in the medial and lateral preoptic areas, the rostral part of the paraventricular nucleus, and in the arcuate nucleus. Following WGA-gel implants in the lumbar or sacral cord many retrogradely labeled cells were observed mainly in the paraventricular nucleus, the lateral hypothalamus, zona incerta, medial basal hypothalamus, and posterior hypothalamic area. The continuum of labeled cells described above was also seen following these implants. Our data indicate that the lateral hypothalamus and zona incerta, as well as specific parts of the paraventricular nucleus, are major loci of neurons which project directly to the medulla and spinal cord of the rat. The consistency with which labeled cells were localized across all brains examined within categories of implant sites and the large numbers of labeled cells counted within these areas appeared to verify the sensitivity of our retrograde tracing method. Therefore, we interpret the paucity or absence of labeled cells in particular brain regions to indicate that cells of these regions do not project to the medulla or spinal cord.

Amygdala↗
PubMed1984

Temporal pattern of HRP spread from an iontophoretic deposit site and description of a new HRP-gel implant method.

In the course of examining afferents to ventromedial hypothalamic (VMH) neurons using horseradish peroxidase (HRP), we needed to know how close to an iontophoretic deposit site neurons could be proved to be retrogradely labeled. In evaluating cells near but clearly outside HRP deposit sites visualized after a 24-hour survival period, for example, neurons which had been filled with HRP by somal or dendritic uptake could not be treated as retrogradely labeled and thus would not add to studies of intrahypothalamic connections. Rats were given standardized iontophoretic applications of HRP into VMH (continuous positive current 0.25 mu amp for 1 minute) and sacrificed after 5 or 15 minutes, 1, 4, 8, 12, or 24 hours in order to examine the pattern of HRP spread. The chromogen was tetramethylbenzidine. The volume of the application site visualized at 24 hours was less than 10% of maximum site size, which occurred at 1 hour. Since the cells located within the maximal spread boundary are candidates for nonretrograde labeling, HRP data on local connections obtained even from small iontophoretic deposits must be evaluated in the light of the demonstrated expansion and subsequent contraction of the application site. These results may also hold implications for the precision with which distant connections can be examined using the HRP retrograde method, as sites that appear discrete when visualized after 24-hour survival may have overlapped at shorter times post-iontophoresis. Incorporation of retrograde tracers into polyacrylamide gels provides an effective alternative to pressure injection or iontophoresis of aqueous tracer solutions. We describe a method for filling micropipettes with HRP-polyacrylamide gel. The pipettes are then implanted into brain sites to provide a confined pool of HRP. With postimplantation survival of 24 hour or longer, this method produces sites comparable in size to iontophoretic sites examined at 24 hours and results in improved retrograde labeling. Some results obtained with this method concerning the afferent connections of the dorsomedial hypothalamus are described.

Animals↗
PubMed1984

Segmental organization of rat lateral longissimus, a muscle involved in lordosis behavior: EMG and muscle nerve recordings.

Following stimulation of lumbar cutaneous and high threshold muscle afferents in urethane-anesthetized ovariectomized rats, polysynaptic multi-unit responses were recorded from muscle nerves to lateral longissimus (LL) at a mean latency of 9.5 ms. These responses could be reciprocally evoked between segments with no apparent rostro-caudal asymmetry. Polysynaptic responses habituated to repeated stimulation within 0.5-1.5 min but could be evoked again after several minutes rest. In estradiol-treated rats, 60% of the 9.5 ms responses were followed by late discharges (greater than 40 ms) as compared to 24% in untreated control animals (P = 0.05). Following stimulation to the L3 and L4 motor nerves to lateral longissimus, EMG responses were recorded from overlapping fields of innervation. The conduction velocity of the fast muscle fibers was determined to be 7 m/s. The short length of most of the LL muscle fibers and the intersegmental recruitment of LL motoneurons by cutaneous afferents is compatible with the integrated action of axial muscles in the performance of lordosis behavior.

Animals↗
PubMed1984

Suprachiasmatic neurons in tissue slices from ovariectomized rats: electrophysiological and neuropharmacological characterization and the effects of estrogen treatment.

Single-unit activity and unit responses to putative neurotransmitters were recorded from suprachiasmatic nucleus (SCN) neurons in brain tissue slices from ovariectomized rats either treated or untreated with estrogen. Altogether, 204 units were studied from estrogen-treated and untreated preparations, and at the resting state, 37% of these units fired regularly, 57% fired irregularly, and 6% were silent but evokable by electrical stimulation. Most of the irregular units fired continuously (n = 100), while the rest fired intermittently (n = 12) or phasically (n = 4). Neurons with different types of firing patterns also varied significantly in resting firing rate and in responsiveness to transmitters and to estrogen treatment. The average resting firing rate decreased significantly from regular, irregular and continuous, intermittent, to silent units. Acetylcholine (ACh) and/or serotonin (5-HT) injected directly into the perfusion chamber evoked responses from more irregular (69% of 61 units) than regular units (20% of 46 units). None of the 5 silent units tested was activated by ACh or 5-HT. Responses to ACh (predominantly inhibitory) and 5-HT (predominantly excitatory) seen here in vitro were opposite to those observed in vivo with iontophoretic application, and were not reversed or abolished by the blockade of synaptic transmission. Comparisons of data between the two types of preparations showed that only the responsiveness of the irregular units to ACh and to 5-HT were significantly different: both types of responsiveness were higher in estrogen-treated than in untreated preparations. No significant difference was found in the responsiveness of regular units, or in firing patterns or firing rate. Thus, the present in vitro studies have demonstrated that SCN contains a heterogeneous population of neurons distinguishable by their electrophysiological and neuropharmacological characteristics, and that estrogen has a specific action on specific types of SCN neurons.

Acetylcholine↗
PubMed1984

Alteration by estrogen of the nucleoli in nerve cells of the rat hypothalamus.

Estrogen is accumulated from the blood by nerve cells in the ventromedial nucleus of the hypothalamus and can facilitate female reproductive behavior by acting on this region of the brain. This cell group was examined in ovariectomized female rats, given estrogen or control treatment, by use of light and electron microscopy. A significantly greater portion of the nerve cells in the estrogen-treated animals had protuberances on their nucleolar surfaces, apparent under the light microscope. The fine structure of such protuberances included dense, aggregated material, which is shown to contain DNA by the sodium tungstate staining technique. Because increased numbers of such protuberances were found in nuclei of cells of the experimental group where previous studies demonstrated a significant increase in ultrastructural signs of biosynthetic activity, they may be associated with increased RNA synthesis. Thus, they could indicate, ultrastructurally, increased synthetic rates for RNA in nerve cells through which estrogen promotes reproductive behavior.

Animals↗
PubMed1984

Axial electromyogram and intervertebral length gauge responses during lordosis behavior in rats.

Electromyogram activity from transversospinalis (TS) and lateral longissimus (LL) muscles was recorded concomitant with resistance changes of an intervertebral length gauge during manually elicited lordosis performance. Subjects were estrogen-treated ovariectomized rats. The EMG activity was evoked by manual stimulation of the cutaneous fields contacted by the male rat during mounting. During bilateral palpation of flanks at 2/s, time-locked bursts of EMG activity or more generalized EMG activation was recorded. The EMG response was accompanied by continuous and cumulative length gauge shortening, reflecting progressive rump elevation. The earliest recorded length gauge response had a latency of 10 ms from the first flank stimulus in a sequence of repetitive palpations. Perineal pressure recruited motor units in both the TS and LL which fired at high frequency. The latencies of EMG responses from the TS tended to be briefer than those from the LL; 24/35 TS responses were within 50 ms of the onset of perineal pressure. During some lordoses, the EMG response in both muscles was substantially briefer than the duration of the pressure stimulus and of the length gauge response. Activation of axial muscles during postural adjustments, standing, turning, and other behaviors is also reported. These data represent the first analysis of axial EMG and vertebral length gauge recordings during an endocrine-dependent mammalian behavior.

Animals↗
PubMed1984

Oxytocin induction of short-latency maternal behavior in nulliparous, estrogen-primed female rats.

This study was designed to test whether intracerebroventricular (icv) administration of oxytocin can shorten the latency of estrogen-treated virgin rats to respond to foster pups with maternal care. A secondary goal was a description of the behavioral effects of icv oxytocin in rats. Forty-eight hours before pup presentation female rats (Sprague-Dawley strain, obtained from Zivic-Miller Laboratories, Inc.) with chronic lateral ventricle cannulae were ovariectomized and treated with 100 micrograms/kg body wt estradiol benzoate (EB). Immediately before pup presentation either 400 ng oxytocin or the normal saline vehicle was infused. A second control group of noncannulated animals received the same surgery, EB treatment, and behavior tests without any icv infusion. Maternal behavior was scored on a scale from 0 to 5, one point each being given for licking pups, carrying pups, grouping pups, crouching over pups, and nest building. At the end of 1 hr of pup exposure 65% of the oxytocin-infused animals received scores of 4 or 5, while only 25% of the control animals attained these scores. Maternal behavior appeared as a unit in both spontaneously maternal and oxytocin-treated animals, with fewer than 10% in either group receiving scores of 1, 2, or 3. The oxytocin group also spent significantly more time grooming. In a second experiment in which oxytocin or normal saline was administered icv to oil-treated animals, this grooming effect was shown to be estrogen independent while the induction of maternal behavior required prior treatment with estrogen. Finally, a slight, transient hyperthermic effect of oxytocin on body temperature was observed in this test paradigm. These data suggest a role for oxytocin, acting with estrogen, in the onset of maternal behavior in rats.

Animals↗
PubMed1984

Axonal projections and peptide content of steroid hormone concentrating neurons.

The axonal projections of cell groups containing the most dense collections of steroid hormone concentrating cells have been demonstrated with retrograde neuroanatomical tracing methods. Horseradish peroxidase revealed large numbers of neurons in ventrolateral ventromedial nucleus (VL-VM) which project to dorsal midbrain. Wheat germ agglutinin (immunocytochemical recognition method) revealed large numbers of neurons in medial basal hypothalamus (MBH) and particular subdivisions of paraventricular nucleus (PVN) that project to dorsal caudal medulla or spinal cord. Fluorescent dyes revealed that many preoptic area (POA), anterior hypothalamic (AHA), and bed nucleus of the stria terminalis (BNST) neurons project to ventral tegmental area of Tsai (VTA). Also many neurons in POA and BNST project to amygdala. A method which enabled simultaneous demonstration of the steroid binding capacity and axonal projections of neurons in the same tissue section revealed that 26-36% estradiol (E2) concentrating cells in VL-VM project to dorsal midbrain. E2 concentrating neurons in POA and BNST project to amygdala and E2 concentrating POA neurons project to VTA. These neurons, which send their axons to cell groups located in different brain regions, are probably under the genomic-regulatory influence of E2. Using a method which allows simultaneous demonstration of peptide content and steroid hormone concentrating capacity of cells, many oxytocin-neurophysin and vasopressin-neurophysin containing magnocellular neurons in the caudal PVN were found to concentrate E2. About 4% of the beta-endorphin and about 6% of the dynorphin containing neurons in the MBH concentrate E2. In contrast, virtually none (less than 0.2%) of the LHRH containing hypothalamic neurons concentrate E2.

Amygdala↗
PubMed1984

On-line data acquisition system using an Apple computer: ISI and PST histograms.

A combined hardware/software system for the study of the temporal distributions of spike data is described. Through extensive use of assembly language subroutines the program is able to simultaneously acquire, analyze and display the incoming data. Production of a "Temporal Memory Map" makes possible the examination of acquired data at a wide variety of different bin widths. Interaction with the user is made extremely simple. Provisions are included for the labelling and printing of the output histograms and for the compact storage of data onto floppy disks. Maximum temporal resolution is 0.1 millisecond and maximum total acquisition width is 12.8 minutes. Hardware requirements beyond the basic computer consist of an external signal conditioning circuit and a slot-independent peripheral card containing two integrated circuits. The system has been successfully used in the analysis of neural and EMG evoked responses and should be widely useable in other applications.

Computers↗
PubMed1984

RNA and protein synthesis inhibitors: effects on sexual behavior in female rats.

Biochemical evidence indicates that many steroid hormone effects on target tissues are mediated via actions on the genome. Studies on the hormonal control of reproductive behavior have demonstrated several effects of RNA or protein synthesis inhibitors on female sexual behavior in rats. In female rats treated with estrogen and progesterone, intracranial application of actinomycin-D (an RNA synthesis inhibitor) can disrupt lordosis responding if the drug is given in conjunction with estrogen, but not with progesterone. Protein synthesis inhibitors (cycloheximide or anisomycin) applied intracranially at the time of estrogen also disrupt lordosis, with anisomycin antagonizing the progesterone-facilitation of lordosis. Possible neural sites of action of these drugs are considered, as are alternative modes of action of these synthesis inhibitors. Whereas the effects of estrogen on lordosis include the synthesis of some, as yet unidentified, proteins, the exact role for protein synthesis in the mediation of progesterone's actions on lordosis remains less certain.

Animals↗
PubMed1984

Ultrastructure and enzyme digestion of nucleoli and associated structures in hypothalamic nerve cells viewed in resinless sections.

Estrogen has been shown to affect ventromedial hypothalamic (VMH) nerve cell nucleoli in ovariectomized rats, by causing an increase in the number of electron-dense aggregates associated with nucleoli. In order to characterize these nucleolus-associated structures and other nuclear components, we examined the ultrastructure of ventromedial hypothalamic nucleoli and nuclei revealed by enzyme digestions (pepsin, RNase and DNase) in resinless thin sections. Digestion by pepsin did not cause obvious alterations in the morphology of the nucleolus or its related structures. Pepsin treatment followed by RNase, however, reduced the density of the nucleolus, while that of the nucleolus-associated structure and other related structures remained unchanged. Conversely pepsin treatment followed by DNase, reduced the density of nucleolus-associated and other chromatin structures, but had no effect on the density of the nucleolus. Pepsin treatment followed by RNase and then DNase treatment, reduced the density of the nucleolus and nucleolus-associated structures. A residual nucleolus and nucleolus-associated structure remained after this treatment. Stereo viewing of resinless sections shows that the nucleolus, its associated structures, and other related structures, are associated with fine filaments that may comprise the nuclear matrix. The nucleolus-associated structure containing DNA may direct RNA synthesis at an increased rate in estrogen-treated hypothalamic cells.

Animals↗
PubMed1984

Brain stem reticular influences on lumbar axial muscle activity. I. Effective sites.

Lumbar axial muscle responses to electrical stimulation of the brain stem reticular formation were used to characterize reticular influences on these muscles. Electromyographic recordings were obtained from the transversospinalis, medial longissimus, and lateral longissimus systems in the urethan-anesthetized rat. Ipsilateral stimulation of the pontomedullary reticular formation evoked excitatory responses in these muscles. Trains of pulses were required, but currents as low as 15 microA were effective. Contralateral reticular stimulation with currents similar to those that elicited activation during ipsilateral stimulation at the same brain stem levels could inhibit lumbar electromyographic activity. The results suggest that the motoneurons innervating the lumbar axial musculature in the rat receive strong reticulospinal influences that could be important for postural maintenance and the expression of certain behaviors.

Animals↗
PubMed1984

Brain stem reticular influences on lumbar axial muscle activity. II. Temporal aspects.

Epaxial muscle electromyographic (EMG) responses to electrical stimulation of the pontomedullary reticular formation were analyzed for temporal patterns in the urethan-anesthetized rat. Recordings were obtained from the transversospinalis, medial longissimus, and lateral longissimus groups of back muscles. In response to a series of repetitive stimulus trains, the latency of muscle activation decreased with successive trains. Typically a 10-fold decrease in latency required eight to nine stimulus trains (5 trains/s, 25 pulses/train) with currents of 25-30 microA. Individual pulses within long stimulus trains evoked muscle spike potentials at low probability but with short latencies (population range 4-7 ms). The results suggest that whereas influences on lumbar axial musculature from brain stem reticular formation were not powerful enough to evoke muscle spikes with single-pulse stimulation at currents applied in this study, they can yield short, relatively fixed EMG onset latencies in response to individual pulses within stimulus trains once a potentiation phenomenon has occurred.

Animals↗
PubMed1984

Prolactin mRNA exists in rat hypothalamus.

Using radiolabeled DNA complementary to rat pituitary prolactin mRNA, we probed RNA gel blots from three rat tissues: pituitary, hypothalamus, and liver. Poly (A)-enriched RNA from male and female hypothalami contained a hybridizable RNA which was the same size as, though less abundant than, mature pituitary PRL mRNA. These results support the proposal that the rat brain synthesizes PRL.

Animals↗