Developmental effect of dimethyl sulfoxide on hypothalamo-neurohypophysial neurons in vitro

Effects of sex and estrogen on tyrosine hydroxylase mRNA in cultured embryonic rat mesencephalon

In order to elucidate cellular events responsible for sex differentiation of the nigro-striatal system, we studied the influence of estrogen on the expression of tyrosine hydroxylase (TH) in sex-specific dissociated cell cultures of embryonic day 14 rat mesencephalon. Cultures were raised in the absence or presence of 17 beta-estradiol (10(-12) M) and hybridized with a [35S]oligonucleotide specific to TH. Cultured cells and tissues were probed for estrogen receptor (ER) transcripts by hemi-nested PCR. More TH mRNA containing cells were present in control cultures from female than from male donors. Estrogen treatment resulted in an up-regulation of TH expression in male cells only and induced a reversal of the sex difference in TH mRNA levels present in early control cultures. ER message was detectable in hypothalamic and uterine tissues but not in mesencephalic tissue or cultured cells. Estrogen exposure failed to induce ER expression in cultured mesencephalic cells. It is concluded that there are sex differences in TH mRNA expression of developing midbrain dopaminergic neurons which are independent of the steroid environment. Estrogen can up-regulate TH mRNA in a sex-specific fashion by modulating signal transduction mechanisms other than the classical nuclear receptor pathway.

New organotypic model to culture the entire fetal rat spinal cord

We have developed a system for culturing separately the entire longitudinally-cut ventral and dorsal parts of the whole spinal cord of 12-14 day rat embryos, either on polylysine-collagen mixture or co-cultured with human muscle. At the time of explanation and throughout the period of culturing (up to 21 days) choline acetyltransferase (ChAT) activity in dorsal macroexplants (D-MEs) was negligible (2% of that in the ventral macroexplants (V-MEs)). During culturing neuronal survival was evaluated by measurements of ChAT and enolase. The densities and lengths of neuronal processes outgrowing from the MEs were measured in living and fixed cultures. In the latter, immunocytochemical and cytochemical stainings, allowing visualization of neurites, were evaluated by computerized video image analysis. The ChAT activity in the MEs cultured under our two experimental conditions differed only during the first few days of culturing, being significantly higher in the V-MEs co-cultured with muscle as compared to those cultured on a polylysine-collagen mixture. After 3 weeks of culturing, ChAT activity was not statistically different. However, the co-cultured muscle fibers definitely influenced: (a) neurite outgrowth, (b) the expression of neurofilament proteins and (c) the ability to maintain cultured MEs long-term. This new system allows study of motor neurons and the influence on them of putative growth, survival and maturation factors in a tissue culture milieu that more closely resembles in vivo conditions than other culture systems. Our established parameters can now serve as a basis for such studies.

fos-lacZ transgenic mice: mapping sites of gene induction in the central nervous system

A transgenic mouse line containing a fos-lacZ fusion gene was derived in which beta-galactosidase activity identified cell populations expressing fos either constitutively or after stimulation. Seizures and light pulses induced nuclear lacZ activity in defined populations of neurons in vivo, and an array of neurotransmitters, including glutamate, induced the transgene in primary brain cultures. In unstimulated mice, the major sites of fos-lacZ expression were skin, hair follicle, and bone. fos-lacZ mice provide a new avenue for activity mapping studies based on gene expression.

Dynamic organization of developing Purkinje cells revealed by transgene expression

The cerebellum has many properties that make it a useful model for investigating neural development. Purkinje cells, the major output neurons of the cerebellar cortex, have drawn special attention because of the availability of biochemical markers and mutants that affect their development. The spatial expression of L7, a protein specific for Purkinje cells, and L7 beta Gal, a gene expressed in transgenic mice that was constructed from the L7 promoter and the marker beta-galactosidase, delineated bands of Purkinje cells that increased in number during early postnatal development. Expression of the transgene in adult reeler mutant mice, which show inverted cortical lamination, and in primary culture showed that the initial expression of L7 is intrinsic to Purkinje cells and does not depend on extracellular signals. This may reflect an underlying developmental map in cerebellum.

Differential effects of delta-9-tetrahydrocannabinol and its 11-hydroxy metabolite on sodium current in neuroblastoma cells

Whole-cell voltage-clamp techniques were used to study the comparative effects of delta-9-tetrahydrocannabinol (THC) and its principal metabolite, 11-hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC), on the voltage-gated sodium current in neuroblastoma cells. The parent compound markedly depressed the inward sodium current with minimal reduction of the outward current, demonstrating that the effects of the drug were related to the membrane potential. In addition, THC reduced the reversal potential, indicating that the drug modified the ion selectivity of the channel. 11-OH-THC similarly depressed inward sodium current; however, in marked contrast to the effects of the parent compound, the drug equally depressed the outward voltage-gated sodium current, indicating that its effects were not related to the membrane potential. Furthermore, 11-OH-THC differed from THC in that it did not alter the reversal potential. The results demonstrate that THC and its 11-OH metabolite both reduce inward sodium current, but their effects on the outward current and ion selectivity are distinctly different. The sum of the actions of these two cannabinoids on the voltage-gated sodium channel provides a plausible cellular basis for THC's depression of action potentials in vivo and for some of its central depressant effects.

A long-term depression of AMPA currents in cultured cerebellar Purkinje neurons

Cerebellar long-term depression (LTD) is a model of synaptic plasticity in which conjunctive stimulation of parallel fiber and climbing fiber inputs to a Purkinje neuron induces a persistent depression of the parallel fiber-Purkinje neuron synapse. We report that an analogous phenomenon may be elicited in the cultured mouse Purkinje neuron when iontophoretic glutamate application and depolarization of the Purkinje neurons are substituted for parallel fiber and climbing fiber stimulation, respectively. The induction of LTD in these cerebellar cultures requires activation of both ionotropic (AMPA) and metabotropic quisqualate receptors, together with depolarization in the presence of external Ca2+. This postsynaptic alteration is manifest as a depression of glutamate or AMPA currents, but not aspartate or NMDA currents. These results strengthen the contention that the expression of cerebellar LTD is at least in part postsynaptic and provide evidence that activation of both ionotropic and metabotropic quisqualate receptors are necessary for LTD induction.

Vasopressin Expression in Cultured Neurons is Stimulated by Cyclic AMP

Abstract Vasopressin and oxytocin genes are expressed in mutually exclusive sets of magnocellular neurons in the hypothalamus. Cell specificity and regulation are probably controlled by extra- and intracellular signals acting on one or the other gene. In order to identify factors that regulate peptide expression, we have used primary dissociated cultures derived from 14-day old foetal rats. Vasopressin expression was monitored by combined immunocytochemistry and in situ hybridization. Treatment of cultures with forskolin and/or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX), both of which result in elevated intracellular cyclic AMP levels, increased the numbers of vasopressin-expressing cells up to 10-fold. The specific Vasopressin messenger ribonucleic acid accumulation was verified quantitatively by ribonuclease protection assays. Forskolin and IBMX did not change the levels of the general neuronal markers, neuron-specific enolase and synaptophysin, suggesting that the effect of these drugs was specific for vasopressin-expressing cells. The drugs were not mitogenic for magnocellular neurons. Furthermore, their effect was not mediated trans-synaptically, as the drugs were also effective in cultures grown in low Ca(2+)/high Mg(2+) medium, as well as in cultures treated with either tetanus toxin or tetrodotoxin. The presence of putative response elements for the transcription factor AP-2 in the 5'promoter regions of all vasopressin genes sequenced so far may provide the molecular basis of the observed cyclic AMP effect. No such elements are present in the genes for oxytocin, the messenger ribonucleic acid levels of which were not measurably affected by forskolin and IBMX in our cultures.

Whole-cell voltage-clamp study of sodium current in neuroblastoma cells: effects of inhibition of neurite outgrowth by colchicine

A method is described for the production of large numbers of neurite-free neuroblastoma cells that are especially suitable for studies involving whole-cell voltage clamp. Differentiation in the presence of colchicine yielded cells having abundant sodium channels, highly reproducible peak currents and no space-clamp problems. Treatment with this drug did not alter the electrophysiological properties of the cells. Colchicine might be similarly advantageous in voltage-clamp studies of different ion channels and other types of cultured neurons.

Development of neurophysin-containing neurons in primary cultures of rat hypothalami is related to the age of the embryo: morphological study and comparison of in vivo and in vitro neurophysins, oxytocin, and vasopressin content

The morphological development of immunocytochemically identified neurophysin neurons and the evolution of neuropeptide content (neurophysins, vasopressin, and oxytocin) were studied in primary cultures of hypothalami obtained from 15- to 19-day-old embryos. According to their perikaryal surface, two populations of neurons were distinguished: large and small cells. Full development (defined by the perikaryal surface) of these neurons was reached at day 21 only in cultures from 15- or 16-day-old embryos. These two types of neurons may correspond to the magnocellular and parvocellular neurons described in vivo. Total neurophysins, vasopressin, and oxytocin content were measured by specific radioimmunoassays. Ontogeny of neurophysins and vasopressin showed a good correlation between cells cultured from 15- to 16-day-old embryos and hypothalami from age-matched rats. However, oxytocin was never detected in any of the cultures whatever the age of the embryos. Under our experimental conditions, hypothalamic primary cultures from 15- to 16-day-old embryos therefore appeared to be suitable for studying the differentiation and regulation of neurophysin- and vasopressin-containing neurons.

Expression of synaptophysin and neuron-specific enolase during neuronal differentiation in vitro: effects of dimethyl sulfoxide

Neural development in dissociated cell cultures of fetal rat brain can be expected to depend on synaptic interactions between cultured neurons. Therefore, an attempt was made to obtain a quantitative measure of the time course of synaptogenesis in such a culture system by assessing the level of the secretory vesicle-associated protein synaptophysin (p38). The developmental schedule of p38 was compared to that of neuron-specific enolase (NSE), an established marker of neuronal differentiation. Cultures were raised from dissociated 14 day-old fetal rat diencephalon. In cultures grown for 1-2 days in vitro (DIV), p38-immunoreactivity was preferentially located in neuronal perikarya. After 10-16 DIV, neurons in culture had formed a dense neuritic network, and almost all of the p38-immunoreactivity occurred in the form of fine punctate deposits associated with neuronal processes that often outlined neuronal cell bodies in a basket-like fashion. Electron-microscopic immunocytochemistry proved the punctate deposits to be presynaptic elements, mostly in the form of axonal varicosities. Quantitative immunoblotting showed that levels of p38 increased from the start of cultivation to DIV 4, stayed fairly constant from DIV 4 to DIV 8, and rose again steeply to peak at DIV 12. In contrast, levels of NSE rose continuously up to DIV 12. After DIV 12, levels of both p38 and NSE fell again. Treatment of cultures with dimethyl sulfoxide (DMSO), an agent known to induce differentiation in various normal and malignant cell types, resulted in a significant increase of p38 levels and in a decrease of NSE levels. The amount of p38 continued to increase beyond DIV 12, whereas NSE diminished after having reached a maximum at DIV 12.(ABSTRACT TRUNCATED AT 250 WORDS)

An immunoblot assay for the simultaneous quantification of several antigens

A radioimmunologic assay method that allows for the simultaneous quantification of several antigens in one sample is described. Polypeptide antigens are resolved electrophoretically and electroblotted to nitrocellulose. The nitrocellulose is then reacted with a mixture of several antisera simultaneously, and antibody-binding proteins are visualized by incubation with 125I-protein A and by autoradiography. Antigens are identified according to their molecular weights and quantified by counting the bound radioactivity. The sensitivity of the assay is in the low nanogram range and can be adjusted individually for each antigen by appropriately diluting the first antiserum. The procedure is presently applied to the detection of three neural antigens, neural cell adhesion molecule, neuron-specific enolase, and synaptophysin, in adult brain tissue and to the assessment of expression of the latter two during development of brain cells in primary culture. The method is fast, comparatively cheap, and associated with a low radiation exposure. It should prove especially useful when only scarce amounts of sample are available.

Developmental changes of neuron-specific enolase and neurofilament proteins in primary neural culture

The expression of neuron-specific enolase (NSE) and neurofilament (NF) proteins in primary dissociated cell cultures derived from 14-day-old fetal rat diencephalon was studied by immunocytochemistry and quantitative western-blot techniques. Both neuronal marker proteins, NSE and NF, can be detected as early as day 2 in vitro. They show pronounced quantitative increases during the time period studied (12 days), the relative change being highest during the first few days in vitro (DIV). The molar ratio of the medium weight NF to the heavy NF polypeptide is 9.1 after 2 DIV and 2.6 after 12 DIV. Phosphorylation of the heavy NF polypeptide increases steadily during cultivation. Comparison of these results to in vivo data reported in the literature suggests that, qualitatively, neuronal development in vitro follows the pattern observed in vivo, but at an accelerated pace.