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Biomedical subjects

K R Pennypacker

Publications and source records attributed to K R Pennypacker.

At least 37 records · Page 2Linked to original sources
PubMed1996

The effects of dextromethorphan on kainic acid-induced seizures in the rat.

Several studies have shown that dextromethorphan (DM) has both anticonvulsant and proconvulsant effects depending on the animal model. In this study, we examined the effects of DM on three parameters associated with kainic acid (KA)-induced seizures: cell loss in the hippocampus, increased AP-1 DNA binding activity and increased c-Jun and fos-related antigen (FRA) expression. KA administration (8 mg/kg, ip) produced robust behavioral convulsions lasting 4-6 hr. Pretreatment with DM (12.5-75 mg/kg, po) 15 min before KA injections reduced the seizures as well as mortality in a dose-dependent manner. Histological studies revealed a severe loss of cells in the CA1 and CA3 fields of the hippocampus in KA-treated rats. DM pretreatment also reduced this cell loss in a dose-dependent fashion. Biochemical studies showed that DM pretreatment also attenuated the KA-induced increase of AP-1 binding activity and c-Jun/FRA expression in the hippocampus. These results indicate that DM is an effective antagonist of KA.

Animals↗
PubMed1995

Basal expression of 35 kDa fos-related antigen in olfactory bulb.

Recently, there have been a number of reports showing a long-term increased expression of fos-related antigens (fra), molecular weight of 35 kDa, after brain injury or chronic treatment of rats with various drugs. We report elevated basal levels of this transcription factor in the olfactory bulb relative to other brain regions. The expression of this protein is further enhanced in the olfactory bulb as long as 3 months after a single injection of kainate, an effect similar to that we previously observed in the hippocampus. The AP-1 DNA binding activity in olfactory bulb from kainate-treated rats contains fra and jun immunoreactivity suggesting that the 35 kDa fra dimerizes with jun protein, probably junD, to bind to AP-1 sites. Elevated basal levels of this transcription factor in the olfactory bulb appear to be related to the constant reinnervation and synaptogenesis which occurs in this brain region. The 35 kDa fra may be involved in long-term genomic program changes required to adapt to an altered biochemical environment.

Animals↗
PubMed1995

DNA binding activity of CREB transcription factors during ontogeny of the central nervous system.

During the early postnatal period, the rat brain contains high basal levels of AP-1 DNA binding activity which declines to the low levels found in the adult by the third postnatal week. Although the individual transcription factors that comprise this AP-1 DNA binding complex had not been identified, we discovered that these proteins were immunoreactive to the cAMP responsive element binding protein (CREB) and also recognized the CRE element. The 45 kDa CREB-immunoreactive protein was detected at high levels only during the first postnatal week. CRE and AP-1 DNA binding activities were studied in the olfactory bulb, striatum, hindbrain, hippocampus, hypothalamus and cerebellum. In general, the DNA binding activity correlated with the stage of maturation of the particular brain region. However, basal AP-1 DNA binding in the olfactory bulb from adults remained slightly elevated relative to other brain regions. Interestingly, the DNA binding complex in the olfactory bulb began to include fos-related antigen as well as CREB by the third postnatal week. The fra-containing complex only recognizes the AP-1 element, while the CREB complex can bind to either CRE or AP-1 sequences. Thus, there is crosstalk between the signal transduction systems that activate CREB and AP-1 transcription factors. This elevated CREB DNA binding activity may be a sensitive index for studying the development of the brain and could be involved in modulating the genomic program in differentiating cells.

Aging↗
PubMed1995

Acute repeated nicotine injections increase enkephalin and decrease AP-1 DNA binding activity in rat adrenal medulla.

Previously we reported that a single injection of nicotine decreased AP-1 DNA binding activity in adrenal medullae, although chronic bidaily nicotine (and saline) injections increased this binding activity [15]. Repeated acute nicotine injections (3 mg/kg i.p., 7 injections equi-spaced over a 3 h period) effectively increased adrenal tyrosine hydroxylase [3] and [Met5]enkephalin levels and also profoundly decreased adrenal medulla AP-1 DNA binding activity for over 8 h.

Adrenal Medulla↗
PubMed1995

Implications of prolonged expression of Fos-related antigens.

The AP-1 transcription factors are composed of the Fos and Fos-related antigens as well as Jun and related proteins. These factors have been extensively studied in many diverse paradigms using acute stimuli. Recent attention has focussed on long-term elevation of Fos-related antigens in the CNS, and this is discussed by Keith Pennypacker, Jau-S. Hong and Michael McMillian. Repeated or chronic treatment elevates Fos-related antigen levels for days in many different brain regions. Both direct and indirect stimulation are responsible for the protracted increase in Fos-related antigen-immunoreactive proteins, which may modulate late onset genes involved in neuroplasticity. Understanding the role of these factors in long-lasting or permanent disease states may provide insight into potential therapeutic strategies to treat chronic CNS disorders.

Animals↗
PubMed1995

Pharmacological regulation of transcription factor binding.

Organisms respond to extracellular stimuli by changing the expression of genes. Stimulation of the cell often induces a cascade of intracellular events that leads to activation of transcription factor DNA-binding complexes which modulate the transcription rate. Many cellular processes including development of the organism are dependent on these proteins to maintain proper levels of mRNA. A diversity of mechanisms has evolved to coordinate transcription factor binding to the specific DNA element which affects mRNA synthesis. Precise regulatory processes are present at the level of transcription, translation and posttranslation. Often, posttranslational processes alter affinities of factors to DNA-binding sites. In this review, the molecular controls of transcription factor binding to DNA will be examined, with specific examples of the pharmacologic regulation of transcription factor binding to DNA.

Base Sequence↗
PubMed1995

AP-1 transcription factor complexes in CNS disorders and development.

Transcription factors are regulatory proteins that modify gene expression. Any cellular function requiring alterations in mRNA levels depends upon these factors. The CNS, AP-1 (activator protein-1; c-fos and fos-related antigens plus jun-related factors) and CREB (cAMP responsive element binding protein) families of transcription factors have been extensively studied. The DNA binding complex is composed of dimers formed between the AP-1 and CREB factors and binding specificity is dictated by which proteins comprise the complex. Whereas the AP-1 factors are inducible, CREB and related proteins are constitutive and regulate gene transcription through phosphorylation. Due to seizure activity, many AP-1 factors are induced, but rapidly return to basal levels. However, if neuronal death occurs, fos-related antigens of 35 kDa persist for an extended period and may be involved in regulating genes related to neuronal plasticity. Similar factors are expressed after chronic drug treatment indicating a role in drug tolerance. However, during early CNS development, elevated AP-1 DNA binding consisting of c-jun and CREB occurs in every brain region and is inversely related to the degree of maturation of a particular brain area. These transcription factors are important for gene regulation during CNS dysfunction and development and those present specify which genes are activated.

Activating Transcription Factor 2↗
PubMed1994

Regulation of tyrosine hydroxylase in olfactory bulb cultures: selective inhibition of depolarization-induced increase by endogenous opioids.

Regulation of tyrosine hydroxylase (TH) by second messenger pathway activators was examined in rat olfactory bulb cell cultures. The number of TH-immunoreactive neurons was increased 2-3-fold by 36 h treatments with forskolin (Fsk, 10(-6) M) or phorbol myristate acetate (PMA, 10(-7) M), but was not significantly increased by a depolarizing concentration of KCl (45 mM). In contrast, KCl increased media [Met5]enkephalin (ME) immunoreactivity 2-fold in these cultures, equivalent to stimulation with Fsk or PMA. The possibility was examined that ME or another opioid produced by the cultures selectively inhibited the TH response to KCl. Pretreatment with the opioid receptor antagonist naloxone (10(-6) M) greatly increased the number of TH-immunoreactive neurons observed in response to KCl treatment, but had no effect on basal or Fsk-stimulated TH immunostaining, nor on basal or stimulated ME release. The increase in TH-immunoreactivity observed with combined KCl plus naloxone treatment was prevented by pretreating the cultures with the calcium channel blocker nimodipine (10(-6) M), which had no effect on Fsk stimulation or basal TH immunostaining. These data suggest that endogenous opioids selectively inhibit KCl-stimulated Ca2+ entry and thus TH induction in olfactory bulb cell cultures. These cultures offer a simple model system for further study of TH regulation in dopaminergic neurons.

Animals↗
PubMed1994

Brain injury in a dish: a model for reactive gliosis.

Reactive gliosis is a powerful response to brain injury and subsequent neuronal damage in vivo. Neuronal cell cultures are now well established as assays to study this process in vitro. However, equivalent studies of purified glial cell populations have only recently been achieved, following the realization that glial cells produce many of the neuropeptides, transmitters and growth factors that are produced also by neurons. There is now scope for studies in vitro that use mixed, identified populations of glial and neuronal cells to dissect the interactions between the two. Such cultures also lend themselves to assays for potential therapeutic strategies for brain injury that take account of all the different cell types found in the brain.

Animals↗
PubMed1994

Role of a 35 kDa fos-related antigen (FRA) in the long-term induction of striatal dynorphin expression in the 6-hydroxydopamine lesioned rat.

D1 dopamine (DA) receptor agonists induce the expression of the opioid peptide dynorphin (DYN) in the striatum, an effect accentuated several fold by removing the dopaminergic innervation to the striatum (e.g., by lesioning the DA cell bodies in the substantia nigra [SN]). D1 receptor-mediated effects are thought to involve cAMP and/or phosphoinositides as second messengers. However, it is unclear what third messengers are involved in the regulation of DYN expression. The present experiments evaluated the possible role of two families of immediate-early gene (IEG) proteins, Fos and Jun, in the induction of DYN biosynthesis following repeated treatment with DA agonists. In addition, the role of N-methyl-D-aspartate (NMDA) receptors in modulating DA-induced changes in DYN and IEG protein expression was assessed. Adult male rats received unilateral 6-hydroxydopamine (6-OHDA) or sham lesions of the SN. Following a recovery period, animals were injected twice daily with the DA agonist, apomorphine (APO; 5 mg/kg), for 4 or 7 days. As expected, APO induced DYN biosynthesis, at both the peptide and mRNA level, several fold more in the striatum ipsilateral to the 6-OHDA lesion than in the contralateral control side (or a sham lesioned striatum). These effects appeared to be mediated by D1 receptors since the D1 agonist, SKF 38393 (5 mg/kg), caused the same changes in DYN expression as APO whereas a D2 agonist, quinpirole (1 mg/kg), had no effect. Paralleling the increase in DYN expression, APO also induced the expression of c-Fos and Fos-related antigens (FRA's), in particular a 35 kDa FRA, but had no effect on the expression of various Jun-related IEG proteins (i.e., c-Jun, Jun B, Jun D). Consistent with the notion that Fos and FRA proteins alter transcriptional activity by binding to AP-1 (or AP-1-like) DNA sequences in the promoter regions of target genes, we found that repeated APO treatment caused large increases in AP-1 binding activity in striata ipsilateral to 6-OHDA lesions. These data indicate that repeated activation of D1 receptors increases both the expression of a 35 kDa FRA and AP-1 binding, events which may mediate the large increases in DYN expression in the DA denervated striatum. While co-administration of the NMDA receptor antagonist, MK-801, inhibited APO-induced increases in DYN and Fos/FRA expression in the intact striatum, its only effect in the DA-denervated striatum was a partial (35%) inhibition of the APO-induced increase in DYN-ir concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1994

Ontogeny of kainate-induced gene expression in rat hippocampus.

The ontogeny of kainate induction of AP-1 mRNAs, proteins, and DNA binding activities was examined in the rat hippocampus. In addition, kainate induction of preproenkephalin and preprodynorphin mRNAs was examined; these genes have been shown to be induced by kainate and have been suggested to be targets of AP-1 regulation in adult rat hippocampus. Despite producing seizures at postnatal day (P) 7, kainate failed to induce AP-1 or opiate gene expression and did not increase AP-1 DNA binding activity at this age. Basal levels of AP-1 and opiate mRNAs were low in P7 hippocampus. Basal levels of c-jun protein and AP-1 DNA binding activity were elevated in the P7 hippocampus, to values greater than induced levels in adult hippocampus. Furthermore, AP-1 DNA binding in P7 hippocampal nuclear extract was unaffected by antibodies against fos-related antigens, in contrast to hippocampal extracts from the older rats examined. At P14, induction of AP-1 and preproenkephalin (but not preprodynorphin) mRNAs was observed with kainate treatment, but the time course for inductions was delayed relative to kainate inductions in the adult hippocampus. At P21, responses to kainate were similar to the adult response. Unlike in adult hippocampus, seizure activity caused by kainate treatment does not increase the transcription factor and opioid peptide gene expression in the hippocampi of P7 rats.

Animals↗
PubMed1994

Pharmacological regulation of AP-1 transcription factor DNA binding activity.

The AP-1 transcription factor family consists of two groups of proteins, fos-related antigens (fra) and jun proteins. These transcription factors are usually expressed at low basal levels but they can be dramatically induced in a variety of cell types by many different stimuli, in which the quantity of AP-1 transcription factor and the DNA binding activity also rise. The quantity and DNA binding activity of transcription factors are not always at low levels. For example, early in brain development a high basal expression of AP-1 DNA binding activity exists. Similarly, adult rat adrenal gland contains high levels of AP-1 DNA binding activity whose regulation appears to be through post-translational modification (i.e., phosphorylation). Thus, AP-1 DNA binding activity is modulated in a developmental and tissue-specific manner.

Adrenal Glands↗
PubMed1994

Prolonged expression of AP-1 transcription factors in the rat hippocampus after systemic kainate treatment.

Systemic administration of kainate, a glutamate receptor agonist, caused neuronal death in the CA1 and CA3 fields of the rat hippocampus. In the areas of cell loss, reactive astrocytes increased their expression of an astrocyte-specific protein, glial fibrillary acidic protein (GFAP). AP-1 DNA binding activity and the expression of a 35 kDa fos-related antigen (fra) remained elevated in the rat hippocampus for at least 2 weeks after a single systemic injection of kainate, which correlated with changes in gene expression during reactive gliosis. Immunoreactivity for fras was detected in the nuclei of neurons in the dentate gyrus, but relatively few cells in CA1 and CA3 were immunoreactive 1 week after kainate treatment. However, elevated AP-1 DNA binding activity was observed in the CA1 and CA3 regions as well as in the dentate gyrus, suggesting that proteins other than the fras were involved in the astrocytic AP-1 complex. The AP-1 DNA binding activity in hippocampus recognized an AP-1 sequence from the promoter region of the GFAP gene, suggesting that GFAP is a potential target gene. Thus, a single systemic injection of kainate causes long-term activation of AP-1 DNA binding activity in the rat hippocampus and may be important for long-term changes in gene expression in hippocampal cells.

Animals↗
PubMed1993

Elevated basal AP-1 DNA binding activity in developing rat brain.

Nuclear extracts from hippocampi, striata and hypothalami of postnatal day (P) 7 rats contained elevated basal levels of AP-1 DNA binding activity and c-jun protein, which decreased to the low basal levels observed in the adult by P21. In contrast to the AP-1 DNA binding complex in the adult brain, the fos-related antigens were not a major component of the P7 AP-1 DNA binding activity.

Aging↗
PubMed1993

Kainate-induced changes in opioid peptide genes and AP-1 protein expression in the rat hippocampus.

In the rat hippocampus, jun, c-fos, and fos-related antigen immunoreactivity, AP-1 DNA binding, and opioid peptide gene expression were examined after kainate treatment to determine whether the induction and DNA binding of AP-1 transcription factors are correlated with the expression of the opioid peptide genes. One and one-half hours after kainate administration, fos-related antigen and jun immunoreactivity and AP-1 DNA binding were induced; maximal elevation was observed after 4.5 h. Transcription factor expression and DNA binding increased in a dose-dependent manner. Preprodynorphin and preproenkephalin mRNA induction was also dose dependent. The anticonvulsants, pentobarbital and diazepam, effectively blocked electroencephalographic seizure activity caused by kainate treatment, whereas valproic acid was approximately 50% effective. Opioid peptide gene expression, fos-related antigen and jun immunoreactivity, and AP-1 DNA binding all reflected similar reductions after anticonvulsant treatment. Therefore, expression and DNA binding activity of the AP-1 transcription factors are correlated with opioid peptide gene expression in the rat hippocampus.

Animals↗
PubMed1992

Characterization of dynorphin-containing neurons on dissociated dentate gyrus cell cultures.

In the dentate gyrus, the synthesis of the opioid peptide, dynorphin, is modulated by a variety of stimuli. In order to elucidate the cellular and molecular mechanisms regulating the synthesis of dynorphin in the hippocampus, we have established a routine primary cell culture of dentate granule neurons and identified granule-like neurons by a characteristic marker, dynorphin, in these cultures. Cultures were prepared from 7-day-old rat pups and maintained in medium with 2% fetal bovine serum. These cultures contained approximately 20% neurons and survived for over 4 weeks. After 2 weeks in culture, neurons expressing dynorphin-A and its messenger RNA were detected using immunocytochemistry and in situ hybridization, respectively. In dentate cultures, enkephalin-, cholecystokinin-, neuropeptide Y- and substance P-positive cells were observed in addition to dynorphin-positive cells with immunocytochemistry. The results suggest that dentate gyrus cell cultures provide a valid in vitro model for studying molecular mechanisms regulating prodynorphin gene expression.

Animals↗
PubMed1992

Preferential activation of [3H]phorbol-12,13-dibutyrate binding by AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) in neonatal striatal cell cultures.

Activation of excitatory amino acid receptors increased [3H]phorbol-12,13-dibutyrate ([3H]PdBu) binding in four week cultures of striatal cells from postnatal day 7 rat pups (PN7), and in PN7 cells co-cultured the fourth week with striatal cells from postnatal day 1 rat pups. Kainate (KA), trans-1-amino-cyclopentyl-1,3-dicarboxylate (ACPD), and N-methyl-D-aspartate (NMDA) increased [3H]PdBu binding equally in both types of cultures, but alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) increased binding by 3-fold in the co-cultures. Thus, [3H]PdBu binding in these two types of striatal cultures offers a simple model system for studying the regulation of AMPA/KA receptor responses.

Animals↗