Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the limbic system of the rat

We used immunocytochemistry to obtain a complete cellular and subcellular mapping of the 1,25-dihydroxyvitamin D3 receptor protein (VDR) in the rat limbic system. We observed specific VDR immunostaining in the nucleus as well as in the perinuclear cytoplasm of neuronal cells. The limbic system consists of a variety of neuronal structures, and is known to have influence on memory, behavior, emotions and reproduction. In the hippocampal formation, we found strong nuclear staining as well as less distinguished cytoplasmic VDR staining in CA1, CA3 and CA4. The CA2 area showed a unique cytoplasmic predominance of VDR. The amygdala was found to exhibit specific patterns of VDR distribution in the various regions of the nucleus. We observed distinct differences of VDR localization within the limbic preoptic areas of the hypothalamus. Further parts of the brain we analyzed included the mammillary bodies, the indusium griseum and the cingulate cortex. The subcellular distribution of VDR in regions of the limbic system suggests a specific functional role of the receptor protein and indicates a role for calcitriol as a neuroactive steroid.

Colocalization of vasopressin and oxytocin in hypothalamic magnocellular neurons in water-deprived rats

The posterior lobe hormones vasopressin and oxytocin are expressed in mutually-exclusive sets of magnocellular hypothamalic neurons. However, under certain functional conditions a partial coexpression has been observed. In the present study we subjected adult rats to long-term osmotic stress by water deprivation for up to 3 days. After 3 days, a marked reduction of vasopressin immunostaining was observed in the paraventricular and supraoptic nuclei as compared with controls. Coexistence of oxytocin and vasopressin occurred in a portion of the magnocellular neurons. Many fibers of the hypothalamic-neurohypophyseal tract contained both peptides. Rehydration for 24 h after 3 days of thirsting resulted in a light recovery of vasopressin immunoreactivity with almost none magnocellular neurons containing both nonapeptides. Our findings indicate that magnocellular hypothalamo neurohypophysial neurons are capable of oxytocin and vasopressin coexpression upon extended osmotic stress.

Low and infrequent expression of nitric oxide synthase/NADPH-diaphorase in neurons of the human supraoptic nucleus: a histochemical study

The gas nitric oxide is a messenger in brain signaling. In the hypothalamo-hypophyseal system nitric oxide is involved in the control of the expression and/or release of peptide hormones (corticotropin-releasing hormone, gonadotropin-releasing hormone, vasopressin and oxytocin). Nitric oxide synthase (NOS), the enzyme generating nitric oxide, is abundantly present in the magnocellular nuclei of the rat hypothalamus. Its localization in the human hypothalamus is less well studied. Hence, we investigated the anatomical distribution of neuronal nitric oxide synthase in the human supraoptic nucleus by use of immunohistochemical and enzyme histochemical techniques. The immunohistochemical localization of NOS was studied in 31 matched human hypothalami (13 control cases, eight depressed patients and ten schizophrenics). NADPH-diaphorase studies were carried out on seven additional hypothalami (three normal brains, four schizophrenics). Apparent inter-individual differences exist with regard to the occurrence of the enzyme in supraoptic neurons. In a majority of cases no immunostaining or histochemical reaction for the enzyme was observed. In seven cases (three controls, two schizophrenics, two depressives) a population of nitrergic nerve cells was seen in the dorsomedial part of the nucleus. This group of cells also stained for NADPH-diaphorase. Also, there were a few NOS-immunopositive neurons scattered throughout the nucleus. Additionally, thin NADPH-diaphorase positive fibers were observed to cross the nucleus. Our data show that, unlike the rat, the human supraoptic nucleus contains only a small number of nitrergic neurons. No correlation was found between the expression of the enzyme in supraoptic neurons and the psychiatric status of the patients.

Coexistence of intestinal trefoil factor (hITF) and oxytocin in magnocellular neurons in the human hypothalamus

Human intestinal trefoil factor hITF, a polypeptide of the P-domain family, was found to occur in hypothalamic neurons. With combined immunofluorescence and immunoperoxidase technique we investigated the coexistence of hITF with the neurohypophysial peptide oxytocin and the associated neurophysin I in sections of the human hypothalamus. In the supraoptic nucleus, 39.2% of magnocellular oxytocinergic perikarya show hITF immunoreactivity. A similar distribution was observed in perivascular hypothalamic oxytocinergic neurons, whereas in the paraventricular nucleus, 99% of the oxytocinergic neurons show hITF coexpression. In the periventricular nucleus (PEV), single, scattered neurons with both immunoreactivities occur. Our findings indicate that hITF and oxytocin are coexpressed in a portion of the magnocellular neurons in the human hypothalamus, and that hITF is among the neurohypophysial peptides.

Tissue transglutaminase in the small intestine of the mouse as a marker for apoptotic cells. Colocalization with DNA fragmentation

Besides the morphological changes in cells undergoing apoptosis, such as chromatin condensation and cell shrinkage, histological demonstration of DNA fragmentation by in situ end labeling (ISEL) has been widely used for the demonstration of apoptotic cells in tissue sections. Although DNA fragmentation can be demonstrated in apoptotic cells and apoptotic bodies in most cases, there is no clear correlation of ISEL staining with apoptosis. It has often been demonstrated that, in many morphologically intact cells, nuclei with fragmented DNA can be found. Thus staining with ISEL for the detection of apoptosis is useful only in connection with other markers for apoptosis as, for example, characteristic morphological changes. Here we show that tissue transglutaminase protein is unequivocally expressed in apoptotic enterocytes as shown by DNA fragmentation and morphology. Tissue transglutaminase is not expressed in enterocytes with healthy morphology, although DNA fragmentation can be demonstrated in these cells. Thus the immunohistochemical demonstration of tissue transglutaminase may serve as a simple marker for apoptotic epithelial cells in tissue sections.

Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the rat olfactory system

1. The rat olfactory system contains numerous target sites for 1,25-dihydroxyvitamin D3, as determined by receptor protein (VDR) immunocytochemistry and in situ hybridization. 2. Nuclear and cytoplasmic VDR immunoreactivity as well as the corresponding hybridization signal was observed in neurons in the olfactory epithelium, the olfactory bulb, and throughout the limbic system in locations also known to be glucocorticoid targets. 3. The widespread distribution of VDR indicates the distinct functional importance of 1,25-dihydroxyvitamin D3 for olfactory perception.

Colocalization of BAX and BCL-2 in small intestine and kidney biopsies with different degrees of DNA fragmentation

Morphological changes associated with apoptosis are closely correlated with the expression of specific proteins. However, the cause-effect relationships between the expression of these proteins and DNA degradation are barely known. For studying expression of apoptosis-related proteins in relation to different degrees of DNA fragmentation, the small intestine with its spatially organized continuum of proliferation, differentiation and death is a very useful preparation. Enterocytes towards the apex of the villi become increasingly susceptible to apoptosis. Here, this "apoptotic gradient" is used to demonstrate the presence of BAX and BCL-2 proteins in the cytoplasm of cells at the onset of apoptosis. In semithin serial sections of the small intestine, BAX, BCL-2 and DNA fragmentation were demonstrated. BAX and BCL-2 are always colocalized and only in cells with fragmented DNA. The gradient of BAX or BCL-2 staining is similar to the gradient of DNA fragmentation. Immunoreactivity for BCL-2 or BAX is most intense in cells that are prone to become apoptotic next in the course of cellular turnover but not in cells in an advanced apoptotic state, showing strongly condensed chromatin. When using the same technique on semithin sections of kidney biopsies, containing epithelia with low cellular turnover, we found DNA fragmentation mainly in the epithelial cells of the distal tubules. Similar to the situation in the enterocytes, BAX staining was confined to the cytoplasm of epithelial cells with a moderate degree of DNA fragmentation and reduced in epithelial cells with a high degree of DNA fragmentation. In contrast to the situation in the small intestine, very low levels of BCL-2 were found. The results suggest that expression of BCL-2 and BAX is related to cell damage as indicated by DNA fragmentation but not to advanced stages of cellular death, as indicated by chromatin condensation and cellular shrinkage.

Distribution of 1,25-dihydroxyvitamin D3 receptor immunoreactivity in the rat brain and spinal cord

A complete mapping study on the 1,25-dihydroxyvitamin D3 receptor immunoreactivity within the rat central nervous system was performed with a monoclonal and a polyclonal antibody. Specific immunostaining was observed within both nuclear and cytoplasmic compartments of a variety of cells in the cerebellum, mesopontine area, diencephalon, cortex, spinal cord, and limbic system. Both monoclonal and polyclonal antibodies provided similar staining patterns. The monoclonal antibody stained distinct domains within the nuclei of all and the cytoplasm of specific neuronal cell types, like motor neurons, Purkinje cells, and pyramidal cells of the cortex more clearly than the polyclonal antibody. The expression of vitamin D3 receptor in the rat central nervous system was confirmed by in situ hybridisation. The widespread distribution of vitamin D3 receptor in distinct portions of the sensory, motor, and limbic brain systems suggests multiple functional properties of 1,25-dihydroxyvitamin D3 in the central nervous system.

Oxytocin pathways mediate the cardiovascular and behavioral responses to substance P in the rat brain

Stimulation of brain periventricular and hypothalamic substance P receptors induces a pressor response and tachycardia associated with mesenteric and renal vasoconstriction and hindlimb vasodilation resembling thus the classical defense reaction. This cardiovascular response is brought about by the activation of the sympathoadrenal system and is accompanied by grooming behavior. To address the role of oxytocinergic pathways in the brain in the mediation of these responses, we investigated the effects of central pretreatment of rats with oxytocin antisense, mixed base, and sense oligodeoxynucleotides on mean arterial pressure, heart rate, and grooming behavior induced by intracerebroventricular injections of substance P (50 pmol). Central pretreatment of conscious rats with the oxytocin antisense oligodeoxynucleotide (intracerebroventricular injections, 8 and 4 hours before administration of substance P) attenuated the mean arterial pressure (by 55%) and heart rate responses (by 58%) as well as grooming behavior induced by the peptide. A complete recovery of all substance P-induced responses was observed 28 hours after antisense oligodeoxynucleotide pretreatment. Intracerebroventricular pretreatment of rats with mixed base and sense oligodeoxynucleotides did not affect the cardiovascular and behavioral responses to substance P. The signal for oxytocin mRNA in the paraventricular nucleus was reduced only in rats pretreated with the antisense oligodeoxynucleotide. These results demonstrate that oxytocin neurons in the paraventricular nucleus, which innervate the cardiovascular centers in the hindbrain and the spinal cord, mediate the increases in blood pressure and heart rate induced by stimulation of substance P receptors in the forebrain. These neurons may also transmit signals, which are generated by substance P in the hypothalamus and are responsible for the sympathoadrenal activation in response to stress.

Apoptosis: correlation of cytological changes with biochemical markers in hormone-dependent tissues

The term apoptosis, also known as programmed cell death (PCD), is used in contrast to necrotic cell death and occurs in various tissues in many different circumstances. In spite of its rather well-defined morphological features, biochemical or physiological characteristics of apoptosis are widely divergent, depending on the cellular system and/or methods in use. Here, we have outlined the current understanding of apoptosis, strictly with regard to its characteristic morphological features, discussing the correlation between morphological changes and biochemical markers.

Coexistence of NADPH-diaphorase with tyrosine hydroxylase in hypothalamic magnocellular neurons of the rat

The presence and distribution of NADPH-diaphorase (ND) neurons as well as tyrosine hydroxylase-immunoreactive (TH) neurons in the hypothalamus are well established. Previous studies have shown the coexistence of ND with neuroactive substances such as calbindin, somatostatin, vasopressin and oxytocin in neurons of this region of the brain. As the tópographical patterns of distribution of ND and TH coincide in many cases, the aim of this study was to determine the possible coexistence of both substances in the main hypothalamic magnocellular nuclei of the albino rat. Histochemical-immunocytochemical double labelling was employed on the same sections as well as a morphometric study. NADPH-diaphorase and tyrosine hydroxylase neurons were observed in all the nuclei under study (supraoptic, paraventricular and accessory nuclei), although most neurons showing the coexistence of both substances were mainly located in the supraoptic nucleus, isolated neurons with double labelling being found in the magnocellular parts of the paraventricular nucleus and in some of the accessory nuclei. Although both substances have previously been shown to be modified in hypothalamic neurons after osmotic stimuli, the range of functions of ND in the CNS is only beginning to be understood. Further studies are needed to elucidate the functional role that ND/TH neurons play in the nervous system.

Rat hypothalamus neuron-like cells in primary culture accumulate and translate mRNA coding for the amphibian P-domain peptide xP1

1. Neurons seem to possess the intrinsic capability to incorporate and translate exogenous RNA. For further evaluation of this phenomenon, we wanted to study the uptake and processing capacity of rat hypothalamic neurons for species-unspecific heterologous cRNA under in vitro conditions. 2. cRNA coding for the amphibian p-domain peptide xP1 was prepared by in vitro transcription and added to the culture medium of rat hypothalamic cells, derived from E18 fetuses. 3. After 2 hr, a fraction of the hypothalamic neuron-like cells had accumulated the radiolabeled transcripts, as could be demonstrated by autoradiographic assessment. Specific immunostaining for xP1 could be demonstrated 18 hr after incubation with the cRNA. 4. Our findings indicate that hypothalamic neuron-like cells are capable of accumulating and translating nonmammalian transcripts. Since it was only a portion of hypothalamic cells that showed this effect, specific recognition sites for RNA may be presented by certain neurons, further supporting the assumption that binding, uptake, and translation of cRNA transcripts represent a general neural property which is malleable to functional status.

1.25-Dihydroxyvitamin D3 receptor is partly colocalized with oxytocin immunoreactivity in neurons of the male rat hypothalamus

With receptor immunocytochemistry, neurons receptive for the steroidhormone 1.25-dihydroxyvitamin D3 have been observed in hypothalamic nuclei. In the present paper we report that a fraction of 1.25-dihydroxyvitamin D3 receptor (VDR) immunoreactive neurons in the hypothalamus of male rats are immunoreactive for oxytocin (OT), suggesting a direct genomic action of this steroid on OT expression. While only 10% of neurons with OT immunofluorescence in the periventricular nucleus contained nuclear VDR immunostaining, up to 50% of the OT neurons in the supraoptic nucleus and 30% in the magnocellular portion of the paraventricular nucleus were VDR positive. VDR immunostaining in the magnocellular nuclei was in many cases confined to the perinuclear cytoplasm. We assume that 1.25-dihydroxyvitamin D3 has effects on hypothalamic peptidergic systems similar to other steroid hormones.

Human intestinal trefoil factor is expressed in human hypothalamus and pituitary: evidence for a novel neuropeptide

Human intestinal trefoil factor, hITF, a secretory polypeptide found mainly in the human gastrointestinal tract, is a member of the newly characterized trefoil factor or P-domain peptide family representing putative growth factors. Here we describe the identification of this gut peptide in the human brain and pituitary. With reverse transcriptase polymerase chain reaction, we were able to isolate and clone the transcript from human hypothalamus. An antibody generated against a synthetic peptide derived from the carboxyl terminus of hITF was used for immunohistochemical studies of appropriate tissue sections. Neurons expressing hITF were identified in two magnocellular hypothalamic nuclei, the paraventricular and periventricular nuclei. hITF polypeptide was also observed in Herring bodies of the neurohypophysis and in secretory cells of the adenohypophysis. Double immunostaining with antigrowth hormone antibody showed partial coexistence in a selected subpopulation of adenohypophysial cells. Localization of hITF in the hypothalamo-neurohypophysial system may suggest a modulatory action on the classical magnocellular nonapeptides vasopressin and oxytocin, and further indicates an adenohypophysial importance of this peptide. It is likely that hITF represents a novel neuropeptide of yet unknown function.

In-situ end labelling with bromodeoxyuridine--an advanced technique for the visualization of apoptotic cells in histological specimens

The fragmentation of nuclear DNA is considered to be a biochemical indication of programmed cell death (PCD) in various tissues. Several light microscopical approaches have been employed for the visualization of such fragmentation and have used either in-situ nick end labelling (ISEL) or in-situ nick translation (ISNT) with labelled dUTP. In the current paper, we can report a new method in which 0.5 micron Epon sections of mouse jejunum were incubated with terminal deoxynucleotidyl transferase (TdT) and 5-bromo-2-deoxyuridine (BrdU) for the in-situ tailing of fragmented DNA. Anti BrdU and the peroxidase anti peroxidase method (PAP) were used for staining the reaction product. Semithin sections of jejunum revealed high resolution images of labelled nuclei in the intestinal mucosa. An examination with confocal laser scanning microscopy indicated the differential distribution of immunoprecipitates in cellular nuclei, perhaps representing those distinct levels of DNA cleavage that may characterise the discrete stages of apoptosis. This new method is likely to offer new possibilities for the high resolution imaging of PCD, including the assessment of time courses and apoptosis statuses in histochemically characterized cells.

Liposomal incorporation changes the effect of 1.25-dihydroxyvitamin D3 on the phospholipase C signal transduction pathway and the eicosanoid cascade on keratinocytes in vitro

1.25-dihydroxyvitamin D3 is of clinical importance (e.g. in the treatment of psoriasis) given its ability to regulate the proliferation and differentiation of human keratinocytes. 1.25-Dihydroxyvitamin D3 mediates its action via genomic and nongenomic pathways. The nongenomic actions begin with the activation of phospholipase C and the subsequent rapid rise in calcium within the cells. We incorporated 1.25-dihydroxyvitamin D3 in liposomes of varying compositions in an attempt to improve their effect/negative side effect ratio. The influence of empty liposomes (1 mM) and free and liposomally incorporated 1.25-dihydroxyvitamin D3 (10 nM) on the rapid release of sulfidoleucotrien and inositole 1,4,5 triphosphate was examined in keratinocytes in vitro. Free 10 nM 1.25-dihydroxyvitamin D3 provoked a rapid rise in sulfidoleucotriens within 30 seconds, followed by a swift decrease in sulfidoleucotrien and inositole 1,4,5-triphosphate concentration after 10 minutes. Empty liposomes and liposomal-incorporated 1.25-dihydroxyvitamin D3 did not show such a strong effect. These results suggest the occurrence of specific binding sites for 1.25-dihydroxyvitamin D3 on the membrane level that are incapable of recognizing 1.25-dihydroxyvitamin D3 trapped within liposomal membrane.

Molecular and cellular analysis of rP1.B in the rat hypothalamus: in situ hybridization and immunohistochemistry of a new P-domain neuropeptide

P-domain peptides, a new family of secretory polypeptides, have been identified mainly in the gastroenteropancreatic tract of humans, rodents, and amphibians as well as in amphibian skin. In the present study, with PCR and RNA analysis a transcript has been discovered in rat brain termed rP1.B. The deduced polypeptide consists of a single P-domain and its amino acid sequence matches that of rat intestinal trefoil factor (rITF). Thus far, rP1.B is the only P-domain peptide expressed in neuronal cells of the CNS. Immunostained magnocellular perikarya were visible in the paraventricular, supraoptic and periventricular nuclei. Parvocellular rP1.B neurons were found in the arcuate nucleus. Additionally, specific hybridization signals with radiolabeled transcripts were observed in the same regions. rP1.B in the rat hypothalamus may be involved in the control of hypothalamo-hypophysial functions.

c-fos mRNA is present in axons of the hypothalamo-neurohypophysial system of the rat

In situ hybridization revealed that c-fos encoding transcripts occur in the median eminence of rats. Osmotic stress resulted within 15 min. in additional labeling of the magnocellular nuclei, while osmotically stimulated rats that had been pretreated with colchicine failed to show c-fos hybridization in the magnocellular perikarya. Rats, pretreated with a polymerase II inhibitor, showed 15 min. after osmotic stimulation c-fos hybridization in the hypothalamic nuclei, whereas the median eminence was depleted of hybridization signal. c-fos is probably among the transcripts, stored in axons of the hypothalamo-neurohypophysial system, to be transported retrogradly upon osmotic stimulation.

Corticotropin-releasing hormone (CRH) antisense oligodeoxynucleotide induces anxiolytic effects in rat

Antisense oligodeoxynucleotide complementary to the start coding region of rat corticotropin releasing hormone (CRH) mRNA was intracerebroventricularly infused into rats three times at 12-h intervals. In the shuttle-box avoidance procedure antisense-treated rats showed, within 6 h, significant acceleration and increase in the total number of discriminative avoidance responses compared with controls, treated with the corresponding sense probe or vehicle alone. Following the shuttle-box experiment hypothalamic CRH hybridization signals and immunoreactivity were reduced, while CRH immunoreactivity in the median eminence remained unchanged. Plasma ACTH and corticosterone were decreased in antisense-treated animals. It is likely that in addition to a selective blockade of CRH translation, antisense treatment may also interrupt secretion of CRH. Antisense targeting of the hypothalamo-hypophysial-adrenal axis may provide new strategies for the neuropharmacology of affective disorders.

Corticotropin-releasing hormone (CRH) antisense oligodeoxynucleotide treatment attenuates social defeat-induced anxiety in rats

1. The neuropeptide corticotropin-releasing hormone (CRH) is the main mediator of the neuroendocrine and behavioral response to stress. End-capped phosphorothioate antisense and sense oligodeoxynucleotides (ODN) corresponding to the start coding region of rat CRH mRNA were infused intracerebroventricularly (30 micrograms/3 microliters per injection) three times at 12 hr intervals. Six hours after the last injection rats were subjected to social defeat stress and subsequently tested on the elevated plus maze. 2. Socially defeated CRH antisense-treated rats displayed markedly reduced anxiety-related behavior, as they spent significantly more time in the open arms of the plus maze compared to sense ODN- and vehicle-treated animals. 3. In controls, social defeat evoked a stress-induced elevation of CRH mRNA and CRH in the hypothalamus and a significant increase in plasma corticotropin (ACTH) levels. These parameters were attenuated in antisense-injected rats. 4. Our results suggest that CRH antisense treatment is effectively suppressing the neuroendocrine and behavioral effects of social defeat.

Antisense oligodeoxynucleotides for in vivo targeting of corticotropin-releasing hormone mRNA: comparison of phosphorothioate and 3'-inverted probe performance

Antisense DNA has been successfully used in vivo to selectively inhibit expression of proteins in the brain. However, stressful side effects after oligodeoxynucleotide (ODN) application have been observed, but not carefully characterized. An attempt was made to establish an animal model of reduced corticotropin-releasing hormone (CRH) activity, using antisense DNA corresponding to the start coding region of rat CRH mRNA with either 3'-3' inverted internucleotidic linkage or with all-phosphorothioate modification. Probes were injected intracerebroventricularly (i.c.v.) twice, 12-hours apart. After phosphorothioate sense ODN injection serum corticosterone levels were significantly elevated compared to vehicle (aCSF) or 3'-3' end inverted sense ODN controls. This increase was also apparent but less pronounced in phosphorothioate antisense treated animals compared with the corresponding sense group. After exposure to ether vapour, both phosphorothioate and inverted antisense ODN injected rats showed a markedly diminished stress induced corticosterone secretion compared to the corresponding sense or vehicle injected rats. These results indicate that a) stress induced corticosterone release is suppressed by i.c.v. CRH antisense treatment, b) phosphorothioate ODNs exert an unspecific, chronic stress-like activation of the HPA-axis and c) this effect is partly inhibited by phosphorothioate antisense directed against CRH mRNA.

Localization of tyrosine hydroxylase mRNA in the axons of the hypothalamo-neurohypophysial system

With in situ hybridization we examined the localization of mRNA coding for tyrosine hydroxylase (TH) in the rat hypothalamo-neurohypophysial system (HNS) under conditions of acute osmotic stress. Fifteen min after salt loading, hybridization signal of TH mRNA could be located in the magnocellular hypothalamic nuclei and in the median eminence (ME). In untreated animals, TH mRNA was detected only in the ME. In osmotically challenged animals that had been pretreated with colchicine, signals for TH mRNA remained confined to the ME, while pretreatment of salt loaded rats with a polymerase II transcription inhibitor resulted in labelling of the magnocellular perikarya but a decrease of the hybridization signal in the ME. Our results suggest that also TH mRNA is among the RNAs which are axonally transported in the HNS. TH mRNA can probably be stored in axons of the hypothalamo-neurohypophysial tract, to be transported retrogradely and translated upon certain stimuli.

Vasopressin antisense oligonucleotide induces temporary diabetes insipidus in rats

The purpose of this study was to downregulate the transcriptional message of arginine vasopressin (AVP) by antisense treatment. A complete phosphorothioate antisense oligodesoxynucleotide corresponding to the beginning of the coding region of rat AVP mRNA was constructed and injected into the lateral ventricle of rats. Within 3-6 h animals exhibited a temporary diabetes insipidus, which lasted up to 9 h. Accordingly, vasopressin immunoreactivity in the hypothalamic nuclei was reduced. Our results demonstrate that a specific and reversible inhibition of neuropeptide expression can be accomplished in the intact hypothalamo-neurohypophysial system by antisense treatment, thus providing a novel tool for studies on stimulus-secretion coupling in vivo.

Ventral tegmental area (VTA) injections of tyrosine hydroxylase phosphorothioate antisense oligonucleotide suppress operant behavior in rats

Dopaminergic A 10 neurons are known to be the essential part of the brain reinforcement system. An antisense oligonucleotide corresponding to the start coding region of rat tyrosine hydroxylase (TH) mRNA, the transcriptional message of the rate limiting enzyme in the metabolic pathway leading to catecholamine synthesis, was constructed and injected into the ventral tegmental area (VTA). 36 h after injection operant behavior was markedly reduced, and this suppression was fully reversed within 5 days following the antisense injection. Accordingly, TH immunoreactivity in the VTA was reduced in comparison to control experiments using mixed bases oligonucleotides. Our results demonstrate that highly specific inhibition of TH expression can be accomplished in the intact mesolimbic system by antisense treatment, thus providing a novel tool for studies on motivational processes in vivo.