preproenkephalin and Body-Weight

Epidemiological studies have shown a link between sleep loss and the obesity 'epidemic,' and several observations indicate that sleep curtailment engenders positive energy balance via increased palatable-food 'snacking.' These effects suggest alterations in reward-modulatory brain systems. We explored the effects of 10 days of sleep deprivation in rats on the expression of striatal opioid peptide (OP) genes that subserve food motivation and hedonic reward, and compared effects with those seen in hypothalamic energy balance-regulatory systems. Sleep-deprived (Sleep-Dep) rats were compared with yoked forced-locomotion apparatus controls (App-Controls), food-restricted rats (Food-Restrict), and unmanipulated controls (Home-Cage). Detection of mRNA levels with in situ hybridization revealed a subregion-specific upregulation of striatal preproenkephalin and prodynorhin gene expression in the Sleep-Dep group relative to all other groups. Neuropeptide Y (NPY) gene expression in the hippocampal dentate gyrus and throughout neocortex was also robustly upregulated selectively in the Sleep-Dep group. In contrast, parallel gene expression changes were observed in the Sleep-Dep and Food-Restrict groups in hypothalamic energy-sensing systems (arcuate nucleus NPY was upregulated, and cocaine- and amphetamine-regulated transcript was downregulated), in alignment with leptin suppression in both groups. Together, these results reveal a novel set of sleep deprivation-induced transcriptional changes in reward-modulatory peptide systems, which are dissociable from the energy-balance perturbations of sleep loss or the potentially stressful effects of the forced-locomotion procedure. The recruitment of telencephalic food-reward systems may provide a feeding drive highly resistant to feedback control, which could engender obesity through the enhancement of palatable feeding.

Topics: Animals; Body Weight; Eating; Enkephalins; Fasting; Insulin; Leptin; Male; Neostriatum; Nerve Tissue Proteins; Neuroimaging; Neuropeptide Y; Opioid Peptides; Protein Precursors; Rats; Rats, Sprague-Dawley; Reward; Sleep Deprivation; Up-Regulation

The developing neuroendocrine brain represents a potential target for endocrine active chemicals. The UV filter 4-methylbenzylidene camphor (4-MBC) exhibits estrogenic activity, but also interferes with the thyroid axis. We investigated effects of pre- and postnatal exposure to 4-MBC in the same rat offspring at brain and reproductive organ levels. 4-MBC (7, 24, 47 mg/kg/day) was administered in chow to the parent generation before mating, during gestation and lactation, and to the offspring until adulthood. mRNA of estrogen target genes involved in control of sexual behavior and gonadal functions was measured by real-time RT-PCR in ventromedial hypothalamic nucleus (VMH) and medial preoptic area (MPO) of adult offspring. 4-MBC exposure affected mRNA levels of ER alpha, progesterone receptor (PR), preproenkephalin (PPE) and insulin-like growth factor-I (IGF-I) in a sex- and region-specific manner. In order to assess possible changes in sensitivity of target genes to estrogens, offspring were gonadectomized on day 70, injected with estradiol (E2, 10 or 50 microg/kg s.c.) or vehicle on day 84, and sacrificed 6 h later. The acute induction of PR mRNA, and repression (at 6 h) of PPE mRNA by E2 was enhanced by 4-MBC in male and female VMH and female MPO, whereas male MPO exhibited reduced responsiveness of both genes. Steroid receptor coactivator SRC-1 mRNA levels were increased in female VMH and MPO. The data indicate profound sex- and region-specific alterations in the regulation of estrogen target genes at brain level. Effect patterns in baseline and E2-induced gene expression differ from those in uterus and prostate.

Topics: Animals; Body Weight; Brain Chemistry; Camphor; Endocrine Disruptors; Enkephalins; Estradiol; Female; Gene Expression Regulation; Genes, src; Litter Size; Male; Molecular Sequence Data; Orchiectomy; Organ Size; Ovariectomy; Preoptic Area; Protein Precursors; Rats; Rats, Long-Evans; Receptors, Estrogen; Receptors, Progesterone; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sex Characteristics; Thyroid Gland; Thyroid Hormones; Ventromedial Hypothalamic Nucleus

Cholinergic interneurons of the striatum respond to motivationally relevant stimuli and are involved in appetitive learning. However, there has been relatively little inquiry into the role of striatal acetylcholine in food motivation. Here we show in rats that a single infusion of the muscarinic receptor antagonist scopolamine (0, 5.0 or 10.0 microg/0.5 microL bilaterally) potently reduced 24-h food intake following injections into either the ventral or dorsal striatum, without affecting water intake. Furthermore, muscarinic receptor blockade induced reliable and widespread reductions in striatal preproenkephalin, but not preprodynorphin, mRNA expression. These data suggest a novel role for striatal acetylcholine in modulating feeding behavior via its effects on enkephalin gene expression. As prior research indicates a critical role for striatal enkephalin in consummatory behaviors and palatability, we hypothesize that cholinergic interneurons assist in translating hypothalamic energy state signals into food-directed behaviors via their regulation of striatal opioid peptides.

Topics: Animals; Behavior, Animal; Body Weight; Corpus Striatum; Dose-Response Relationship, Drug; Drug Administration Schedule; Eating; Enkephalins; Gene Expression; In Situ Hybridization; Locomotion; Male; Muscarinic Antagonists; Nerve Tissue Proteins; Protein Precursors; Rats; Rats, Sprague-Dawley; Scopolamine; Time Factors

Various hypothalamic neuropeptides are involved in central regulation of food intake and expression of genes encoding these peptides changes with alterations in the bodyweight/metabolic status/nutritional status. Orexin(s) and dynorphin have been implicated in the regulation of appetite and neuroendocrine systems, but the function of these peptides is not well understood. We have employed in situ hybridization to examine the effects of long-term alterations in the bodyweight on expression of mRNA for preproorexin and prodynorphin in the putative feeding centers of the ovine hypothalamus. Expression of preproorexin was localized to the dorsomedial hypothalamic nucleus, perifornical area and lateral hypothalamic area. Cells expressing prodynorphin were localized to the periventricular, supraoptic, paraventricular, ventromedial hypothalamic nuclei and the thalamus. Small numbers of single scattered cells were seen in other brain areas. A few scattered prodynorphin-expressing cells were found in the lateral hypothalamic area but, in contrast to observations in the rat, there was no colocalization with preproorexin. Long-term alterations in the bodyweight did not influence the level of expression of preproorexin or prodynorphin. These findings suggest that orexin and dynorphin may not play a direct role in appetite regulation in sheep, although regulation at the level of the receptors for these peptides remains a possibility.

Topics: Animals; Appetite Regulation; Body Weight; Carrier Proteins; Dynorphins; Enkephalins; Feeding Behavior; Female; Food Deprivation; Gene Expression Regulation; Hypothalamus; Intracellular Signaling Peptides and Proteins; Neurons; Neuropeptides; Neurosecretory Systems; Orexins; Ovariectomy; Protein Precursors; RNA, Messenger; Sheep; Time Factors

Environmental manipulations early in life may induce persistent alterations in adult behaviour and physiology. The underlying neural mechanisms of these responses are not yet clear. We have previously reported long-term changes in brain opioid peptide levels in male and female Sprague-Dawley rats after short periods (15 min, known as neonatal handling) of maternal separation (MS) until weaning. To study this further, we investigated behavioural and neurochemical effects of repeated MS in male Wistar rats. The rat pups were separated from their dams in litters for either 360 min (MS360) or 15 min (MS15) daily from postnatal day 1 to 21 or exposed to normal animal facility rearing. Behavioural analysis showed that MS360 rats had increased ultrasonic calls on postnatal day 5 compared to MS15 rats, but not on postnatal day 6. Moreover, the MS360 rats had more animals with higher frequency of calls at day 5 than 6 than the MS15 rats. Analysis of the opioid peptides dynorphin B and Met-enkephalin-Arg(6)Phe(7) with radioimmunoassay 7 weeks after the MS procedure, revealed long-term neurochemical changes in several brain areas and in the pituitary gland. Immunoreactive dynorphin B and Met-enkephalin-Arg(6)Phe(7) levels were affected in the hypothalamus and dynorphin B levels in the neurointermediate pituitary lobe, amygdala, substantia nigra and the periaqueductal gray. Together, these findings show that repeated periods of MS early in life in male Wistar rats affect the development of the ultrasonic call response and induce long-lasting and possibly permanent alterations in the opioid peptide systems.

Topics: Animals; Animals, Newborn; Behavior, Animal; Body Weight; Brain; Corticosterone; Dynorphins; Endorphins; Enkephalin, Methionine; Enkephalins; Female; Male; Maternal Deprivation; Opioid Peptides; Pituitary Gland; Protein Precursors; Radioimmunoassay; Rats; Rats, Wistar; Time Factors; Ultrasonics

Brain opioid peptide systems are known to play an important role in motivation, emotion, attachment behaviour, the response to stress and pain, and the control of food intake. Opioid peptides within the ventral striatum are thought to play a key role in the latter function, regulating the affective response to highly palatable, energy-dense foods such as those containing fat and sugar. It has been shown previously that stimulation of mu opiate receptors within the ventral striatum increases intake of palatable food. In the present study, we examined enkephalin peptide gene expression within the striatum in rats that had been given restricted daily access to an energy-dense, palatable liquid food, chocolate Ensure(R). Rats maintained on an ad libitum diet of rat chow and water were given 3-h access to Ensure(R) daily for two weeks. One day following the end of this period, preproenkephalin gene expression was measured with quantitative in situ hybridization. Compared with control animals, rats that had been exposed to Ensure(R) had significantly reduced enkephalin gene expression in several striatal regions including the ventral striatum (nucleus accumbens), a finding that was confirmed in a different group with Northern blot analysis. Rats fed this regimen of Ensure(R) did not differ in weight from controls. In contrast to chronic Ensure(R), acute ingestion of Ensure(R) did not appear to affect enkephalin peptide gene expression. These results suggest that repeated consumption of a highly rewarding, energy-dense food induces neuroadaptations in cognitive-motivational circuits.

Topics: Animals; Blotting, Northern; Body Weight; Cacao; Cognition; Corpus Striatum; Dietary Sucrose; Eating; Enkephalins; Food, Formulated; Gene Expression Regulation; In Situ Hybridization; Male; Motivation; Nucleus Accumbens; Protein Precursors; Rats; Rats, Sprague-Dawley

Progress in the control and treatment of pain may be facilitated by a better understanding of mechanisms underlying nociceptive processing. Here we show that mice subjected to an intermittent fasting diet (IFD) display markedly reduced responses in models of thermal and visceral pain compared with mice fed ad libitum (AL). Pharmacological analyses suggest that a change in the endogenous kappa-opioid system underlies IFD-induced analgesia. The levels of prodynorphin mRNA and kappa-opioid receptors in the spinal cord are higher in IFD than in AL mice. Furthermore, in spinal cord nuclear protein extracts, the activity of the transcriptional repressor DREAM (downstream regulatory element antagonist modulator), the main regulator of prodynorphin expression, is lower in IFD than in AL mice. Finally, c-Fos expression in dorsal spinal cord after noxious stimulation is significantly lower in IFD than in AL animals, indicating that dynorphin could block nociceptive information at the spinal cord. These results suggest that dietary restriction together with administration of kappa-opioid agonists could be useful as a new therapeutic approach for pain relief.

Topics: Analgesia; Animals; Behavior, Animal; Body Weight; Enkephalins; Fasting; Male; Mice; Motor Activity; Naloxone; Narcotic Antagonists; Pain Measurement; Protein Precursors; Reaction Time; Receptors, Opioid, kappa; Spinal Cord

A spontaneous point mutation in the coding region of the carboxypeptidase E (CPE) gene results in a loss of CPE activity that correlates with the development of late onset obesity (Nagert, J. K., Fricker, L. D., Varlamov, O., Nishina, P. M., Rouille, Y., Steiner, D. F., Carroll, R. J., Paigen, B. J., and Leiter, E. H. (1995) Nat. Genet. 10, 135-142). Examination of the level of neuropeptides in these mice showed a decrease in mature bioactive peptides as a result of a decrease in both carboxypeptidase and prohormone convertase activities. A defect in CPE is not expected to affect endoproteolytic processing. In this report we have addressed the mechanism of this unexpected finding by directly examining the expression of the major precursor processing endoproteases, prohormone convertases PC1 and PC2 in Cpe(fat) mice. We found that the levels of PC1 and PC2 are differentially altered in a number of brain regions and in the pituitary. Since these enzymes have been implicated in the generation of neuroendocrine peptides (dynorphin A-17, beta-endorphin, and alpha- melanocyte-stimulating hormone) involved in the control of feeding behavior and body weight, we compared the levels of these peptides in Cpe(fat) and wild type animals. We found a marked increase in the level of dynorphin A-17, a decrease in the level of alpha-melanocyte-stimulating hormone, and an alteration in the level of C-terminally processed beta-endorphin. These results suggest that the impairment in the level of these and other peptides involved in body weight regulation is mainly due to an alteration in carboxypeptidase and prohormone convertase activities and that this may lead to the development of obesity in these animals.

Topics: Amino Acid Sequence; Animals; Aspartic Acid Endopeptidases; Body Weight; Brain; Carboxypeptidase H; Carboxypeptidases; Endorphins; Enkephalins; Feeding Behavior; Mice; Mice, Knockout; Organ Specificity; Peptide Fragments; Pituitary Gland; Point Mutation; Pro-Opiomelanocortin; Proprotein Convertase 1; Proprotein Convertase 2; Proprotein Convertases; Protein Precursors; Reference Values; Subtilisins

Parkinson's disease (PD) is associated with a progressive loss of dopamine neurons in the substantia nigra and degeneration of dopaminergic terminals in the striatum. Although L-DOPA treatment provides the most effective symptomatic relief for PD it does not prevent the progression of the disease, and its long-term use is associated with the onset of dyskinesia. In rodent and primate studies, glial cell line-derived neurotrophic factor (GDNF) may prevent 6-OHDA- or MPTP-induced nigral degeneration and so may be beneficial in the treatment of PD. In this study, we investigate the effects of GDNF on the expression of dyskinesia in L-DOPA-primed MPTP-treated common marmosets, exhibiting dyskinesia. GDNF or saline was administered by two intraventricular injections, 4 weeks apart, to MPTP-treated, L-DOPA-treated common marmosets primed to exhibit dyskinesia. Prior to GDNF or saline administration, all animals displayed marked dyskinesia when treated with L-DOPA. GDNF administration produced a significant improvement in motor disability and, following the second injection of GDNF, a significant improvement in the locomotor activity was observed. Following the administration of L-DOPA there was a greater reversal of disability and a reduction in the intensity of L-DOPA-induced dyskinesia in GDNF-treated animals compared to saline-treated controls. However, there was no significant difference in L-DOPA's ability to increase locomotor activity between GDNF-treated and saline-treated animals. GDNF treatment caused a significant increase in the number of tyrosine hydroxylase-positive neurons in the substantia nigra, but no change in [(3)H]mazindol binding to dopamine terminals was found in the striatum of GDNF-treated animals compared to saline-treated controls. In GDNF-treated animals a small but significant reduction in enkephalin mRNA was observed in the caudate nucleus but not in the putamen or the nucleus accumbens. Substance P mRNA expression was equally reduced in the caudate nucleus and the putamen of the GDNF-treated animals but not in the nucleus accumbens. Intraventricular administration of GDNF improved MPTP-induced disability and reversed dopamine cell loss in the substantia nigra. GDNF also diminished L-DOPA-induced dyskinesia, which may relate to its ability to partly restore nigral dopaminergic transmission or to modify the activity of striatal output pathways.

Topics: Animals; Antiparkinson Agents; Body Weight; Callithrix; Corpus Striatum; Disease Models, Animal; Dopamine Uptake Inhibitors; Dyskinesia, Drug-Induced; Enkephalins; Female; Gene Expression; Glial Cell Line-Derived Neurotrophic Factor; Levodopa; Locomotion; Male; Mazindol; MPTP Poisoning; Nerve Growth Factors; Nerve Tissue Proteins; Neuroprotective Agents; Protein Precursors; Recovery of Function; RNA, Messenger; Substantia Nigra; Tachykinins; Tritium; Tyrosine 3-Monooxygenase

Nicotine exposure modifies the expression of catecholamine and opioid neurotransmitter systems involved in attenuation of hypoxic chemosensitivity. We used in situ hybridization histochemistry to determine the effect of prenatal and early postnatal nicotine exposure on tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DbetaH), preproenkephalin (PPE), and D2-dopamine receptor mRNA levels in the rat carotid body and petrosal ganglion during postnatal development. In the carotid body, nicotine increased TH mRNA expression in animals at 0 and 3 postnatal days (both, P < 0.05 vs. control) without affecting TH mRNA levels at 6 and 15 days. At 15 postnatal days, DbetaH mRNA levels were increased in the carotid body of nicotine-exposed animals. Dopamine D2-receptor mRNA levels in the carotid body increased with postnatal age but were unaffected by nicotine exposure. PPE was not expressed in the carotid body at any of the ages studied in control or treated animals. In the petrosal ganglion, nicotine increased the number of ganglion cells expressing TH mRNA in animals at 3 days (P < 0.01 vs. control). DbetaH mRNA expression was not induced nor was PPE mRNA expression increased in the petrosal ganglion in treated animals. Prenatal nicotine exposure upregulates mRNAs involved in the synthesis of two inhibitory neuromodulators, dopamine and norepinephrine, in peripheral arterial chemoreceptors, which may contribute to abnormalities in cardiorespiratory control observed in nicotine exposed animals.

Topics: Animals; Animals, Newborn; Body Weight; Carotid Body; Catecholamines; Enkephalins; Female; Ganglia, Parasympathetic; Ganglionic Stimulants; Hemodynamics; In Situ Hybridization; Nicotine; Pregnancy; Protein Precursors; Rats; Rats, Sprague-Dawley; Receptors, Dopamine D2; Respiratory Mechanics; RNA, Messenger; Tyrosine 3-Monooxygenase; Up-Regulation

The functional interactions between the endogenous cannabinoid and opioid systems were evaluated in pre-proenkephalin-deficient mice. Antinociception induced in the tail-immersion test by acute Delta9-tetrahydrocannabinol was reduced in mutant mice, whereas no difference between genotypes was observed in the effects induced on body temperature, locomotion, or ring catalepsy. During a chronic treatment with Delta9-tetrahydrocannabinol, the development of tolerance to the analgesic responses induced by this compound was slower in mice lacking enkephalin. In addition, cannabinoid withdrawal syndrome, precipitated in Delta9-tetrahydrocannabinol-dependent mice by the injection of SR141716A, was significantly attenuated in mutant mice. These results indicate that the endogenous enkephalinergic system is involved in the antinociceptive responses of Delta9-tetrahydrocannabinol and participates in the expression of cannabinoid abstinence.

Topics: Acute Disease; Analysis of Variance; Animals; Autoradiography; Behavior, Animal; Body Temperature; Body Weight; Brain; Chronic Disease; Dronabinol; Drug Tolerance; Enkephalins; Hyperalgesia; Mice; Mice, Inbred C57BL; Mice, Knockout; Piperidines; Protein Precursors; Psychotropic Drugs; Pyrazoles; Receptors, Cannabinoid; Receptors, Drug; Rimonabant; Substance Withdrawal Syndrome

Effects of streptozotocin (STZ)-induced diabetes and insulin on opioid peptide gene expression were examined in rats. In experiment 1, three groups were administered STZ (75 mg/kg ip single injection). Two groups were killed at either 2 or 4 wk. In the third group, insulin treatment (7.0 IU/kg x 1 day for 3 wk) was initiated 1 wk after STZ injection. STZ induced hyperphagia and reduced weight gain. Insulin decreased food intake and increased body weight relative to diabetes. Proopiomelanocortin (POMC) mRNA in arcuate nucleus (Arc) and pituitary decreased in diabetes and normalized after insulin treatment. Prodynorphin (proDyn) mRNA increased in diabetes and normalized in the pituitary after insulin but not in the Arc. Diabetes did not alter proenkephalin (proEnk) expression in the Arc or pituitary, nor dynorphin A1-17 or beta-endorphin in paraventricular nucleus (PVN). alpha-Melanocyte-stimulating hormone (alpha-MSH) peptide levels were decreased in the PVN and normalized following insulin treatment. Diabetes increased Arc neuropeptide Y mRNA, and insulin suppressed this increase. In experiment 2, insulin (2.5 IU/kg sc) daily for 1 wk in normal rats increased Arc POMC mRNA, but not proDyn and proEnk mRNA. These results suggest that Arc POMC expression and PVN alpha-MSH peptide levels decrease in diabetes. Also, insulin may influence Arc and pituitary POMC activity in neurons that regulate energy metabolism.

Topics: alpha-MSH; Animals; Arcuate Nucleus of Hypothalamus; Blood Glucose; Body Weight; Diabetes Mellitus, Experimental; Eating; Energy Metabolism; Enkephalins; Gene Expression; Hypoglycemic Agents; Insulin; Leptin; Male; Melanocytes; Neuropeptide Y; Paraventricular Hypothalamic Nucleus; Pituitary Gland; Pro-Opiomelanocortin; Protein Precursors; Proteins; Rats; Rats, Sprague-Dawley; RNA, Messenger

It is established that dopamine (DA) controls the expression of preprodynorphin (PPDYN), preprotachykinin A (PPT-A) and preproenkephalin (PPE) mRNAs in striatal structures. Since cocaine, nicotine and ethanol enhance extracellular DA concentration, we have examined whether their repeated administration produced common changes in the expression of these mRNAs. Quantitative in situ hybridization histochemistry was performed in rats 2 h after a final challenge subsequent to repeated subcutaneous injections (3 X a day) of cocaine (12.5 mg/kg), nicotine (0.4 mg/kg) for 14 days and ethanol (160 mg/kg) for 7 days. In the dorsal striatum, cocaine produced simultaneous PPDYN and PPT-A mRNA increases without PPE mRNA change whereas nicotine and ethanol produced no modification. After cocaine, PPDYN mRNA was preferentially increased in striatal patch compartment. In the nucleus accumbens, the effects were more complex. In cocaine-treated rats, we measured concomitant increases of PPDYN and PPE mRNA in the rostral pole, an isolated induction of PPT-A mRNA signals in the core without any change in the two shell subregions: the cone and the ventral shell. In contrast, after nicotine and ethanol, the ventral shell was the only accumbal subregion which showed a neuropeptide mRNA alteration, nicotine leading to decreased PPDYN mRNA and ethanol to increased PPT-A mRNA contents. The neuropeptide regulation after chronic treatment with these psychostimulant drugs does not strictly conform to a general DA control scheme in the dorsal and the ventral striatum. The cocaine effects can be clearly distinguished from those of nicotine and ethanol in terms of neuropeptide regulation and striatal subregions affected.

Topics: Animals; Body Weight; Cocaine; Corpus Striatum; Drug Administration Schedule; Dynorphins; Enkephalins; Ethanol; In Situ Hybridization; Injections, Subcutaneous; Male; Nicotine; Nucleus Accumbens; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Tachykinins

We have previously reported the increase of preproenkephalin (PPE) mRNA in the caudal periaqueductal gray (PAG) of rats during morphine withdrawal. In this study, it was further evidenced that PPE mRNA in the caudal PAG was not increased by various kinds of stressor, suggesting that the increase in PPE mRNA in the caudal PAG is specific to morphine withdrawal. In order to investigate the physiological significance of the increase of PPE mRNA in the caudal PAG, we compared the time course of the increase of PPE mRNA in the caudal PAG with that of naloxone-precipitated or spontaneous morphine withdrawal signs. The increase of plasma corticosterone (PCS: 52 and 52 microg/100 ml; control group, 18 and 15 microg/100 ml) and body weight loss (-6 and -9%; control group, 0 and -1%) were observed but PPE mRNA increase was not detected 1 and 2 h after naloxone in morphine treated rats. PPE mRNA increased by 37 to 56%, while PCS elevation and body weight loss gradually diminished 4 h to 2 days after naloxone. A total of 12 h after spontaneous withdrawal, PCS was prominently increased (51 microg/100 ml; control group, 12 microg/100 ml), but body weight and PPE mRNA were not affected. One day after spontaneous withdrawal, PCS elevation (38 microg/100 ml; control group, 8 microg/100 ml) and body weight loss (-5%; control group, +3%) were observed and PPE mRNA also increased by 42%. Two to 3 days after the final morphine injection, PCS recovered to control level and body weight loss gradually disappeared, while PPE mRNA was still increased by 74 to 46%. These results suggest that PPE gene expression in the caudal PAG is stimulated in the recuperative phase of these morphine withdrawal signs.

Topics: Animals; Body Weight; Corticosterone; Enkephalins; Gene Expression Regulation; Injections, Subcutaneous; Male; Morphine; Naloxone; Periaqueductal Gray; Protein Precursors; Rats; Rats, Sprague-Dawley; Stress, Physiological; Substance Withdrawal Syndrome; Time Factors

The enkephalins are derived from a common precursor protein known as preproenkephalin (ppENK). Enkephalins appear to be one of the endogenous ligands for the opiate receptors. In the rat the ventricular myocardium contains more ppENK mRNA than any other tissue. To gain further insight into the role of cardiac enkephalins, the regional and developmental distribution of ppENK mRNA was studied by Northern blotting and in situ hybridization. In the early postnatal period, ppENK mRNA is low in atrial and ventricular myocardium. With maturation, ppENK expression increases threefold in left and right ventricular tissue, but not in the atria or cardiac conductive system. Interestingly, ppENK mRNA levels are four times higher in the left than in the right chamber. Thus, to our knowledge, ppENK is the only gene exhibiting marked differences in expression between the adult right and left ventricle. Given the left-side preference of ppENK expression, the possibility is raised that the left ventricle is an endocrine organ that supplies the body with enkephalins.

Topics: Aging; Animals; Animals, Newborn; Blotting, Northern; Body Weight; Enkephalins; Female; Gene Expression Regulation, Developmental; Heart; Heart Ventricles; In Situ Hybridization; Male; Myocardium; Organ Size; Protein Precursors; Rats; Rats, Wistar; RNA, Messenger; Transcription, Genetic

Although opioid administration induces food intake, the relationship between endogenous opioid synthesis and food consumption is unclear. Two studies examined the effects of food restriction and deprivation on opioid mRNA levels in the arcuate nucleus (ARC) of the rat. Body weight significantly decreased following food restriction and deprivation (P < 0.0001). In experiment 1, food restriction of 10,20,30, and 40% (g) of ad libitum intake for 14 days decreased proDynorphin (proDyn), proEnkephalin (proEnk), and proOpiomelanocortin (POMC) mRNA levels in a linear fashion relative to changes in body weight (r = 0.398, P = 0.0011; r = 0.455, P = 0.0028; r = 0.292, P = 0.0642, respectively). In experiment 2, 48 h deprivation significantly decreased mRNA levels of proDyn and POMC by 23.7% (P < 0.05) and 45.6% (P < 0.01), respectively, whereas 24 h food deprivation decreased POMC mRNA by 43.% (P < 0.01). proEnk mRNA was not affected by 24- or 48-h food deprivation. Restricting food intake suppressed mRNA levels of proDyn, proEnk, and POMC by 29.7, 22.3, and 44.4%, respectively, in 20% restricted rats and by 35.5, 26.8, and 45.6%, respectively, in 40%restricted rats (P < 0.01). It appears that ARC mRNA levels of proDyn, proEnk, and POMC are directly related to the amount of food consumed and/or changes in body weight in food-restricted and food-deprived rats.

Topics: Animals; Arcuate Nucleus of Hypothalamus; Body Weight; Enkephalins; Food Deprivation; Male; Pro-Opiomelanocortin; Protein Precursors; Rats; Rats, Sprague-Dawley; RNA, Messenger; Time Factors

It has been reported that perinatal exposure to opiates affects mRNA synthesis, body growth and brain development in mammals, including humans. We have observed that morphine administration in drinking water during the perinatal period alters peptide development in the striatum of the rat. There is a marked increase in substance P and met-enkephalin content, the latter is maintained even at 30 days postnatally. The transient increase or earlier maturation of substance P content is correlated by a more precocious axon terminal organization as revealed by immunocytochemical staining. The increased metenkephalin content is correlated by a higher abundance of preproenkephalin A mRNA and this correlation is particularly evident at 15 days postnatally. At earlier times both northern blotting and in situ hybridization techniques fail to show any significant difference between control and morphine exposed rats, likely because the peptide content is not very different in the two groups or at least the gap is not as wide as at later times.

Topics: Animals; Blotting, Northern; Body Weight; Corpus Striatum; Endorphins; Enkephalin, Methionine; Enkephalins; Female; Growth; Immunohistochemistry; In Situ Hybridization; Morphine; Naloxone; Naltrexone; Protein Precursors; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Substance P

The regulation of prodynorphin gene expression by glucocorticoids in the hippocampus was examined in rats that were adrenalectomized (ADX) either 7, 30, 60 and 90 days prior to sacrifice. Peptide levels in the hippocampus of ADX rats were determined by radioimmunoassay and immunocytochemistry. Prodynorphin (PDYN) mRNA was measured by Northern blot analysis and in situ hybridization. A time-dependent decrease in dynorphin A(1-8)(DYN) levels in the hippocampus (18% at 7 days; 44% at 30 days; 58% at 60 days) of ADX rats was found, which was accompanied by a comparable decrease in the abundance of PDYN mRNA. An in situ hybridization analysis revealed that both the number of positively hybridized cells and the number of silver grains per cell were decreased in the dentate gyrus after ADX. The administration of dexamethasone after surgery reversed the peptide and mRNA attenuation induced by ADX. ADX had no effect on the expression of proenkephalin mRNA or [Met5]-enkephalin immunoreactivity in the hippocampus. Examination of thionin-counterstained tissue showed that the dentate granule cell layer was intact. The decrement of DYN expression in this system is proposed to have resulted from the removal of glucocorticoid input and not dentate granule cell loss. This study provides the strong evidence for a differential susceptibility of these two opioid peptides in the hippocampus to the removal of glucocorticoids. In addition, these data provide support for a potentially selective, glucocorticoid-permissive component in PDYN gene expression.

Topics: Adrenal Glands; Adrenalectomy; Animals; Body Weight; Corticosterone; Dexamethasone; Enkephalins; Gene Expression Regulation; Glucocorticoids; Hippocampus; Male; Neuropeptides; Protein Precursors; Random Allocation; Rats; Rats, Inbred F344; RNA, Messenger

The influence of chronic arthritic pain upon the levels of mRNA encoding prodynorphin (mRNADYN) in the spinal cord of rats was evaluated by use of the RNA blot technique. Rats were rendered arthritic by inoculation of the tail-base with a suspension of Mycobacterium butyricum. Three weeks post inoculation, levels of mRNADYN revealed a pronounced alteration in arthritic rats by a factor of greater than or equal to 2.5 as compared to control animals. This rise was specific in that there was no change in total RNA content. These data indicate that the biosynthetic activity of the dynorphin system is facilitated under chronic pain. Together with our previous biochemical and behavioural data, a functional role of this system in the response to chronic pain is suggested.

Topics: Animals; Arthritis; Arthritis, Experimental; Body Weight; Enkephalins; Gene Expression Regulation; Male; Nucleic Acid Hybridization; Organ Size; Pain; Protein Precursors; Rats; Rats, Inbred Strains; RNA; RNA, Messenger; Spinal Cord