Somatostatin decreases somatostatin messenger ribonucleic acid levels in the rat periventricular nucleus

Growth hormone (GH) secretion from the pituitary is known to be under the dual control of GH-releasing factor (GRF) and somatostatin (SRIF). Hypothalamic SRIF, the major inhibitor of pituitary growth hormone secretion, inhibits its own release by a negative ultrashort-loop feedback mechanism. However, it is not known whether this negative regulation is mediated by inhibition of SRIF mRNA production. GRF may also inhibit its own release, thereby modifying pituitary GH secretion, possibly through an ultrashort-loop feedback mechanism. Thus, SRIF production and GRF release are both regulated by SRIF. Periventricular nucleus (PeN) and mediobasal hypothalamus (MBH) from adult male rats were incubated for 6 h in Waymouth's medium with either SRIF or the SRIF agonist analog RC 160 (10(-9) to 10(-6) M). Levels of SRIF mRNA were determined by an S1 nuclease protection assay using a 32[P]-labeled rat SRIF riboprobe. SRIF (10(-7) M) and RC 160 (10(-8), 10(-7) M) significantly (p< or =0.01) decreased SRIF mRNA levels in the PeN. The levels of SRIF mRNA in the MBH were not modified by either SRIF or RC 160. SRIF (10(-7) and 10(-6) M) significantly (p < or = 0.01 and p < or = 0.001, respectively) inhibited the release of GRF at 30 min in the MBH. Likewise, the release of GRF was slightly decreased by 10(-7) M RC 160, and significantly inhibited by 10(-6) M (p < or = 0.001) at 30 min. At 6 h, the levels of GRF were significantly reduced by 10(-7) M SRIF (p < or = 0.05) and by RC 160 (10(-7), 10(-6) M; p < or = 0.001 and p < or = 0.05, respectively). In contrast with these results, the SRIF analog was unable to alter SRIF release at 30 min. At 6 h incubation, RC 160 (10(-7) M) significantly (p < or = 0.001) reduced SRIF release from MBH fragments. These results demonstrate that SRIF and a SRIF analog decrease SRIF mRNA levels in the PeN and inhibit the release of SRIF from the nerve terminals of the MBH. Thus, SRIF appears to regulate its own gene expression by negative ultrashort-loop feedback. Therefore, when SRIF is secreted from these neurons in response to GRF, it down-regulates the preceding stimulatory input as well as its own secretion.     

Regulation of oxytocin receptor messenger ribonucleic acid in the ventromedial hypothalamus by testosterone and its metabolites

Oxytocin receptor (OR) binding in the ventromedial hypothalamus (VMH) is regulated by testosterone (T) and its metabolites, estrogen (E2) and dihydrotestosterone (DHT). Previous studies have reported that OR binding increases in the VMH in castrated male rats when they are replaced with T or E2 compared to that in vehicle-treated animals. DHT alone had no effect on OR binding, but when given in combination with E2 appeared to have a synergistic effect. This study was designed to determine whether these effects of steroid hormones on OR binding in the VMH are associated with changes in OR messenger RNA (mRNA) expression. Male rats were castrated or sham operated and given T propionate (TP), E2 benzoate (EB), DHT plus EB, or an oil vehicle. OR mRNA was assessed using a rat complementary RNA OR probe and in situ hybridization techniques. OR binding to tissue slices was quantified autoradiographically using an OR antagonist, [125I]d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)] ornithine vasotocin. These experiments showed that TP and EB increased both OR mRNA and OR binding in the VMH significantly above levels in vehicle-treated animals. However, animals given both EB and DHT exhibited significantly lower OR mRNA expression and OR binding in the VMH compared to those in animals treated with TP or EB alone. These data indicate that increases in VMH OR binding in response to gonadal steroids are accompanied by changes at the mRNA level that correspond well in magnitude and direction with those in the OR-binding sites.     

Estrogen-induced alteration of mu-opioid receptor immunoreactivity in the medial preoptic nucleus and medial amygdala

The mu-opioid receptor (mu-OR), like most G-protein-coupled receptors, is rapidly internalized after agonist binding. Although opioid peptides induce internalization in vivo, there are no studies that demonstrate mu-OR internalization in response to natural stimuli. In this study, we used laser-scanning microscopy to demonstrate that estrogen treatment induces the translocation of mu-OR immunoreactivity (mu-ORi) from the membrane to an internal location in steroid-sensitive cell groups of the limbic system and hypothalamus. Estrogen-induced internalization was prevented by the opioid antagonist naltrexone, suggesting that translocation was largely dependent on release of endogenous agonists. Estrogen treatment also altered the pattern of mu-ORi at the bright-field light microscopic level. In the absence of stimulation, the majority of immunoreactivity is diffuse, with few definable mu-OR+ cell bodies or processes. After stimulation, the density of distinct processes filled with mu-ORi was significantly increased. We interpreted the increase in the number of mu-OR+ processes as indicating increased levels of internalization. Using this increase in the density of mu-OR+ fibers, we showed that treatment of ovariectomized rats with estradiol benzoate induced a rapid and reversible increase in the number of fibers. Significant internalization was noted within 30 min and lasted for >24 hr after estrogen treatment in the medial preoptic nucleus, the principal part of the bed nucleus, and the posterodorsal medial amygdala. Naltrexone prevented the increase of mu-OR+ processes. These data imply that estrogen treatment stimulates the release of endogenous opioids that activate mu-OR in the limbic system and hypothalamus providing a "neurochemical signature" of steroid activation of these circuits.     

Activation of the human estrogen receptor by estrogenic and antiestrogenic compounds in Saccharomyces cerevisiae: a positive selection system

OBJECTIVE: To develop a slow-release carboplatin formulation for intratumoral administration to cats. DESIGN: Preliminary study to analyze pharmacokinetic effects of purified sesame oil in the carboplatin formulation for intratumoral administration, and a second study to evaluate the efficacy and toxicosis of intratumoral administration of carboplatin in purified sesame oil. ANIMALS: 23 cats with squamous cell carcinomas of the nasal plane. PROCEDURE: Eight cats with advanced-stage tumors were submitted to intratumoral administration of 100 mg of carboplatin/m2 of body surface area, with or without purified sesame oil, using a two-period, cross-over design. Fifteen additional cats were treated by intratumoral administration of carboplatin in purified sesame oil. Four weekly intratumoral chemotherapy injections of carboplatin in purified sesame oil at a dosage of 1.5 mg/cm3 of tissue were given. RESULTS: Purified sesame oil in the formulation significantly reduced systemic exposure to carboplatin and drug leakage from the sites of injection. Cumulative effects of repeated intratumoral administrations on plasma concentrations of carboplatin were not observed. Systemic toxicosis was not observed, and local toxicosis was minimal. Healing of ulcerated lesions was not compromised. Rates of complete clinical tumor clearance and complete response were 67 and 73.3%, respectively. Product-limit estimates of mean progression-free survival times was 16 +/- 3.3 months. The 1-year progression-free survival rate was 55.1 +/- 13%. Local recurrence was observed in 7 cats; 4 had marginal tumor recurrence, and 3 had in-field and marginal tumor recurrence. CONCLUSIONS: Intratumoral carboplatin chemotherapy is safe and effective for cats with squamous cell carcinoma of the nasal plane. Future studies to improve treatment efficacy could include evaluation of increased dose-intensity as well as combination of this modality with radiotherapy. CLINICAL RELEVANCE: Intratumoral administration of carboplatin in a water-sesame-oil emulsion was found to be a practical and effective new treatment for facial squamous cell carcinomas in cats.     

Localization and differential expression of adenylyl cyclase messenger ribonucleic acids in rat adrenal gland determined by in situ hybridization

The expression of adenylyl cyclases (ACs) in the adult rat adrenal gland was examined. In situ hybridization revealed specific patterns of AC messenger RNA (mRNA) distribution. AC1 was limited exclusively to the adrenal medulla. AC5 and AC6 were mainly expressed in the adrenal medulla, with a weak expression in the zona glomerulosa. AC9 was found in all the three regions of the adrenal cortex but not in the adrenal medulla. All these ACs were detected on postnatal day 1 (PN1), and their pattern of expression was unchanged on PN7, PN21, and PN90 (adult). We analyzed the response of these ACs to various physiological conditions known to affect the synthesis of aldosterone and corticosterone in the adrenal cortex. Our study demonstrates a specific increase of AC6 but not AC5 mRNA in the zona glomerulosa of rats given a low sodium diet. AC9 mRNA was increased in all the three cortical zones of rats treated with ACTH. We suggest that AC6 and AC9 play important roles in different pathways associated with the regulation of aldosterone and corticosteroid production.     

Ontogeny of estrogen receptor messenger ribonucleic acid expression in the postnatal rat uterus

During the first 2 wk of postnatal life, the rodent uterus undergoes a period of marked growth and differentiation. To further examine the role of the estrogen receptor (ER) in the mediation of uterine development, we analyzed the ontogeny of ER mRNA expression in the postnatal rat uterus using in situ hybridization. ER mRNA was present in the uterine stroma on the day of birth and progressively increased in abundance during the first 2 wk of postnatal life. In contrast, ER mRNA was not detectable in the luminal epithelium at birth and did not become abundant in this region until postnatal day (P) 7. ER mRNA abundance increased in the luminal epithelium and in the invaginating and fully formed glandular epithelium during the second week of life. At P21 ER mRNA was more abundant in the glandular epithelium than in any other uterine cell type. These results are consistent with, and extend the findings of, previous studies using uterine homogenate binding assays and immunohistochemistry to define ER ontogeny in rodents. Delineation of the temporal and cell-type specific pattern of ER mRNA ontogeny in the postnatal rat uterus furthers our understanding of the molecular basis of both endogenous and exogenous estrogen effects on uterine growth and development.     

Up-regulation of oxytocin receptor messenger ribonucleic acid and protein by estradiol in the cervix of ovariectomized rat

Oxytocin receptor (OTR) regulation has been extensively studied in uterine myometrium and endometrium. However, studies in the cervix are limited. The present studies utilized in situ hybridization and immunocytochemistry to localize OTR mRNA and protein distribution in cervices of nonpregnant ovariectomized (OVX) rats and examined the effect of combined and independent treatments with estradiol and progesterone on cervical OTR. Thirteen nonpregnant rats were bilaterally OVX under general anesthesia. At least 7 days later, the rats were exposed to one of four different treatments 24 h prior to necropsy: 1) estradiol (50 microg, n = 4); 2) progesterone (10 mg, n = 3); 3) both estradiol (50 microg) and progesterone (10 mg) (n = 3); 4) corn oil vehicle (n = 3). After 24-h estradiol treatment, OTR mRNA increased significantly (p < 0.05) in smooth muscle cells of the rat cervix as a result of increased copy numbers of OTR mRNA per cell as well as an increased population of OTR mRNA-positive cells. Progesterone alone had no effect on OTR mRNA expression; however, progesterone combined with estradiol significantly inhibited the up-regulation of OTR mRNA by estradiol alone. The increase of OTR mRNA in cervical epithelial cells was minimal in all situations. Intensity of cervical OTR immunostaining in both the epithelial cells and cervical smooth muscle cells was also elevated after estradiol treatment. The anti-rat OTR antiserum used for immunocytochemistry was validated by Western blot analysis. In conclusion, OTR and OTR mRNA were localized in smooth muscle cells and in epithelial cells of rat cervix. Estradiol-dependent activation of OTR gene expression and active OTR synthesis in smooth muscle cells account for the increased OTR level in rat cervix in vivo, in which progesterone acted as an antagonist of estradiol on OTR gene expression.     

Regulation of messenger ribonucleic acid for corticotropin releasing hormone receptor in the pituitary during stress

The mechanism regulating pituitary CRH receptors during stress was studied by analysis of the changes in CRH receptor messenger RNA (mRNA) and CRH binding after acute and repeated stress and CRH and vasopressin (VP) administration in intact and adrenalectomized rats. Acute stress caused time- and stress type-dependent changes in pituitary CRH receptor expression. In situ hybridization studies showed biphasic changes in CRH receptor mRNA after immobilization stress for 1 h and decreases by 2 h (P < 0.01). Increases (P < 0.01) were seen 4 and 8 h after the initiation of the stress, and a return to near basal levels by 12 and 18 h. A different pattern, with a decrease by 4 h (P < 0.01) and levels similar to controls after 12 and 18 h, was observed after a single ip injection of hypertonic saline (1.5 M NaCl). Binding autoradiography showed significant increases in pituitary CRH binding 4, 10, and 12 h after immobilization stress, but significant decreases 4, 12, and 18 h after ip hypertonic saline. In contrast, repeated immobilization or ip hypertonic saline for 8 or 14 days increased pituitary CRH receptor mRNA, and CRH binding was decreased. To determine the role of hypothalamic CRH and VP on these stress-induced changes, rats were injected for 14 days with CRH, VP, or their combination at doses mimicking stress levels in pituitary portal circulation (1 microgram/day sc). Repeated injection of CRH or VP increased CRH receptor mRNA and CRH binding (P < 0.05). CRH receptor mRNA levels further increased after combined administration of CRH and VP (P < 0.01), but CRH binding showed a tendency to decrease. The role of glucocorticoids on CRH receptor regulation was studied by analysis of the effects of stress on CRH receptor mRNA and CRH binding in adrenalectomized (ADX) rats with and without corticosterone replacement in the drinking water. Although in 6-day ADX rats pituitary CRH receptor mRNA levels were markedly reduced after acute immobilization, glucocorticoid replacement restored the stimulatory effect of stress to levels observed in intact rats. Similarly, a single sc injection of CRH (1 microgram) decreased CRH receptor mRNA in ADX rats but not in glucocorticoid-replaced ADX rats. CRH binding showed the expected decrease after ADX and was unchanged after stress or CRH injection. The increased pituitary CRH receptor mRNA after stress suggests that stress-induced CRH receptor down-regulation is due to increased receptor occupancy and internalization rather than to a decrease in receptor synthesis. The data suggest that increased hypothalamic secretion of CRH and VP mediates the delayed up-regulatory effect of stress on CRH receptor mRNA, and that resting levels of glucocorticoids are required for this effect. In addition, increased VP levels are permissive for the down-regulation of CRH binding induced by chronic pituitary exposure to stress levels of CRH.     

Effect of fasting on insulin receptor-related receptor messenger ribonucleic acid in rat kidney

The insulin receptor-related receptor (IRR), a member of the insulin receptor tyrosine kinase family, has structural homology to the insulin receptor (IR) and the IGF-I receptor (IGF-IR). The ligand, gene regulation and biological function of the IRR are not known. Because mRNAs for both the IR and IGF-IR are increased by nutrient restriction, we used RNase protection assays to assess the effects of fasting 48 h on IRR mRNA in kidneys of rats. We compared the changes in IRR with those in IR and IGF-IR mRNAs. We observed a significant increase in steady state levels of IRR (ratio of IRR mRNA to beta-actin in fed P<0.01), suggesting that the ligand for IRR also might be regulated by nutrients.     

Expression of acetylcholinesterase messenger RNA in human brain: an in situ hybridization study

The distribution of messenger RNA coding for acetylcholinesterase was studied in human post mortem brain and rhesus monkey by in situ hybridization histochemistry and compared to the distribution of acetylcholinesterase activity. Acetylcholinesterase messenger RNA had--similar to acetylcholinesterase enzymatic activity--a widespread distribution in human bain. Acetylcholinesterase messenger RNA positive cells corresponded to perikarya rich in acetylcholinesterase activity in most but not all regions. Examples for mismatches included the inferior olive and human cerebellar cortex. The presence of hybridization signals in cerebral cortex and an enrichment in layer III and V of most isocortical areas confirmed that perikaryal acetylcholinesterase in cerebral cortex is of postsynaptic origin and not derived from cholinergic projections. In striatum the expression of high levels of acetylcholinesterase messenger RNA was restricted to a small population of large striatal neurons. In addition, low levels of expression were found in most medium sized striatal neurons. Cholinergic neurons tended to express high levels of acetylcholinesterase messenger RNA whereas in cholinoceptive neurons the levels were moderate to low. However, some noncholinergic neurons like dopaminergic cells in substantia nigra, noradrenergic cells in locus coeruleus, serotoninergic cells in raphé dorsalis, GABAergic cells in thalamic reticular nucleus, granular cells in cerebellar cortex and pontine relay neurons expressed levels comparable to cholinergic neurons in basal forebrain. It is suggested that neurons expressing high levels of acetylcholinesterase messenger RNA may synthesize acetylcholinesterase for axonal transport whereas neurons with an expression of acetylcholinesterase confined to somatodendritic regions tend to contain lower levels of acetylcholinesterase messenger RNA.     

Currents evoked by GABA and glycine in acutely dissociated neurons from the rat medial preoptic nucleus

The responses of acutely dissociated medial preoptic neurons to application of GABA, and glycine were studied using the perforated-patch whole-cell recording technique under voltage-clamp conditions. GABA, at a concentration of 1 mM, evoked outward currents in all cells (n = 33) when studied at potentials positive to -80 mV. The I-V relation was roughly linear. The currents evoked by GABA were partially blocked by 25-75 microM picrotoxin and were also partially or completely blocked by 100-200 microM bicuculline. Glycine, at a concentration of 1 mM, did also evoke outward currents in all cells (n = 12) when studied at potentials positive to -75 mV. The I-V relation was roughly linear. The currents evoked by glycine were largely blocked by 1 microM strychnine. In conclusion, the present work demonstrates that neurons from the medial preoptic nucleus of rat directly respond to the inhibitory transmitters GABA and glycine with currents that can be attributed to GABAA receptors and glycine receptors respectively.     

Ontogeny of region-specific sex differences in androgen receptor messenger ribonucleic acid expression in the rat forebrain

Testosterone and its metabolites are the principal gonadal hormones responsible for sexual differentiation of the brain. However, the relative roles of the androgen receptor (AR) vs. the estrogen receptor in specific aspects of this process remain unclear due to the intracellular metabolism of testosterone to active androgenic and estrogenic compounds. In this study, we used an 35S-labeled riboprobe and in situ hybridization to analyze steady state, relative levels of AR messenger RNA (mRNA) expression in the developing bed nucleus of the stria terminalis, medial preoptic area, and lateral septum, as well as the ventromedial and arcuate nuclei of the hypothalamus. Each area was examined on embryonic day 20 and postnatal days 0, 4, 10, and 20 to produce a developmental profile of AR mRNA expression. AR mRNA hybridization was present on embryonic day 20 in all areas analyzed. In addition, AR mRNA expression increased throughout the perinatal period in all areas examined in both males and females. However, between postnatal days 4 and 10, sharp increases in AR mRNA expression in the principal portion of the bed nucleus of the stria terminalis and the medial preoptic area occurred in the male that were not paralleled in the female. Subsequently, males exhibited higher levels of AR mRNA than females in these areas by postnatal day 10. There was no sex difference in AR mRNA content in the lateral septum, ventromedial nucleus, or arcuate nucleus at any age. These results suggest that sex differences in AR mRNA expression during development may lead to an early sex difference in sensitivity to the potential masculinizing effects of androgen.     

Expression of somatotropin receptor messenger ribonucleic acid in bovine tissues

The somatotropin receptor mRNA is controlled by at least two different gene promoters that generate two variants with different exon 1 sequences (1A and 1B). The location of 1A and 1B somatotropin receptor mRNA within cattle tissues and, hence, the tissue specificity of the 1A and 1B promoters are unknown. In addition, the cDNA sequence of the 1B somatotropin receptor has not been determined. Our objective, therefore, was to sequence a cDNA for the 1B somatotropin receptor and to analyze bovine tissues for expression of 1A and 1B somatotropin receptor mRNA. Twenty adult tissues and six fetal tissues were collected at slaughter from each of four cows and two fetuses. Messenger RNA was analyzed using ribonuclease protection assays. The adult liver expressed both 1A and 1B mRNA. All other adult tissues expressed 1B mRNA but not 1A mRNA. The greatest amount of 1B mRNA was detected in liver and adipose (abdominal and subcutaneous) tissues. Other tissues had approximately one-half to one-tenth of the amount of 1B mRNA in the liver or adipose tissue. Fetal tissues (including fetal liver) expressed 1B mRNA and not 1A mRNA. Based on cDNA sequencing, the protein encoded by the 1A and 1B mRNA was nearly identical. We concluded that 1A somatotropin receptor mRNA is specific to adult bovine liver. Other adult and fetal bovine tissues expressed 1B somatotropin receptor mRNA with a predicted protein sequence that was similar to the 1A somatotropin receptor.     

Corticotropin releasing factor receptor type II (CRF2) messenger ribonucleic acid levels in the hypothalamic ventromedial nucleus of the infant rat are reduced by maternal deprivation

The stress neurohormone corticotropin releasing factor (CRF) activates at least two receptor types. Expression of corticotropin releasing factor receptor type II (CRF2) has been demonstrated in the hypothalamic ventromedial nucleus (VMH) of the adult and developing rat, but the physiological functions of VMH-CRF2 have not been elucidated. The VMH has been documented as an important participant in the regulation of food intake and its interactions with the hypothalamic-pituitary-adrenal axis and circadian rhythms. Regulation of VMH-CRF2 may thus play a role in the interplay of physiological alterations in metabolic state with the neuroendocrine and anorexic effects of CRF. This study determined the regulation of CRF2-mRNA expression in infant rats by the physiological consequences of maternal deprivation, i.e., fasting and stress. Using in situ hybridization, maternally deprived pups had an average 62% reduction of VMH-CRF2-mRNA levels compared with stress-free controls. Maternal deprivation also resulted in elevated plasma corticosterone levels (3.8 +/- 0.3 vs. 1.3 +/- 0.1 microg/dl) and an average 5.7% body weight loss. This study demonstrates that maternal deprivation, via fasting and HPA activation, leads to a dramatic decrease of CRF2-mRNA levels in the VMH. These results are consistent with a role for CRF2 activation in mediating some of the complex interactions of CRF (or urocortin) with regulation of food intake in the developing rat.     

Neurotrophins and their receptors in the adult hypo- and hyperthyroid rat after kainic acid injection: an in situ hybridization study

Thyroid hormone plays a key role in trophic events during development of the central nervous system. In spite of neurological and psychiatric symptoms associated with adult hypothyroidism, the role of thyroid hormone in mature brain function is less clear. In this paper we investigated the effect of thyroid status on kainic acid-induced up-regulation of mRNAs for members of the nerve growth factor family and related receptors in adult male rats by means of in situ hybridization. We found that in hypothyroid rats there is a dramatic attenuation of the kainic acid-induced up-regulation of mRNA levels for nerve growth factor, brain-derived neurotrophic factor and tyrosine kinase trkB in euthyroid rats. A trend to reduced c-fos mRNA up-regulation, which did not reach significance, was also found, whereas the increase in c-jun mRNA after kainic acid was similar in eu-, hypo- and hyperthyroid rats. These data indicate a severe impairment of the regulation of neurotrophin synthesis after excitotoxin administration in the hippocampus during adult hypothyroidism. Possible roles of thyroid hormone in molecular, biochemical and metabolic mechanisms of this defect are discussed.     

Induction of macrophage migration inhibitory factor messenger ribonucleic acid in rat forebrain by reperfusion

To evaluate the impact of uremia and associated caloric restriction on physiologically pulsatile growth hormone (GH) release, we used deconvolution analysis of spontaneous plasma GH profiles in 5/6-nephrectomized male rats (NX, N = 9). Three different normal renal function sham-operated groups were used: rats fed a normal diet ad libitum (SAL, N = 9); NX pair-fed rats (SPF, N = 6); NX rats pair-fed for protein ingestion but calorically supplemented up to the energy intake of SAL (SPF+, N = 8). Severe renal failure was confirmed by much higher (P < 0.001) BUN in NX than sham groups. NX rats were growth retarded as shown by reduced (P < 0.01) weight and length gains as compared with sham animals. Deconvolution analysis (mean +/- SEM) of plasma samples obtained every 10 minutes over 6 hours, and 14 to 16 days after second stage nephrectomy showed that NX rats had a longer GH t(1/2) (17.0 +/- 1.8 vs. 11.6 +/- 0.8 min), less GH mass secreted per burst (48 +/- 15 vs. 95 +/- 16 ng/ml/pulse), lower secretory pulse amplitude (1.9 +/- 0.5 vs. 5.8 +/- 0.9 ng/ml/min), and a reduced total GH secretion (240 +/- 69 vs. 400 +/- 56 ng/ml/6 hr) than SAL rats. Corresponding data were not significantly different between NX and SPF, or between SAL and SPF+ groups. In summary, stunted rats with chronic renal failure exhibit a prolonged GH t(1/2) and suppression of GH secretory pattern burst mass. Control data from rats with normal renal function suggest that the amplitude-specific depression of GH secretion may be attributed, at least in part, to chronic renal failure-associated calorie deficiency.     

Rapid stress-induced elevations in corticotropin-releasing hormone mRNA in rat central amygdala nucleus and hypothalamic paraventricular nucleus: an in situ hybridization analysis

High densities of nerve cells containing corticotropin-releasing hormone (CRH) are located in the central nucleus of the amygdala (CeA) and paraventricular nucleus (PVN) of the hypothalamus. These brain regions play an important role in activating autonomic, behavioral, and endocrine responses to stress. This study was conducted to provide needed information concerning the acute effects of stress on CeA and PVN CRH mRNA expression. Rats were exposed to restraint stress for 1 h and brains collected after a 1-h post-stress interval. CRH mRNA expression occurring in the CeA and PVN was examined using in situ hybridization techniques. Densitometric analysis revealed that acute restraint stress produced significant increases in CRH mRNA levels in the PVN and in the rostral CeA region. In addition, the area in the rostral CeA encompassing high CRH mRNA signals increased significantly after stress. Results provide clear evidence that CRH neurons in the CeA and PVN exhibit rapid increases in CRH mRNA expression after exposure to stress.