Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of LHRH intracerebrally infused on acquisition of conditioned avoidance responses (CARs) and spontaneous motility were studied in adult male rats. The results were the following: 1) LHRH (1 and 2.5 micrograms/rat) administered through a cannula stereotaxically implanted into the lateral ventricle induced an impairment in the acquisition of CARs along with an increase in global motility, rearing, head shaking and grooming behavior; 2) LHRH 1 microgram/rat injected into the hippocampus or nucleus accumbens induced also an impairment in acquisition which is evident 15 min after treatment. In contrast, intrastriatal injection induced an immediate disruption of this behavior; and 3) there is a good dose-response relationship for intrastriatal LHRH between 7.8 and 62.5 ng/rat. The results suggest that the estriatum could be the locus of the LHRH-induced inhibition of CARs. Then the possibility of an involvement of the dopamine nigrostriatal system is discussed.
 ...
PMID:Behavioral effects of intracerebral administration of luteinizing hormone releasing hormone (LHRH) in rats. 187 Nov 86

The characteristics of the steroidogenic response of reaggregated rat interstitial cells were examined in a perifusion system. Interstitial cells were isolated from 19-day-old rat testes by digestion with collagenase. The cells were cultured for 3 days as monolayers and were resuspended by brief treatment with trypsin. Constant gyratory shaking of the dispersed cells resulted in the formation of round and compact aggregates of 70-140 microns. The functional characteristics of these aggregates were examined by studying the output of cAMP, C19 steroids (testosterone and androstenedione), and C21 steroids (progesterone, 17 alpha-hydroxyprogesterone, 20 alpha-hydroxypregn-4-en-3-one) in a perfusion system. It is demonstrated that reaggregated interstitial cells maintain their responsiveness to LH, LHRH, and Leydig cell stimulatory factor(s) produced by Sertoli cells for at least 12 days. When exposed to low concentrations of LH (1 ng/ml), either in a continuous or in a pulsatile fashion, perifused aggregates maintain a constant output of steroids for more than 20 h. Under these conditions, LH-dependent differentiation of the steroidogenic machinery can be observed in vitro. In fact, although the sum of the measured steroids remains constant, C21 steroids progressively decrease whereas C19 steroid output increases during perifusion. When perifused with high concentrations of LH (10 ng/ml), desensitization becomes the predominant phenomenon. It is demonstrated that the steroid output of reaggregated interstitial cells considerably exceeds that of similarly treated cells maintained as monolayers. Moreover, perifusion of aggregates results in a 6-fold increase in steroid output as compared to static incubation and in a selective increase in androgen output. It is concluded that prepubertal interstitial cells allowed to reaggregate in suspension culture form functional multicellular structures. Perifusion of these aggregates is a useful tool in the study of the dynamics of the regulation of steroidogenesis.
 ...
PMID:The dynamics of steroid and adenosine 3',5'-cyclic monophosphate output in perifused interstitial cell aggregates derived from prepubertal rat testes. 301 35

The influence of L-DOPA on the behavioral effects of LHRH was studied in male rats. Subcutaneous administration of LHRH (100 micrograms/kg) caused a significant disruption in the acquisition of a conditioned avoidance response (CAR) and a significant increase in head shaking behavior (HSB). Pretreatment with this hormone antagonized the stimulatory action of amphetamine (1 mg/kg, IP) in acquisition of CARs, spontaneous motor activity (SMA) and rearing behavior (RB). L-DOPA (100 mg/kg, IP), administered after LHRH, stimulated SMA, RB and HSB. In addition L-DOPA antagonized the effect of LHRH on acquisition of CARs and counteracted the antagonism between LHRH and amphetamine in acquisition of CARs and SMA. These findings indicate that LHRH could exert its behavioral effects through an inhibitory action upon brain catecholamine synthesis. The suppression of CARs may be the response to DA antagonism and the interaction with amphetamine could be mediated by an inhibition of both DA and NE activities. The possibility of an interaction between LHRH and central serotonin mechanisms is also discussed.
 ...
PMID:Pharmacological evidence of catecholaminergic involvement in the behavioral effects of luteinizing hormone releasing hormone in rats. 351 86

The present study was carried out to characterize the spontaneous release of LH and FSH from the pituitary gland of infant rats in an in vitro system. In addition, the responsiveness of their pituitary glands to synthetic LHRH in vitro was examined. Wistar-Imamichi male and female rats, aged between 1 and 21 days and androgenized female rats at 7 and 21 days of age were used. One-day-old female rats were androgenized by a subcutaneous injection of 1 mg of testosterone propionate. Animals were killed by decapitation, trunk blood was collected, and the pituitary gland was dissected free and weighed. Pituitaries were placed in 9 ml-test tube with 2 ml Krebs-Henseleit solution and incubation was carried out in a shaking incubator for 6 hours at 37 degrees C under the gassing of 5% CO2 and 95% O2. After preincubation for 15 min, medium was replaced with 2 ml fresh medium and LH and FSH concentrations released during the first 3 hr-incubation period were assessed as for the spontaneous release and the second 3 hr-incubation period assessed for the response to LHRH (10(-6)M) stimulation. In an experiment, time course changes of the spontaneous release of LH and FSH were studied using 7-day-old rat pituitaries. An aliquot of 0.5 ml of medium was taken at 30, 60, 120 and 180 min during the incubation. Gonadotropin contents in the pituitaries were determined by adding the residue in the pituitary gland and the amounts released into medium. Spontaneous release of LH and FSH increased with age in both male and female rats, and the released amounts of LH as well as FSH in female rats tended to be higher than those in males at 1, 3, 7 and 21 days of age examined. But significant sex differences in the spontaneous release of LH and FSH were only seen at 21-day-old; Spontaneous release of LH in female rats was 7 times higher than that in age-matched males. Serum LH and FSH concentrations in female rats were significantly higher than those in males at all ages examined, except the LH level at 1-day-old. In contrast to LH, age and sex differences in the magnitude of the spontaneous release of FSH from the pituitary paralleled with the age and sex differences in serum FSH concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:[Sex and age differences in the spontaneous release of gonadotropins from immature rat pituitary glands in vitro]. 642 31

Suspensions of isolated rat pituitary cells and gonadotroph- or lactotroph/somatotroph-enriched subpopulations obtained by unit gravity sedimentation were allowed to aggregate by constant gyrotory shaking, yielding aggregates of 100-150 micrometers. Within a few days, the aggregated pituitary cells became organized in a tissue-like configuration. There was no proliferation of mesenchymal cells. Glandular cells had a round to oval shape and formed specialized cell junctions. Areas of close apposition alternated with more dilated intercellular spaces. The different pituitary cell types retained their characteristic ultrastructural features and secretory granules, typical of the various cell types. Functional characteristics could be accurately studied in a superfusion system. LH, FSH, and PRL secretion showed very rapid on-off responses to nanomolar concentrations of the specific regulatory stimuli LHRH, TRH, vasoactive intestinal peptide, and dopamine. Aggregates remained highly responsive to LHRH even after 3 weeks in culture. The results indicate that isolated pituitary cells allowed to reaggregate in suspension culture form viable and functional multicellular structures which have maintained in vivo characteristics.
 ...
PMID:Ultrastructural and functional characteristics of rat pituitary cell aggregates. 679 74

An in vitro system for the incubation of mediobasal hypothalami (MBH) of cockerels and a radioimmunoassay for chicken luteinising hormone-releasing hormone-I (cLHRH-I) were developed. The size of the hypothalamic fragment (MBH including the median eminence) and the incubation conditions used (40 degrees C, under constant shaking and gassing) preserved the physiological properties of the tissue. It was possible to maintain the MBH in vitro and to study the LHRH release for several hours. The assay proved sensitive enough (ED80 = 0.794 pmol/tube, ie 4.59 pg/ml) and sufficiently precise (within-assay coefficient of variation = 4.4% and between-assay coefficient of variation = 10.2%) to measure the amounts of peptide released in the incubation medium. The use of this incubation system provided the first evidence of the stimulating effect of the excitatory amino acids glutamate, NMDA and kainate on the secretion of cLHRH-I in birds. Our results suggest that the effect on the NMDA receptor is predominant.
 ...
PMID:Release of chicken luteinising hormone-releasing hormone-I (cLHRH-I) by mediobasal hypothalamus in the cockerel: validation of an incubation system and effect of excitatory amino acids. 791 82

Several studies have demonstrated that the peptide LHRH can modify behavior in the male rat. Peripheral and intracerebral infusions of LHRH impair the acquisition of conditioned avoidance responses (CARs) and increase some spontaneous motor behaviors, such as head shaking and grooming. The present study was undertaken to detect the effects of LHRH on the acquisition of CARs and spontaneous motility in normally cycling and ovariectomized (OVX) Sprague-Dawley female rats. Normally cycling females were separated in four groups, according to the stage of the estrous cycle. Ovariectomized female rats were pretreated, 48 h before the experiment, with estradiol benzoate (10 microg/kg) or corn oil. LHRH (6.25, 25, or 50 microg/kg) was subcutaneously injected and the behavioral tests began 1 h after. Low doses of LHRH stimulated the acquisition of CARs during proestrus, estrus, and metestrus, whereas higher doses impaired conditioning in all the four stages of the cycle. High doses of LHRH impaired acquisition in OVX rats treated with oil and potentiated the depressant effects of EB on this behavior. The effects of LHRH on spontaneous motor activity were either stimulatory or inhibitory, according to the hormonal status and the dose administered. High doses of LHRH decreased motor responses in the diestrous rat. All the doses of LHRH increased the number of headshakes during proestrus, estrus, and metestrus, while the other motor responses were scarcely or not affected by LHRH in these stages. In OVX rats LHRH increased rearing, head shaking, and grooming behavior. These results support a role of LHRH in the modulation of conditioned and spontaneous behavior. They could provide an explanation to the behavioral changes observed across the estrous cycle and those observed after EB priming in OVX rats.
 ...
PMID:Effects of LHRH on avoidance conditioning in normally cycling and ovariectomized female rats. 976 56

Abstract The regulation of gonadotropin-releasing hormone (GnRH) secretion from the medial basal hypothalamus (MBH) of adult male rats has been studied using two types of in vitro methods, the dynamic superfusion and static incubation systems. We compared both systems for methodological features including stability of baseline GnRH release and technical limitations or artifacts as well as for response to norepinephrine and naloxone, an opiate antagonist, which represent the two major physiological neuromodulators regulating the GnRH neuron. Baseline GnRH release rate per MBH was similar in both systems for at least 6 h, although owing to dilution of effluent samples by flow-through medium, the dynamic superfusion system required six MBH per chamber compared with the static incubation system which required only one MBH per chamber. Procedural losses of GnRH were low with either system without the need for proteolytic enzyme inhibitors and were mainly due to adhesion to plastic surfaces of chambers and tubings in the dynamic superfusion system. Mechanical agitation of chambers by either manual swinging or continuous shaking increased GnRH release rate. Addition of hypertonic KCl (final 50 mM) or equivalent NaCl or mannitol solution in a minimal volume directly into the tissue chambers, induced a non-specific GnRH release due to osmotic effects in the dynamic superfusion system. In contrast, the static incubation system, where hypothalamic tissue is exposed to the exact final concentration of solute by complete change of media, was more resistant to GnRH release by hypertonic stimulus. Thus, only in the static incubation system did 50 mM KCl concentrations cause GnRH release through depolarization alone. Using systems optimized to avoid technical artifacts, stimulation with naloxone demonstrated dose-dependent GnRH release in both systems whereas norepinephrine gave a clear dose-dependent GnRH release only in the static system. Thus both incubation systems produce stable and similar baseline GnRH release for at least 6 h. The static incubation system proved superior requiring fewer hypothalami, a shorter preincubation stabilization period, allowing more accurate concentration of additives and was less prone to mechanical and osmotic artifacts while preserving responsiveness to physiological stimuli. The static incubation system, being technically simpler, more robust and accurate, provided a more valid approach to the in vitro study of GnRH release and its regulation by neurochemicals.
 ...
PMID:Hypothalamic Gonadotropin-Releasing Hormone Secretion: Methodological Aspects of in vitro Systems. 1921 20