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PubMed1973

The effects of heating and cooling the spinal cord and hypothalamus on thermoregulatory behaviour in the pig.

1. The effects of warming and cooling the spinal cord and hypothalamus on operant thermoregulatory behaviour and posture have been studied in the pig at neutral and cold ambient temperatures.2. Cooling the spinal cord increased and warming decreased the rate of obtaining thermal reinforcement. The response to cooling began with the onset of the stimulus and persisted for up to 5 min followed by a diminution in rate during the remaining 15 min of cooling. The peak of this ;on' response was greater the lower the ambient temperature. The response to heating was a small reduction in rate of reinforcement.3. The ;on' response to cooling the spinal cord was related to changes in temperature of only the cervical region of the cord.4. Cooling the hypothalamus led to an increase in the rate of obtaining heat and this increase was sustained during the 20 min of central cooling. Termination of cooling was followed by a marked depression in rate. Heating the hypothalamus had only a weak inhibitory effect on rate of reinforcement.5. While working for external heat during periods when thermodes over the spine and in the hypothalamus were not being cooled, pigs lay in ;cold defensive' prone positions 25% of the time and lay on their sides 75% of the time. During cooling of the spinal cord the time spent in the prone position was 95% at 5 and 15 degrees C ambients and 71% at a 25 degrees C ambient. During cooling of the hypothalamus the prone posture was adopted 50% of the time.6. When the temperatures of the spinal cord and of the hypothalamus were changed in opposite directions, the operant response was determined by the temperature of the hypothalamus while the postural response was most frequently determined by the temperature of the spinal cord.

Animals↗
PubMed1974

Stimulation of the hypothalamus and ovulation in the guinea-pig.

1. Various methods of stimulating the hypothalamus were applied to the guinea-pig with the aim of inducing ovulation.2. Electrochemical stimulation of the hypothalamus, or gross stimulation of the brain, was ineffective.3. Electrical stimulation of the medial basal hypothalamus or rostral hypothalamus elicited gonadotrophin release.4. Despite variation of the time and intensity of stimulation, follicular luteinization was more common than the formation of new corpora lutea.5. Electrical stimulation of the medial basal hypothalamus often caused luteinization of follicles. Fewer animals responded to excitation of the rostral hypothalamus, but in those that did, ovulation occurred more frequently.6. The present observations contrast markedly with comparable studies on the rat, where both electrochemical and electrical stimulation of the hypothalamus readily induce ovulation.

Animals↗
PubMed2000

Cardiovascular responses to NMDA injected into nuclei of hypothalamus or amygdala in conscious rats.

The nuclei of hypothalamus and amygdala have been shown to be involved in the central cardiovascular homeostasis. Recent studies suggest that glutamate-containing neurons have an important role in the regulation of the central cardiovascular function. In this study, we demonstrate the roles of the central nucleus of the amygdala and the paraventricular nucleus of the amygdala and the paraventricular nucleus or the dorsomedial nucleus of the hypothalamus in N-methyl-D-aspartate (NMDA) induced blood pressure and heart rate changes in conscious Sprague-Dawley rats. Intracerebroventricular or parenchymal injections of NMDA evoke increases in arterial pressure. The NMDA-induced elevations in blood pressure are more prominent when NMDA is administered into the dorsomedial nucleus of the hypothalamus. Microinjections of NMDA into the dorsomedial hypothalamus exert significant heart rate increases, whereas NMDA when administered into the paraventricular nucleus of the hypothalamus or into the central nucleus of the amygdala has no significant effect on the heart rate. The dorsomedial nucleus of the hypothalamus is found to be the most effective site in this respect. The present study provides strong evidence for the tonic glutamatergic influence on blood pressure and heart rate via NMDA receptors located within the dorsomedial nucleus and to a lesser extent via those located within the paraventricular nucleus of the hypothalamus.

Amygdala↗
PubMed2005

Effects of injecting thymulin into the anterior or medial hypothalamus or the pituitary on induced ovulation in prepubertal mice.

UNLABELLED: In prepubertal mice, subcutaneous thymulin injection before equine chorionic gonadotrophin (eCG) treatment simulates ovulation; seemingly, the thymulin could be acting at the hypothalamus-pituitary axis level. OBJECTIVE: This study was designed to analyze the effects of injecting thymulin into the hypothalamus or pituitary on induced ovulation of prepubertal mice. METHOD: Female mice, 19 days old, were anesthetized with ether and injected with saline solution or thymulin into the anterior or medial hypothalamus or the pituitary and treated with eCG when 20 days old. The ova shed were counted and serum concentrations of 17beta-estradiol were measured. In the ovaries, the morphometrical analysis was performed and the atresia evaluated. RESULTS: Ether anesthesia treatment blocked eCG-induced ovulation in almost all animals. Mice anesthetized and treated with eCG and gonadotrophin-releasing hormone (GnRH) or human chorionic gonadotrophin (hCG) ovulated a full quota of ova. Injecting saline solution into the anterior or medial hypothalamus or the pituitary did not reduce the blocking effects of ether anesthesia on induced ovulation, but the incidence of atretic follicles was higher. Injecting thymulin directly into the anterior hypothalamus did not restore ovulation, nor diminish the number of atretic follicles. In contrast, injecting thymulin into the medial hypothalamus restored the ovulation ratio and decreased the percentage of atretic follicles. Similar results were obtained by injecting thymulin into the pituitary, though thymulin treatment in the pituitary resulted in a higher number of ova shed and lower follicular atresia. CONCLUSION: The present results suggest that thymulin acts at the medial hypothalamus level, facilitating the release of GnRH and at the pituitary level regulating gonadotrophin release.

Animals↗
PubMed1989

Immunoreactive prolactin in the hypothalamus and cerebrospinal fluid of male and female rats.

Immunoreactive prolactin (ir-PRL) has been identified in the cerebrospinal fluid (CSF) and brain of the male and female rat. In this study we determined the concentration of ir-PRL in the CSF and hypothalamus under conditions known to increase or decrease serum PRL. Hypophysectomy (60 days) significantly decreased the concentration of ir-PRL in the CSF of male (4.9 +/- 0.7 vs. 3.0 +/- 0.3 ng/ml) and female (5.8 +/- 0.9 vs. 3.1 +/- 0.5 ng/ml) rats. However, the effect of long-term hypophysectomy on hypothalamic ir-PRL was gender-dependent. That is, in the male rat hypophysectomy did not affect the content of ir-PRL in the female rat, long-term hypophysectomy decreased the content of ir-PRL in the median eminence, ventral hypothalamus, and dorsal hypothalamus 37, 40, and 47%, respectively. Estradiol replacement to the hypophysectomized female rat normalized the content of ir-PRL in the median eminence (96 +/- 5.8 to 131 +/- 9.6 ng/mg protein), ventral hypothalamus (11 +/- 0.6 to 16.0 +/- 1.1 ng/mg protein), dorsal hypothalamus (4.7 +/- 0.4 to 8.6 +/- 0.4 ng/mg protein), and the concentration ir-PRL in the CSF (2.5 +/- 0.3 to 4.6 +/- 0.4 ng/ml). In intact female rats, administration of haloperidol induced a marked hyperprolactinemia, and significantly increased CSF ir-PRL (5.1 +/- 1.5 vs. 18.0 +/- 3.8 ng/ml). However, in the same rats, the content of ir-PRL in the median eminence was significantly decreased while the ir-PRL content in the ventral hypothalamus and dorsal hypothalamus was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Organization of the lateral hypothalamus for control of adrenocorticotropin release in the cat.

Regions in the ventral midbrain that project to the lateral hypothalamus have been implicated in the control of ACTH release. To define further those areas in the lateral hypothalamus through which afferent signals might pass, we electrically stimulated 188 sites in the lateral hypothalamus of 20 cats anesthetized with chloralose-urethane. Stimulations were monophasic pulses of DC (200 microA; 0.2 msec; 100 Hz; 20 sec). Venous samples were drawn over 30 sec 0.5 min before and 1.5 min after stimulation. Equal volumes of warmed isoncotic dextran were infused during sampling to prevent hypovolemia. ACTH was assayed by RIA. Areas were defined in which stimulation led to increased, decreased,, or unchanged ACTH. Mean changes in ACTH were tested by analysis of variance. The present data indicate that the ACTH-active areas defined previously in the midbrain may join the medial forebrain bundle in the subthalamic area and nucleus to traverse the lateral hypothalamus. At the level of the mammillary bodies, a facilitatory area occupied the ventral portion of the medial forebrain bundle. This area extended rostrally and medially to join the medial aspect of the medial forebrain bundle. Continuity with the mediobasal hypothalamus was seen only anteriorly in the area of the supraoptic decussations. An inhibitory area occupied the dorsal extent of the medial forebrain bundle at the level of the mammillary bodies. It extended rostrally and laterally around the caudal pole of the supraoptic nucleus and then medially at the level of the optic chiasm. There appear to be no other medial projections of the lateral lying ACTH-active areas to the mediobasal hypothalamus. The lateral hypothalamus may serve as a site of passage and/or of processing of information that ascends from the midbrain and descends from the limbic system.

Adrenocorticotropic Hormone↗
PubMed1985

Distribution and regulation of aromatase activity in the rat hypothalamus and limbic system.

Conversion of androgen to estrogen in the rat brain is catalyzed by aromatase enzymes. The maximum concentrations of these enzymes are found within the hypothalamus and amygdala, where they appear to play an important role in the process by which androgens affect both behavior and neuroendocrine function. In the present study, we measured the levels of aromatase activity (AA) in 20 nuclei and brain regions of the adult rat brain. Individual nuclei were microdissected from 600-micron frozen sections. Tissues from 3 animals were pooled, and AA was measured by an in vitro radiometric assay that quantifies the stereospecific production of 3H2O from [1 beta-3H]androstenedione as an index of estrogen formation. We report that AA is heterogeneously distributed within the rat brain. The greatest amounts of activity were found in the bed nucleus (n.) of the stria terminalis (700 protein fmol/h . mg) and in the medial (MA) and cortical amygdala (400-600 fmol/h . mg protein) of the male. There was an evident rostral-caudal and medial-lateral gradient in AA throughout the diencephalon. Activity was high in the periventricular preoptic n. and medial preoptic n.; intermediate in the suprachiasmatic preoptic n., anterior hypothalamus, periventricular anterior hypothalamus, and ventromedial n.; and low in the arcuate n.-median eminence, lateral preoptic n., supraoptic n., dorsomedial n., and lateral hypothalamus. Regions devoid of measurable AA included the medial and lateral septum, caudate-putamen, hippocampus, and parietal cortex. In the female, AA was greatest in the MA and cortical amygdala. We found that AA in the MA, stria terminalis n., suprachiasmatic preoptic n., periventricular preoptic in., medial preoptic n., anterior hypothalamus, and ventromedial n. was significantly greater (P less than 0.05) in males than in females. Orchidectomy reduced AA to levels seen in females, and administration of testosterone to castrated males restored AA in these areas. No significant sex differences were observed in any other hypothalamic or amygdaloid nuclei, although AA was increased by testosterone treatment in the periventricular anterior hypothalamus, arcuate n.-median eminence, and lateral hypothalamus. Our results provide a quantitative profile of AA in specific hypothalamic and limbic nuclei of the rat brain as well as information on the control of AA within these discrete regions.

Androstenedione↗
PubMed2004

[The developmental changes of GHR and IGF-1R gene expressions in porcine hypothalamus and pituitary].

GH and IGF-1 may serve as negative feedback factors to regulate GH secretion from pituitary by binding to their respective receptors in hypothalamus and/or pituitary. In order to evaluate the line-specific developmental patterns of negative feedback regulation of GH secretion, Erhualian (EHL) and Large White (LW) pigs with significant difference in growth rate were employed in present study to investigate the developmental changes of GH receptor (GHR) mRNA and type-1 IGF receptor (IGF-1R) mRNA in hypothalamus and pituitary from birth till 180 days of age by relative quantitative RT-PCR. Pigs were sampled at birth, 3 , 20, 30, 90, 120 and 180 days of age respectively. Hypothalamic GHR mRNA was expressed according to an age-dependent manner, being low at birth, then increased steadily till day 120, followed by a decrease (P < 0.05) at the age of 180 days, suggesting that the sensitivity of hypothalamus to the GH negative feedback influence increase steadily during fast-growing period. LW boars expressed higher level of GHR mRNA than EHL boars (P < 0. 05) in hypothalamus. In pituitary, however, the GHR mRNA level was not significantly correlated with the breeds and age. The results suggested that GH might act mainly at the level of hypothalamus to regulate GH secretion. In contrast, the expression of IGF-1R mRNA exhibited line-specific developmental patterns in pituitary but not in hypothalamus. Hypothalamic expression of IGF-1R mRNA was abundant but did not show significant differences between ages, groups or lines. In pituitary, however, the IGF-1R mRNA expression was found to be high at birth both in EHL and LW pigs, subsequently declined till day 20, then followed by a slow rise reaching the second peak at the age of 90 days. At the age of 180 days, the pituitary IGF-1R mRNA level was higher in EHL pigs than that in LW pigs (P < 0.05), but the opposite was true at the age of 30 and 90 days. These results suggest that the site for receiving the feedback signal of IGF-1 is more likely in pituitary rather than in hypothalamus in the pig.

Age Factors↗
PubMed1985

[Levels of catecholamines in the hypothalamus, hypophysis and in the adrenal in sheep after whole-body exposure to gamma rays].

The changes were studied in the levels of catecholamines and L-DOPA in the control system of reproduction cycle (hypothalamus, hypophysis) and in adrenal glands of sheep after all-body irradiation with 60Co at the total dose of 6.7 Gy for seven days. The power input per hour of irradiation source was 0.039 Gy. The catecholamines (noradrenaline, dopamine and adrenaline) and L-DOPA were determined, after having been isolated from the tissues, by the method of spectral fluorimetry. After all-body exposition to gamma-radiation noradrenaline dropped in hypothalamus in comparison with the control group of sheep, most significantly in the rostral (by 74.2%) and caudal part (by 40%). A similar drop like in the case of noradrenaline was also observed in dopamine, the concentrations of which decreased in rostral hypothalamus by 72%, in medial hypothalamus by 94% and in caudal hypothalamus by 60%. Adrenaline shows a drop in hypothalamus, most significant in caudal region (by 62%). In relation with that the level of a precursor for the synthesis of catecholamines and L-DOPA has been changed which achieved, in the studied regions of hypothalamus in sheep, significantly lower levels than were determined in the control group of sheep. As regards the hypophysis, after irradiation no significant changes in the levels of noradrenaline and adrenaline were recorded, however, dopamine and L-DOPA dropped significantly (P less than 0.01). The exposition to gamma-radiation also causes a decrease in the concentrations of catecholamines and L-DOPA in the adrenal glands of sheep, most significant in noradrenaline (by 61%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Variations in number of dopamine neurons and tyrosine hydroxylase activity in hypothalamus of two mouse strains.

Mice of the BALB/cJ strain have more neurons and greater tyrosine hydroxylase (TH) activity in the midbrain than mice of the CBA/J strain (Baker, H., T. H. Joh, and D. J. Reis (1980) Proc. Natl. Acad. Sci. U.S.A. 77: 4369-4373). To determine whether the strain differences in dopamine (DA) neuron number and regional TH activity are more generalized, regional TH activity was measured and counts of neurons containing the enzyme were made in the hypothalamus of male mice of the BALB/cJ and CBA/J strains. TH activity was measured in dissections of whole hypothalamus (excluding the preoptic area), the preoptic area containing a rostral extension of the A14 group, the mediobasal hypothalamus containing the A12 group, and the mediodorsal hypothalamus containing neurons of the A13 and A14 groups. Serial sections were taken and the number of DA neurons was established by counting at 50- to 60-microns intervals all cells stained for TH through each area. In conjunction with data obtained biochemically, the average amount of TH per neuron was determined. In all areas, TH activity in CBA/J mice was significantly less (p less than 0.001) than in BALB/cJ mice, ranging from 48% in the mediobasal hypothalamus to 71% in the medial and dorsal hypothalamus. The number of TH-containing neurons was also significantly less in the CBA/J strain (p less than 0.001), ranging from 49% in the preoptic area to 74% in the mediobasal hypothalamus (MBH). With the exception of the MBH, enzyme activity per neuron was similar in both strains. In the MBH, strain differences in TH activity were greater than those for neuron number, resulting in less TH activity per neuron in the CBA/J strain. The results suggest that strain differences in the number of DA neurons are widespread and involve DA systems throughout the brain. Therefore, differences in whole brain TH activity cannot be attributed only to differences in specific regions. Our findings further support the view that the number of neurons of a specific chemical class may be under genetic control.

Animals↗
PubMedDate not supplied

[Luteinizing hormone content in the hypothalamus in relation to the physiological status of rats].

Content and relative concentration (per 1 mg of protein) of luteinizing hormone (LH) varied in rat hypothalamus depending on the animal sex and age. In hamster hypothalamuses the hormone content correlated with the state of sexual cycle; maximal content of LH was found during estrus. Content of LH in hypothalamus depend also on the effect of light (rhythmic illumination, permanent light or darkness, duration of the light effect). After gonadectomy content of LH was increased in hypothalamus of female rats within 60 days. Simultaneous hypophys- and ovariectomies increased the LH content in hypothalamus already within 14 days after the treatment. Whole-body perfusion of rats did not alter the LH content in hypothalamus. LH was found in the middle and posterior parts of hypothalamus, particularly, in arcuate nucleus, middle eminence and mammillary bodies.

Animals↗
PubMedDate not supplied

The vasopressor and oxytocic activities of the hypothalamus and neurohypophysis are influenced by inhibited alpha-adrenergic transmission during dehydration and subsequent rehydration in the white rat.

During equilibrated water metabolism a single dose of dihydroergotamine (DHE) increased vasopressin release from the neurohypophysis; it had no effect on oxytocin content in the hypothalamus and neurohypophysis. After two days of dehydration DHE somewhat restrained the decrease of oxytocin in the hypothalamus; the release of vasopressin from the neurohypophysis was then increased. Under severe dehydration, i.e. under conditions of potent osmoreceptor stimulation, DHE influenced the vasopressin content neither in the hypothalamus nor in the neurohypophysis, but in some way it intensified oxytocin depletion in the neurohypophysis. Following two days of rehydration DHE somewhat restrained the renewal of vasopressin in the hypothalamus. No changes of oxytocin in the hypothalamus could be demonstrated at that time; in the neurohypophysis DHE intensified vasopressin repletion, but inhibited oxytocin repletion. Following four and eight days of rehydration DHE had no influence on vasopressin repletion rate in the hypothalamus and neurohypophysis. At that time oxytocin repletion in the neurohypophysis was increased; in the hypothalamus it was not affected by DHE. It is concluded that the response of the hypothalamo-neurohypophyseal system to alpha-adrenergic blockade-as brought about by dihydroergotamine treatment-seems to be dependent on the actual state of water metabolism. Impulses from the osmoreceptors may be therefore of some important in modifying the change in vasopressin and oxytocin release resulting from inhibition of alpha-adrenergic transmission through neural chains including units susceptible to dihydroergotamine.

Animals↗
PubMed1994

Estradiol reduction of the agonist high affinity form of the alpha 2-adrenoceptor in the hypothalamus of female rats: identification as the alpha 2D subtype.

These studies examined which alpha 2-adrenoceptor subtype is expressed in the hypothalamus and preoptic area and the influence of estradiol administration on alpha 2-adrenoceptors in the hypothalamus of female rats. The alpha 2-adrenoceptor antagonist [3H] RX821002 bound to a single site in hypothalamus, preoptic area, and cortex membranes, with high affinity and low nonspecific binding, as determined by Scatchard and kinetic binding analyses. Competition for [3H]RX821002 binding in the hypothalamus and preoptic area by various noradrenergic agonists and antagonists revealed a unique pharmacological specificity with a high degree of similarity to that of the alpha 2D-adrenoceptor. Norepinephrine displacement of [3H]RX821002 binding in hypothalamic membranes from ovariectomized animals was monophasic and characterized by high affinity. In contrast, norepinephrine competition for [3H]RX821002 binding sites in the hypothalamus from rats exposed to estradiol for 48 hr was biphasic, and norepinephrine bound to both a high (18%) and a low (82%) affinity site in these membranes. Thus, the formation of agonist high affinity alpha 2D-adrenoceptor complexes was inhibited by prior exposure to estrogen. In both control and estradiol-exposed hypothalamic membranes, 100 microM 5'-guanylylimidodiphosphate [Gpp(NH)p] converted the norepinephrine competition curves to ones characterized by monophasic, low affinity binding. In addition, binding of the full alpha 2-adrenoceptor agonist [3H]UK-14,304 in the hypothalamus and preoptic area of female rats was concentration-dependently diminished by Gpp(NH)p treatment. Complete loss of [3H]UK-14,304 binding was effected by 100 microM Gpp(NH)p. This suggests that [3H]UK-14,304 may be useful in labeling the agonist high affinity state of alpha 2-adrenoceptors. Decreasing the incubation temperature in saturation studies from 25 degrees to 0 degrees increased [3H]UK-14,304 binding in hypothalamic membranes of control rats but not in membranes from estradiol-treated rats. Estradiol treatment for 48 hr decreased [3H]UK-14,304 binding in hypothalamic membranes by 34% (0 degrees) to 60% (25 degrees), without changing the Kd. These results suggest that the alpha 2D-adrenoceptor is the predominant subtype in the hypothalamus and preoptic area of female rats and that estradiol treatment markedly reduces the number of alpha 2D-adrenoceptors in the agonist high affinity state.

Adrenergic alpha-Agonists↗
PubMed1996

Efferent projections from the ovarian steroid receptor-containing area of the ventrolateral hypothalamus in female guinea pigs.

The ventrolateral hypothalamus (VLH) in female guinea pigs includes a subset of neurons which contain estrogen and progestin receptors, and which are implicated in the regulation of female sexual behavior by steroid hormones. However, little is known about where these neurons project, and consequently which other brain areas are involved in sexual behavior in female guinea pigs. The anterograde tracer Phaseolus vulgaris-Leucoagglutinin was used to label efferents from the ovarian steroid receptor-containing part of the VLH. To identify the correct placement of the tracer specifically within the group of neurons containing estrogen receptors, medial hypothalamic sections were also immunostained for estrogen receptors. Forebrain areas receiving dense projections from the ventrolateral hypothalamus included the bed nucleus of the stria terminalis, medial preoptic area, anterior hypothalamic area, anterior ventromedial hypothalamus, and caudal ventrolateral hypothalamus. The midbrain central gray was also heavily labeled. Moderate innervation was observed in the forebrain in the basolateral amygdala, medial preoptic nucleus, lateroanterior hypothalamic nucleus, dorsal hypothalamic areas, posterior hypothalamus, zona incerta, and in the midbrain interspersed among the central and lateral tegmental tracts. The major efferent pathways from the VLH appeared to travel rostrally through the mediobasal hypothalamus and preoptic area, and caudally via the medial thalamic nuclei and periventricular fiber system. These findings are similar to those of previous studies tracing the efferents from the ventromedial nucleus in rats and from the lateral hypothalamus in guinea pigs. Many of these areas that receive input from the steroid receptor rich area within the VLH are likely to be involved in the regulation of female sexual behavior.

Animals↗
PubMed1977

[Response of neurons of the anterior and posterior regions of the hypothalamus to stimulation of the vagus and sciatic nerves and photic stimulation].

Evoked activity of single units in anterior and posterior hypothalamus to vagal, sciatic nerves, and photic stimulation was studied in anesthetized and immobilized cats. The responsiveness of neurons of the posterior hypothalamus was 66, 77 and 37% to vagal, sciatic nerves and photic stimulation, respectively, and of the anterior hypothalamus -- 47, 62 and 48%. Vagal stimulation was found to be the more effective for units of the posterior hypothalamus. Responses of units to a flash prevailed in the anterior hypothalamus. 78% of convergence of viscero-somatic afferentation on neurons of the posterior hypothalamus and 62% -- on anterior hypothalamic neurons, were revealed. The responses to all kinds of afferent stimuli were phasic and of excitatory character. Possible role and mechanisms of vagal interoceptive activation of hypothalamic units are discussed.

Animals↗
PubMed1990

Excitotoxic lesions of the paraventricular hypothalamus: metabolic and cardiac effects.

The excitotoxin, N-methyl-D-aspartic acid (NMDA), was used to lesion cell bodies, but not fibers-of-passage, in the paraventricular hypothalamus. Bilateral injections of NMDA (12.6 nmol/100 nl) were made into the paraventricular hypothalamus in halothane-anesthetized male Sprague-Dawley rats. Water intake, food intake, urine output and body weight were measured daily for 26 days after lesioning. Lesioned rats exhibited a modest, but significant, reduction in the rate of gain of body weight, which was most closely correlated with decreases in food intake. Water intake and urine output were not significantly different among the groups. Resting blood pressure, heart rate and baroreflex sensitivity (using the infusion of phenylephrine method) were similar in conscious animals of both groups, 4-5 weeks after lesioning. Neuronal loss, primarily of parvocellular elements, was evident in the paraventricular hypothalamus and neuronal loss frequently extended into the ventro-medial thalamus adjacent to the paraventricular hypothalamus in NMDA-lesioned rats. In a second experiment, injections of NMDA were given acutely into the paraventricular hypothalamus of halothane-anesthetized rats. Upon recovery from anesthesia, behavioral excitation and increases in blood pressure and heart rate were evident for 1-2 hr. Histological examination of hearts taken 48 hr after injection of NMDA revealed a largely mononuclear inflammatory infiltration, hyperemia and myocardial hemorrhage and focal myocardial necrosis. Inflammatory and degenerative changes were most prominent in the left ventricular subendocardium. The cardiomyopathy possessed similarities with catecholamine-induced myocardial necrosis. The results indicated that NMDA-induced lesions of parvocellular elements of the paraventricular hypothalamus did not cause hyperphagia or obesity or alter the resting systemic circulatory function. However, an inflammatory cardiomyopathy, termed "excitotoxin-induced myocardial necrosis", was associated with injections of NMDA into the hypothalamus. Excitotoxin-induced myocardial necrosis may complicate any hemodynamic studies performed in rats in which lesions of the CNS have been produced by means of application of excitotoxins.

Animals↗
PubMed1997

Microinjection of the tachykinin neuropeptide K into the ventromedial hypothalamus disrupts the hormonal onset of maternal behavior in female rats.

The medial amygdala exerts an inhibition of maternal behavior in virgin rats, but neither the site to which it projects to exert this effect nor the neurotransmitter used in such a pathway is known. There is also evidence that the ventromedial nucleus of the hypothalamus exerts an inhibition of maternal behavior, and the medial amygdala projects to this nucleus, suggesting that it may receive a projection from the medial amygdala which is inhibitory for maternal behavior. Tachykinin injection into the hypothalamus inhibits reproductive behavior in male rats, and there is a tachykininergic projection from the medial amygdala to the ventromedial hypothalamus. Consequently, the present study was conducted to evaluate the hypothesis that the tachykinin neuropeptide K can inhibit maternal behavior after injection into the ventromedial hypothalamus. Female rats were primed to be maternal by pregnancy termination and estrogen injection. Four doses of the peptide (279 pmol, 186 pmol, 116 pmol, and 66 pmol) were bilaterally injected into the ventromedial hypothalamus, and all were effective in delaying the onset of maternal behavior. Evidence that neuropeptide K disrupts maternal behavior in animals that have already begun to be maternal is also presented. Site specificity of neuropeptide K's effect to within the region of the ventromedial hypothalamus was supported, as injection into the mediodorsal thalamus was without effect. Some possibly relevant neuroendocrine effects are addressed, as well as the possibility that tachykinins may act within the ventromedial hypothalamus to promote virgin female rats' fear of pup odors.

Animals↗
PubMed2004

[Study on effect and mechanism of liuwei dihuang decoction in modulating hypothalamus-pituitary-ovary axis in senescence accelerated mice model].

OBJECTIVE: To study the changes of hypothalamus-pituitary-ovary (HPO) axis of senescence accelerated mice (SAM) model in their aging process and the modulatory effect of Liuwei Dihuang decoction (LW) on the changes. METHODS: Using vaginal smear to test the estrous cycle of animal; using radioimmunoassay to determine serum levels of estradiol (E2), and beta-endorphin (beta-EP) and substance P (SP) in hypothalamus; and the western bloting technique was adopted to quantify the level of luteinizing hormone (LH) in pituitary and estradiol receptor alpha (ER alpha) in pituitary and ovary. RESULTS: The estrous cycle and diestrus were significantly prolonged as SAMP8 aged, the concentration of serum E2 was lower, pituitary LH was higher in the SAMP8 than those in SAMR1. Content of beta-Ep and SP in hypothalamus gradually lowered during aging, SP content lowered after a transient increasing, and ER alpha expression lowered significantly. LW could significantly shorten the diestrus, increase weight of ovary, elevate serum E2 level, significantly reduce the LH level in pituitary, increase beta-EP content in hypothalamus and ER alpha expression in ovary, but significantly lower SP content in hypothalamus. Oral administration of estrogen could increase serum E2, beta-EP and SP content in hypothalamus and ER alpha expression in pituitary, but lower LH level in pituitary, weight of ovary and ER alpha level in ovary. CONCLUSION: SAMP8, in the aging process, develops a progressive HPO axis functional disturbance, it is closely related with the change of levels of peptide neuro-mediator in hypothalamus and change of ER alpha level in ovary. LW could improve or modulate the HPO axis functional disturbance in SAMP8.

Aging↗