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  • 1
    Electronic Resource
    Electronic Resource
    Bursting activity in tuberoinfundibular neurones during electrical stimulation of the rostral hypothalamus (1980)
    Springer
    Experimental brain research 39 (1980), S. 113-116 
    Details
    ISSN: 1432-1106
    Keywords: Tuberoinfundibular neurones ; Hypothalamic stimulation ; Bursting activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The firing of tuberoinfundibular neurones antidromically identified as projecting to the median eminence was recorded during electrical stimulation of the preoptic and/or anterior hypothalamic areas (PO/AH) of the rostral hypothalamus. Parameters of stimulation were chosen which are known to cause increased secretion of most adenohypophyseal hormones. Twenty-three of 58 neurones were excited during the periods of stimulation and approximately half of these excited cells fired in a bursting fashion reminiscent of that previously observed in other endocrine neurones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237074
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  • 2
    Electronic Resource
    Electronic Resource
    Discharge of gonadotrophin-releasing hormone from the mediobasal part of the hypothalamus: Effect of stimulation frequency and gonadal steroids (1980)
    Springer
    Experimental brain research 39 (1980), S. 453-460 
    Details
    ISSN: 1432-1106
    Keywords: Gonadotrophin-releasing hormone ; Hypothalamic stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The release of gonadotrophin-releasing hormone (Gn-RH), in response to electrical stimulation of the mediobasal part of the hypothalamus incubated in vitro, was studied in both male and female rats. In male rats significant release of Gn-RH occurred during the 10-min experimental period only when the incubated tissue was stimulated at frequencies of 10 Hz or greater. There was no release when stimulated at 5 Hz. There was also no release of hormone when the mediobasal hypothalami were incubated in a Ca2+ free medium. The amount of Gn-RH released during a 10-min incubation period increased progressively as the frequency of stimulation was raised from 10–100 Hz. During short (4-min) incubation periods the effectiveness of each stimulus pulse for Gn-RH release also increased with the frequency of stimulation. However, when stimulated for 10 min there was no increase in hormone released per stimulus pulse when frequency of stimulation was raised above 10 Hz. The amount of Gn-RH released in response to stimulation at 50 Hz was greater in male rats than in females. For the females, there was no significant difference between the amounts of Gn-RH released at dioestrus and pro-oestrus. In both male and female rats gonadectomised 4 weeks prior to hypothalamic incubation, the response to electrical stimulation at 50 Hz was reduced when compared with intact controls. Indeed, for the females there was no longer a statistically significant increase in the amount of Gn-RH in the incubation medium after 50 Hz stimulation. Ovariectomised female rats, injected twice daily for 3.5 days with 20 μg of oestradiol benzoate released Gn-RH in response to 50 Hz stimulation in the same amounts as intact control animals. By contrast, there was no recovery of Gn-RH release to normal levels in castrated male rats similarly treated with 1.25 mg testosterone propionate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239310
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  • 3
    Electronic Resource
    Electronic Resource
    Evidence for a direct effect of LRF and TRF on single unit activity in the rostral hypothalamus (1974)
    [s.l.] : Nature Publishing Group
    Nature 252 (1974), S. 486-488 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Female rats were anaesthetised with urethane and prepared for extracellular recording of single unit activity8. Action potentials were recorded through glass micropipettes?filled with 4.0 M sodium chloride?with a tip resistance of 5?15MW, which constituted the centre barrel of multi-barrelled ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/252486a0
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  • 4
    Electronic Resource
    Electronic Resource
    Opioid peptides inhibit the release of noradrenaline from slices of rat medial preoptic area (1987)
    Springer
    Experimental brain research 66 (1987), S. 378-384 
    Details
    ISSN: 1432-1106
    Keywords: Noradrenaline ; Opioids ; Medial preoptic area ; Luteinising hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous circumstantial evidence suggested that endogenous opioid peptides inhibit an excitatory noradrenergic projection to the medial preoptic area (MPOA), and thereby suppress the activity of neurones containing luteinising hormone-releasing hormone and thus systemic concentrations of luteinising hormone (LH) itself. In this paper, we report that electrically stimulated release of 3H-Noradrenaline (3H-NA) from perifused slices of rat MPOA is diminished when opioid agonists are added to the incubation medium. Thus, morphine (10 μM), beta-Endorphin (1 μM) and met-Enkephalin (1 μM), but not Dynorphin A (1–8) (1 μM), caused a significant decrease in electrically stimulated 3H-NA release. The inhibition was reversed by addition of naloxone (10 μM) to the perifusion medium but 3H-NA release was unaffected by dopamine or acetylcholine (or their antagonists sulpiride and atropine, respectively), or serotonin, neurotensin, muscimol or bicuculline (the latter two being agonist and antagonist respectively for the GABA A receptor). Therefore, the experiments provide direct evidence that brain opioids modulate the noradrenergic input to MPOA neurones and support the hypothesis that this may be one mechanism for the regulation of LH secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243311
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  • 5
    Electronic Resource
    Electronic Resource
    Role of medial preoptic GABA neurones in regulating luteinising hormone secretion in the ovariectomised rat (1991)
    Springer
    Experimental brain research 87 (1991), S. 345-352 
    Details
    ISSN: 1432-1106
    Keywords: γ-aminobutyric acid ; Bicuculline ; Medial preoptic area ; Microdialysis ; Luteinising hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The role of GABA neurones in the medial preoptic area (MPOA) in regulating the activity of the luteinising hormone-releasing hormone (LHRH) neurones projecting to the median eminence was investigated in the conscious ovariectomised rat. Plasma luteinising hormone (LH) concentrations were measured while (1) endogenous GABA release from the MPOA was monitored with the technique of microdialysis, or (2) activity at the GABA receptor was modulated by local infusions into the MPOA. Microdialysis studies revealed a fluctuating level of GABA release in the MPOA which did not correlate with pulsatile LH secretion. Infusion of 10 μM GABA (n=8) or bicuculline methiodide (BMI, n=6) into the MPOA, at a rate of l μ1/30 min, significantly inhibited mean LH concentrations (P〈 0.05-0.001) and LH pulse frequency (P〈 0.05-0.001) compared with controls (n = 8). LH pulse amplitude was not significantly altered by infusion of GABA (P〉 0.05) while too few pulses were found after BMI treatment to enable statistical analysis. Infusions of GABA into the ventral half of the MPOA had a more significant inhibitory effect upon LH secretion compared with dorsal infusions (P=0.012). A similar relationship did not exist for BMI infusions. These results show that acute changes in preoptic GABA receptor occupancy result in disruption of pulsatile LH secretion in the ovariectomised rat. This suggests that GABA neurones provide a tonic input important for the functional integrity of the neural network controlling LH secretion. However, as changes in extracellular GABA concentrations in the MPOA do not correlate with pulsatile LH release, the preoptic GABA population, as a whole, is unlikely to be directly responsible for the pulsatile activity of the LHRH neurones in the ovariectomised rat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231851
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  • 6
    Electronic Resource
    Electronic Resource
    Opioid binding in the rostral hypothalamus is reduced following lesion of the ventral noradrenergic tract in female rats (1991)
    Springer
    Experimental brain research 85 (1991), S. 230-234 
    Details
    ISSN: 1432-1106
    Keywords: Preoptic area ; Opioid binding ; Diprenorphine ; Noradrenergic transmission ; Ventral noradrenergic tract lesion ; Autoradiography ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were undertaken to establish whether opioid receptors exert a direct presynaptic influence on noradrenergic (NA) terminals in the preoptic/ anterior hypothalamus (PO/AH) of the female rat. Thus, opioid binding studies were performed in rats with lesions of the ventral NA tract (VNAT; the main NA projection to the hypothalamus) to assess whether a loss of NA terminals may also result in a decrease in opioid binding in the PO/AH. In the first experiment, unilateral electrolytic lesions of the VNAT caused a significant reduction in both the NA content and specific [3H]-diprenorphine binding to membrane homogenates in the ipsilateral PO/AH. In the second experiment bilateral 6-hydroxydopamine (6-OHDA)-induced lesions of the VNAT caused a significant reduction in NA levels in the PO/AH as well as significant decreases in the density of [3H]-diprenorphine binding to tissue sections of the PO/AH when compared to control animals. These results strongly suggest that the NA input to the PO/AH is regulated by endogenous opioid peptides, and provide an anatomical substrate to explain opioid-NA interactions in the control of gonadotrophin releasing hormone (GnRH) and gonadotrophin secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230005
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  • 7
    Electronic Resource
    Electronic Resource
    Reproducible increases in intramammary pressure after spinal cord stimulation in lactating rats (1984)
    Springer
    Experimental brain research 55 (1984), S. 313-316 
    Details
    ISSN: 1432-1106
    Keywords: Milk-ejection ; Spinal cord ; Stimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intramammary pressure was recorded in anaesthetized lactating rats during electrical stimulation of the anterolateral pathways in the T12/L1 region of the spinal cord. In 18 rats, electrical stimulation at 10 Hz or more for 10–30 s caused a reproducible increase in intramammary pressure. The mammary gland responses were similar to those resulting from stimulation of the neurohypophysis with the same parameters, and were eliminated after complete destruction of the neural stalk; they were not associated with any consistent change in blood pressure. In 3 rats, a mammary gland response to spinal cord stimulation was obtained only after administration of the β-adrenergic blocker, propranolol, which facilitates suckling-induced reflex milk-ejections. These results suggest that spinal cord stimulation can cause the release of oxytocin; the functional significance of such a release is discussed in relation to the milk-ejection reflex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237281
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical stimulation of the hypothalamus: New observations on the parameters necessary for ovulation in rats anaesthetised with pentobarbitone during the pro-oestrous “critical period” (1978)
    Springer
    Experimental brain research 33 (1978), S. 583-592 
    Details
    ISSN: 1432-1106
    Keywords: Ovulation ; Hypothalamic stimulation ; Pro-oestrous rats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The experiments were designed to specifiy optimal parameters of hypothalamic electrical stimulation to induce ovulation in rats anaesthetised with pentobarbitone during the “critical period” on the afternoon of pro-oestrous. We have established that duration of stimulation in the arcuate region of the hypothalamus is of greater importance than total number of pulses delivered. The minimum period of stimulation to ensure that all rats ovulated was 45 min. However, stimulation in the arcuate region did not have to be continuous throughout this period. Indeed, three 5-min bursts at 100 Hz distributed equally through 45 min always caused ovulation whereas a continuous 15-min stimulation at the same frequency was without effect. With 30 min of continuous stimulation in the arcuate region, at frequencies ranging from 10 to 100 Hz, approximately half of the rats ovulated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235576
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