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Mono- and Indolamines and Control of LH Secretion
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1970
Year
Protein SecretionNeuropeptidesLh ReleaseNeurotransmitterPsychopharmacologyPharmacotherapyExperimental PharmacologySocial SciencesMolecular PharmacologyCardiac PunctureLh SecretionAnesthetic PharmacologyAnimal PhysiologyMolecular PhysiologyBiochemistrySodium HomeostasisBehavioural PharmacologyBehavioral PharmacologyNeuropharmacologyNervous SystemEndocrinologyPharmacologyDopamineNeurophysiologyPlasma LhPhysiologyElectrophysiologyAnesthesiaMedicineAnesthesiology
To determine the effect of biogenic amines on LH release in rats, blood samples were drawn by cardiac puncture in etheranesthetized animals bearing chronic cannulae in the third ventricle (3rd V) immediately before and 15 min after intraventricular injection of various drugs. In the interim between removal of the 2 blood samples the rats recovered from anesthesia. Plasma LH was measured by radioimmunoassay. Serotonin (5-HT) did not alter plasma LH levels significantly at any stage of 4-day estrous cycles. Norepinephrine (NE) also failed to produce over-all significant changes in plasma LH although there were some positive responses. Dopamine (DA) raised LH to levels as high as 8- or 10-fold above controls (p<.01) in rats on the 2nd day of diestrus (D2) or in proestrus (P). DA proved to be less effective in Dl or estrus (E). In normal males DA raised plasma LH in 5 out of 9 animals (p<.02), whereas NE was ineffective. The effect of DA in D2 and P rats could be blocked by simultaneous 3rd V injection of 30 μg phenoxybenzamine, but remained unaltered after the same dose of pronethalol. In spayed females NE or DA produced variable results independent of base line LH levels; however, 5-HT significantly (p<.01) decreased LH release in these animals. Estrogen progesterone-blocked castrated female rats responded with up to 10-fold increases (p<.0l) in plasma LH following 3rd V injection of DA, whereas NE produced only slight increases in 5 out of 9 rats. Monitoring an individual rat of this type by drawing blood from a carotid artery catheter at 3–7 min intervals revealed an 8-fold increase of plasma LH 7 min after intraventricular injection of DA. Saline (0.9 %) did not produce an effect on LH release under any of the described conditions. The results provide in vivo evidence for the role of DA in LH release, probably as transmitter for the release of LRF, as shown by the authors in earlier in vitro experiments. A possible inhibitory role of 5-HT is also suggested. (Endocrinology86: 1127, 1970)