Autoradiographic localization of hormone‐concentrating cells in the brain of an amphibian, Xenopus laevis. II. Estradiol

Abstract

Autoradiographic techniques for light microscopic examination of sex steroid retention were applied to the brains of male and female Xenopus laevis, and anuran amphibian, after 3H-estradiol administration. Estrogen was concentrated by cells in three telencephalic areas (the ventral striatum, the ventral-lateral septum and the amygdala), the anterior preoptic area, the ventral thalamus, the ventral infundibular nucleus, and in the torus semicircularis. The anterior preoptic area and the ventral infundibular nucleus contained the greatest number of labelled cells. The topography of estrogen-concentrating cells was the same in male and female brains. This fact and comparisons of 3H-estradiol with 3H-testosterone retention in Xenopus suggest that the sex steroid itself, and not the genetic sex of Xenopus determines the pattern of uptake by cells in the brain. The distribution of hormone-concentrating cells in Xenopus has many similarities to that found in birds and mammals. Preoptic, hypothalamic (tuberal), limbic forebrain and specific mesencephalic sites in all these forms contain labelled cells following radioactive sex steroid administration. Findings in Xenopus add to the argument for a phylogenetically stable system of hormone-concentrating nerve cells in limbic, hypothalamic and mesencephalic structures.

Functional Mapping of the Auditory Midbrain during Mate Call Reception

“…In addition to its auditory input, the laminar nucleus receives modulatory input that is heavily dominated by forebrain limbic areas, such as the preoptic area and hypothalamus (Endepols and Walkowiak, 1999). Furthermore, steroid binding sites are present in this toral subdivision Morrell et al, 1975;Endepols et al, 2000). In light of this limbic and endocrine modulation, we propose that egr-1 responses of laminar nucleus neurons may be influenced by the biological meaning of signals.…”

Estrogen and Laryngeal Synaptic Strength in <i>Xenopus laevis:</i> Opposite Effects of Acute and Chronic Exposure

“…Alternatively, the primary target for estrogen action on the vocal system may be central rather than peripheral. For example, estrogen may affect vocalization by acting on its neural targets [19]; effects on laryngeal synapses described here would then be incidental to the major, central activity of this steroid hormone.…”

“…These observations suggest an action of estrogen on the laryngeal motor neuron. However, this cell does not appear to express estrogen or progesterone receptors either in Xenopus or in mammals [19, 20]though androgen receptors are expressed at high levels [21, 22]. Thus genomically mediated effects on the laryngeal motor neuron are probably transynaptic in nature, either anterograde influences from neurons in ventral diencephalon, thalamus and auditory midbrain [22, 23]or retrograde influences from laryngeal muscle which does express estrogen receptor mRNA [Wu, Tobias, Kelley, unpubl.…”

Androgen receptor levels in cranial nerve nuclei and tongue muscles in rats

“…Since the cochlear nuclei have the lowest androgen binding capacity when compared to brain stem motor nuclei or the forebrain limbic regions (11.6 fmol/mg protein) and cerebral cortex (4.7 fmol/mg protein) reported previously (McGinnis et al, 1983) the duration of the exposure time routinely utilized for radioautography may not be long enough to reveal uptake of the labeled steroid. To our knowledge, steroid-concentrating neurons in the auditory system have been reported only in frogs (Kelley, 1980;Morrell et al, 1975). Since neurons in the auditory system in frogs accumulate both DHT and estrogen, we sought to measure estrogen binding sites in the rat cochlear nuclei.…”

“…Recently, it has been demonstrated that gonadal steroid-sensitive neurons are more widely spread. Radioautographic studies in several vertebrate classes have revealed that motor neurons in nuclei of cranial and spinal nerves, as well as neurons of sensory projection areas in the brain stem and spinal cord, concentrate significant amounts of radioactivity following in viva administration of 3H-steroids (Arnold et al, 1976;Breedlove and Arnold, 1980;Commins and Yahr, 1985;Keefer et al, 1973;Kelley, 1980;Kelley et al, 1975;Morrell et al, 1975Morrell et al, , 1982Sar and Stumpf, 1977;Sheridan and Weaker, 198 1, 1982). While receptors for gonadal steroids in the forebrain have been measured and characterized, those in the brain stem and spinal cord have not been studied quantitatively.…”