Localization of prolactin receptor in the newt brain

Abstract

In the male newt Cynops pyrrhogaster, prolactin (PRL) acts directly on the central nervous system and induces courtship behavior. As a step to elucidate the localization of neurons on which PRL acts, we developed a polyclonal antibody against an oligopeptide having a sequence completely identical with a part of the sequence of PRL receptors (PRLRs) of two species of newts, C. pyrrhogaster and C. ensicauda, and performed an immunohistochemical study with this antibody. PRLR-immunoreactive cells were observed in the medial amygdala, anterior preoptic area, magnocellular preoptic nucleus, suprachiasmatic nucleus, nucleus of the periventricular organ, ventral hypothalamic nucleus, and choroid plexus. We also performed in situ hybridization with a (35)S-labeled newt PRLR antisense RNA probe and detected signals in the preoptic area and choroid plexus. Colocalization of both PRLR-like immunoreactivity and arginine vasotocin-like or mesotocin-like immunoreactivity was demonstrated in the magnocellular preoptic nucleus. This is the first report of PRLR localization in the amphibian brain.

Localization of three types of arginine vasotocin receptors in the brain and pituitary of the newt Cynops pyrrhogaster

“…In Triturus cristatus, the courtship-controlling center has been assumed to be located in the preoptic area (Malacarne and Giacoma 1980). We have demonstrated that the receptor for prolactin, which is a another important hormonal factor involved in the expression of courtship behavior (Toyoda et al 1996), is found in the anterior preoptic area and magnocellular preoptic nucleus (Hasunuma et al 2005). In the study reported here, we have also observed the expression of V1a-type receptor in the anterior preoptic area and magnocellular preoptic nucleus.…”

Mode of Action and Functional Significance of 7?-Hydroxypregnenolone Stimulating Locomotor Activity

“…In the choroid plexus of newts, dense PRLR immunoreactivity and PRLR mRNA signals were observed in the epithelial cells (Hasunuma et al, 2005). Thus, PRL transported from the blood into the cerebrospinal fluid via the choroid plexus receptor is considered to play an important role in the expression of locomotor activity and courtship behavior, although a possible contribution of PRL transported to the brain through retrograde blood flow by the portal system cannot be excluded as reported in mammals (Oliver et al, 1977; Porter et al, 1978).…”

Possible hormonal interaction for eliciting courtship behavior in the male newt, Cynops pyrrhogaster

“…In the newt, PRL which promotes courtship behavior is considered to be mainly of pituitary origin, as evidenced by hypophysectomized male newts ceasing to show courtship behavior and subsequent injections of PRL together with gonadotropin or androgen restoring it (Toyoda et al, 1993). Hasunuma et al (2005) demonstrated that in the newt, both immunoreactive PRL receptor and PRL receptor mRNA exist in the choroid plexus and in the neuronal cells situated closely to the third ventricle. These authors proposed that PRL is transported through the choroid plexus to the brain across the blood-cerebrospinal fluid barrier.…”

“…As regards the localization of the PRL receptors in the brain of the red-bellied newt, Hasunuma et al (2005) reported that PRL receptor-immunoreactive cells are present in the amygdala in the telencephalon and in the anterior preoptic area, magnocellular preoptic nucleus, suprachiasmatic nucleus, and periventricular nucleus in the diencephalon. Should PRL regulate the secretion of AVT in the newt, the PRL receptor-immunoreactive neurons in any of the above-mentioned regions would also be AVT-immunoreactive.…”