Heterogeneous distribution of D1, D2 and D5 receptor mRNAs in monkey striatum

The primate striatum has a compartmental organization reflected both in the topography of its afferent projections and in the segregation of its morphologically similar but neurochemically distinct efferent neurons. Discretely projecting mesostriatal neurons release dopamine (DA) which modulates the responses of striatal neurons to other afferent inputs. Multiple DA receptor (DAR) subtypes have been cloned and characterized and mapping their cellular expression is crucial for understanding the influence of DA on striatal function. We report the distribution of mRNAs for D1, D2 and D5 DAR subtypes (D2R, D2R and D5R) in the striatum of cynomolgus monkeys (Macaca fascicularis) studied by in situ hybridization histochemistry (ISH) using monkey-specific cRNA probes. Adjacent sections were stained for calbindin immunoreactivity to distinguish striosomal and matrix compartments for comparison with the patterns obtained with ISH. In the caudate nucleus, D1R mRNA was concentrated in calbindin-poor striosomes where dense grain clusters were seen overlying the majority of medium-sized neurons (diameter approximately 15 microns). D1R mRNA localization was relatively homogeneous in the putamen. By contrast, the distributions of D2R and D5R mRNAs showed no clear preference for the striosomal or matrix compartments of either caudate nucleus or putamen. In the ventral striatum (nucleus accumbens, olfactory tubercle and ventral portions of caudate nucleus and putamen), expression of D1R and D2R mRNA was sparse relative to dorsal striatum, while D5R mRNA expression was roughly equal in ventral and dorsal striatum. Circumscribed zones of hybridization associated with islands of tightly packed small cells occurred with all three DAR mRNA subtypes in the ventral striatum.(ABSTRACT TRUNCATED AT 250 WORDS)

Cloning and characterization of the human GnRH receptor

A cDNA encoding the human GnRH receptor (GnRHR) has been cloned and functionally expressed in both Xenopus oocytes and COS-1 cells. The 2160 bp cDNA encodes a 328 amino acid protein with a predicted amino acid sequence that is 90% identical to that of the mouse GnRHR (Tsutsumi et al. (1992) Mol. Endocrinol. 6, 1163-1169). Injection of synthetic RNA transcript into oocytes led to the development of a depolarizing response to agonists when assayed by voltage-clamp electrophysiology. Consistent with the expression of a mammalian GnRHR, the response was blocked by GnRH antagonists. Following expression of the human GnRHR in COS-1 cells, agonists and an antagonist displaced [125I]GnRH agonist from membrane isolates with nanomolar range dissociation constants similar to those described for displacement from human pituitary membranes. Transfected COS-1 cells manifested a GnRH-stimulated increase in phosphoinositol turnover, with an EC50 of approximately 3 nM, which was inhibited by GnRH antagonists. Northern blot analysis revealed a single band of approximately 4.7 kb expressed in human pituitary which was not detected in testis. The predicted structure of the human GnRHR is similar to that previously reported for the mouse receptor. Although the mammalian GnRHR is a seven transmembrane domain receptor, it differs from other G-protein coupled receptors in several respects, most notably the lack of a cytoplasmic C-terminal domain. The present study demonstrates that the cDNA isolated encodes the human GnRHR and suggests that several unique features conserved among mammalian GnRHRs may be essential for receptor function and/or regulatory control.

Localization of multiple dopamine receptor subtype mRNAs in human and monkey motor cortex and striatum

Dopamine plays a critical role in motor and cognitive function through actions mediated by specific receptors, multiple subtypes of which have recently been identified. The distribution of mRNAs encoding D1, D2 and D5 receptors in the motor cortex of humans and in the motor cortex and striatum of macaque monkeys was examined using in situ hybridization. In motor cortices from both primate species, hybridization to each receptor probe resulted in numerous labeled cells throughout layers II-VI. In contrast to neocortex, in monkey striatum only the D1 and D2 receptor probes showed significant hybridization. Thus, not only does primate neocortex possess a broader representation of the dopamine receptor subtype mRNAs examined in comparison with striatum, but the unexpected presence and widespread distribution of D2 and D5 receptor mRNAs in cortex suggests that, along with D1 receptors, D2 and D5 receptors play a crucial role in the dopaminergic modulation of cognition and motor behavior, and in dopamine dysfunction associated with neuropsychiatric disorders.