Expression of androgen receptor mRNA in the brain of Gekko gecko: Implications for understanding the role of androgens in controlling auditory and vocal processes

Abstract

The neuroanatomical distribution of androgen receptor (AR) mRNA-containing cells in the brain of a vocal lizard, Gekko gecko, was mapped using in situ hybridization. Particular attention was given to auditory and vocal nuclei. Within the auditory system, the cochlear nuclei, the central nucleus of the torus semicircularis, the nucleus medialis, and the medial region of the dorsal ventricular ridge contained moderate numbers of labeled neurons. Neurons labeled with the AR probe were located in many nuclei related to vocalization. Within the hindbrain, the mesencephalic nucleus of the trigeminal nerve, the vagal part of the nucleus ambiguus, and the dosal motor nucleus of the vagus nerve contained many neurons that exhibited strong expression of AR mRNA. Neurons located in the peripheral nucleus of the torus in the mesencephalon exhibited moderate levels of hybridization. Intense AR mRNA expression was also observed in neurons within two other areas that may be involved in vocalization, the medial preoptic area and the hypoglossal nucleus. The strongest mRNA signals identified in this study were found in cells of the pallium, hypothalamus, and inferior nucleus of the raphe. The expression patterns of AR mRNA in the auditory and vocal control nuclei of G. gecko suggest that neurons involved in acoustic communication in this species, and perhaps related species, are susceptible to regulation by androgens during the breeding season. The significance of these results for understanding the evolution of reptilian vocal communication is discussed.

Distribution of sex steroid hormone receptors in the brain of an African cichlid fish, Astatotilapia burtoni

“…The nodes of this network include the preoptic area (POA), anterior hypothalamus, ventromedial hypothalamus, medial amygdala (MeAMY) and bed nucleus of the stria terminalis (BNST), periaqueductal gray, and the lateral septum (LS). These regions contain steroid hormone receptors in every vertebrate class studied including reptiles (Young et al, 1994;Moga et al, 2000;Tang et al, 2001;Rosen et al, 2002), amphibians (Meglio et al, 1987;Guerriero et al, 2005), birds (Sterling et al, 1987;Balthazart et al, 1998;Foidart, 1999;Belle and Lea, 2001), and mammals (Kato et al, 1994;Osterlund et al, 1998;Murphy et al, 1999;Roselli et al, 2001;Zhang et al, 2002;Holmes et al, 2008). The only exceptions seem to be in the periaqueductal gray, where ER is absent in reptiles and PR is absent in birds.…”

“…Regions that receive input from this dopaminergic system include the basolateral amygdala, hippocampus, nucleus accumbens, ventral pallidum, striatum, BNST, and the lateral septum. Most of these brain nuclei contain steroid hormone receptors in reptiles (Young et al, 1994;Moga et al, 2000;Tang et al, 2001), amphibians (di Meglio et al, 1987;Guerriero et al, 2005), birds (Sterling et al, 1987;Balthazart et al, 1998;Foidart et al, 1999;Belle and Lea, 2001), and mammals (Kato et al, 1994;Osterlund et al, 1998;Murphy et al, 1999;Zhang et al, 2002;Holmes et al, 2008). However, there are some exceptions, as PR is not present (or has not been reported) within the avian amygdaloid complex or in the VTA; ER is not present (or has not been reported) within the nucleus accumbens, striatum, VTA, or amygdaloid complex of reptiles, and AR is not present (or has not been reported) in the VTA of reptiles or within the striatum of mammals.…”

Development of N‐methyl‐D‐aspartate receptor subunits in avian auditory brainstem

“…The slides were washed again in 1ϫ SSC and 0.1ϫ SSC for 15 minutes at 42°C. Subsequent procedures for digoxigenin-labeled probes hybridization after SSC washing followed a standard method (Tang et al, 2001). For 35 S-labeled probe hybridization, the slides were air dried and dipped in NTB2 emulsion diluted 1:1 in water.…”

Development of NMDA R1 expression in chicken auditory brainstem

“…The slides were washed again in 1× SSC and 0.1× SSC for 15 minutes at 42°C. Subsequent procedures for digoxigenin-labeled probes hybridization after SSC washing followed a standard method (Tang et al, 2001). For 35 S-labeled probe hybridization, the slides were air dried and dipped in NTB2 emulsion diluted 1:1 in water.…”