Androgen Effects on Tyrosine Hydroxylase Cells in the Northern Leopard Frog, <i>Rana pipiens</i>

Abstract

The interaction between gonadal steroids and dopamine neurons has been examined extensively in rodent model systems. However, there have been few investigations examining the functional relation between gonadal steroids and dopaminergic systems in nonmammalian taxa, and none in amphibians. We examined the effects of testosterone (T) and dihydrotestosterone (DHT) on changes in tyrosine hydroxylase immunoreactive (TH-ir) neuron number in the fore- and midbrain of male Rana pipiens, the Northern leopard frog, using a whole-mount immunohistochemical procedure. Gonadectomized males had significantly fewer TH-ir neurons in the medial preoptic area (POA), suprachiasmatic nucleus (SCN), and the caudal hypothalamus/posterior tubercular region (HY/TP) compared with T-implanted males. A follow-up study demonstrated that T- and DHT-implanted males had similar numbers of TH-ir neurons in these three regions compared with intact males and that all three of these groups possessed significantly more TH-ir neurons compared with gonadectomized males. These results suggest that circulating sex steroids have a significant impact on the activity of dopaminergic neurons in male R. pipiens. Although the function of these specific dopaminergic neurons is not yet known, the POA, SCN, and TP/DH are known to be integral brain regions underlying the neural control of reproductive behavior in frogs. These results suggest that dopamine may be important in controlling the behavior or neuroendocrine mechanisms of reproduction in these animals and that dopaminergic activity in these areas is regulated by gonadal steroids.

Characterization of the Dopamine System in the Brain of the Túngara Frog, <i>Physalaemus pustulosus</i>

“…After washing 5 times for 3 min each with wash buffer, the membrane was exposed to HRP substrate (Immobilon Western, Millipore) and exposed to film for 2 min. Using the TH antibody, a single band was visualized at the predicted size of 59-61 kDa, the appropriate size of anuran TH [Chu and Wilczynski, 2002]. Using the DARPP-32 antibody, a single band was visualized at the predicted size of 20.1 kDa, putatively representing DARPP-32 ( fig.…”

“…Marín and colleagues [1995] have described the mesolimbic reward system in anurans as dopaminergic projections originating from the posterior tuberculum to the nucleus accumbens. Dopaminergic neurons in the posterior tuberculum are required for phonotaxis behavior in female grey tree frogs [Endepols et al, 2004] and vary in number with sex and gonadal hormone levels in Northern leopard frogs [Chu and Wilczynski, 2002;Wilczynski et al, 2003].…”

Immunohistochemical Analysis of Monoaminergic Neurons in the Brain of the Common Marmoset, Callithrix jacchus

“…Antiserum against TH (MAB318, Chemicon Co. Ltd.) has been described [2,34,37], and species specificities of this antiserum have been confirmed in humans, rats, monkeys, frogs and voles. In addition, a control test was performed in which PBS was used in place of primary antibody.…”

Tyrosine hydroxylase expression is affected by sexual vigor and social environment in male Cnemidophorus inornatus

“…1989; Sanghera et al, 1991;Chu and Wilczynski, 2002;Wilczynski et al, 2003). Furthermore, adrenal steroid hormones influence TH expression in tuberoinfundibular neurons as well as in neurons of the VTA in rats (Van Loon et al, 1977;Ortiz et al, 1995).…”

“…For example, males housed with females have lower androgen and higher corticosterone concentrations than males housed in isolation (Lindzey and Crews, 1988b). Because gonadal and adrenal steroid hormones affect TH expression in mammals (Sanghera et al, 1991;Watanabe et al, 1995;Filipenko et al, 2001) and amphibians (Chu and Wilczynski, 2002), it is possible that heterosexual housing can alter the dopaminergic system in whiptail lizards.…”