BACKGROUND: @entity935 (DA) neurons in the anteroventral periventricular nucleus (AVPV) in the preoptic area (POA) of mammals express @entity172 receptors, regulate luteinizing hormone (LH) secretion, and show distinct sexual dimorphism. In teleosts, hypophysiotropic DA neurons of the nucleus preopticus periventricularis (NPP), located in the anteroventral POA, express @entity172 receptors, innervate LH cells, and emerged as a neuroanatomical substrate for inhibiting LH cells. Interestingly, the NPP and AVPV seem to share several similarities. Whether DAergic neurons in the NPP show sexual dimorphism is, however, not known. Based on the proposed homology to AVPV and previous studies showing greater @entity4149 hydroxylase (TH) mRNA and enzyme activity levels in the brain of female catfish, we hypothesize that females have greater number of DAergic neurons in the NPP and correspondingly more TH-immunoreactive fiber innervation of the pituitary. METHODS: Adult, male and female Clarias batrachus collected during the prespawning phase of their reproductive cycle were used. Fish were anesthetized and perfused transcardially with @entity4613 -buffered saline (pH 7.4) and 4  % @entity1604 in @entity4613 buffer. Sections through the rostro-caudal extent of the POA and pituitary were processed for TH immunofluorescence. Using double immunofluorescence, the association between TH-immunoreactive fibers and LH cells in the pituitary was explored. Sections were analyzed using semiquantitative analysis. RESULTS: NPP in POA of C. batrachus has two distinct subdivisions, viz, anterior ( @entity8224 ) and posterior (NPPp), and TH neurons were observed in both the subdivisions. Compared to that in the males, a significantly higher (P   <   0.05) number of TH neurons was consistently observed in the @entity8224 of females. TH neurons in NPPp, however, showed no difference in the number or immunoreactivity. Since DA neurons in @entity8224 are hypophysiotropic, we compared TH-fiber innervation of the pituitary in both sexes. Compared to males, proximal pars distalis and LH cells in this region of the pituitary in females were densely innervated by TH fibers. CONCLUSIONS: Neurons of @entity8224 and their innervation to the pituitary seem to be a distinct sexually dimorphic DAergic system in C. batrachus. The DAergic system may serve as a component of the neural mechanisms controlling the sexually dimorphic LH surge in teleosts. Given the similarities shared by @entity8224 and AVPV, homology between these two nuclei is suggested.

Sexual dimorphism in the hypophysiotropic XXXX hydroxylase-positive neurons in the preoptic area of the teleost, Clarias batrachus.

@entity172 :: ('MESH:D004967', 'Chemical') :: ['estrogen'] @entity8224 :: ('4878', 'Gene') :: ['NPPa'] @entity935 :: ('MESH:D004298', 'Chemical') :: ['Dopamine'] @entity4613 :: ('D010710', 'Chemical') :: ['phosphate'] @entity1604 :: ('MESH:C003043', 'Chemical') :: ['paraformaldehyde'] @entity4149 :: ('D014443', 'Chemical') :: ['tyrosine']
@entity4149 :: (D014443,Chemical) :: ['tyrosine']
