Stretch sensory ovarian‐preoptic pathway in the teleost, Clarias batrachus (Linn.): Transection studies

Abstract

Application of intraovarian pressure (IOP), coupled with placement of discrete lesions, has been employed to study the organization of the pressure excitable ovarian-preoptic pathway in a teleost, Clarias batrachus. While bilateral administration of the IOP triggered stimulatory changes in the nucleus preopticus (NPO), they were abolished if the IOP administration was preceded by the bilateral transection at the level of 1) foramen magnum, 2) spinal cord a t the level of 13th vertebra, 3) dorsal spinal nerve roots between the levels of 13th and 21st vertebrae, and 4) at the junction between the common oviduct and the body wall. On the other hand, bilateral sectioning of the anterior mesovarium, the vagi, or the spinal cord a t the level of 21st vertebra had no effect. Unilateral administration of the IOP triggered bilateral changes in the NPO. It seems that the stretch receptors in the ovarian wall give rise to processes that proceed along the margin of the oviduct and enter the spinal cord via the dorsal nerve roots between 13th and 21st vertebrae. Thereafter, the pathway seems to ascend over the spinal cord and impinge on the ipsilateral as well as contralateral pathways are important because they provide the means to 1) assess the reproductive status of the ovaries, 2) convey the neural feed-back signals, independent of the hormonal system, and 3) influence the neuroendocrine activity in the hypothalamus.In the present investigation, an attempt has been made to study the gross organization of the stretch excitable pathway that presumably originates in the ovarian wall and projects to the NPO. Study of the NPO following placement of transections across the pathway from the ovary en route to the brain, coupled with application of stretch signals to the ovary, offered convenient means of determining the course of the pathway. the NPO, following any particular transection, indicated the occurrence of the pathway via the transected route. This approach was found suitable for several reasons. First, following the application of IOP of predetermined magnitude, the NPO responds in a characteristic manner. The changes could be detected light microscopically using histological and immunocytochemical procedures; there was a statistically highly significant hypertrophy of the cells and cell nuclei, accompanied by synthetic and secretory changes in the somata (Subhedar et al., '87). Second, since the ovary is a visceral organ, the transections could be placed at discrete sites along the ascending route. Third, the characteristic response by the NPO was independent of the other factors such as the season or the status of the ovarian maturity (Deshmukh, '92). MATERIALS AND METHODSAnimals Adult female catfish Clarias batrachus (Linn.) weighing between 70 and 90 g were used in the present study. Experiments were performed in the months of February and March coinciding with the

Immunohistochemical localization of cocaine‐ and amphetamine‐regulated transcript peptide in the brain of the catfish, Clarias batrachus (Linn.)

“…This region of the hypothalamus is homologous to the paraventricular nucleus (PVN) in the rat brain, which is intensely innervated by CARTp fibers Sarkar et al, 2004). The NPO neurons of C. batrachus are known to serve as a source of neurohypophysial hormones and corticotrophin releasing factor (CRF) Deshmukh and Subhedar, 1993) and also project to the pituitary gland (Rama Krishna and Subhedar, 1989). It would be interesting to explore the interaction of CARTp with the neurons of the NPO, and its role in NPO-associated functions like osmoregulation, adreno-corticotropic hormone (ACTH)-interrenal axis, and stress.…”