Dimorphic distribution of progestins and cortisol in the brain of Indian stinging catfish Heteropneustes fossilis (Bloch) during different reproductive phases

Abstract

In the brain, steroids are synthesized de novo from cholesterol through mechanisms which are not dependent on peripheral steroidogenic glands. These steroids, which are termed as neurosteroids accumulate within brain of several vertebrates including various teleost species. Distribution of steroids remain conserved after removal of peripheral steroids. Still a comprehensive study on the distribution of neurosteroids is lacking in the seasonal breeding teleosts. In the present study, our objective was to measure progestins (pregnenolone, progesterone, and 17-OH-progesterone) and cortisol in brain of male and female Asian stinging catfish Heteropnuestes fossilis, throughout their reproductive phases, using specific ELISA kits. Catfish H. fossilis is a seasonal breeder which serve as an excellent model to investigate physiological responses of neurosteroids and their regulatory mechanism. Our study showed that there was significant differential distribution of pregnenolone, progesterone, 17-OH-progesterone and cortisol levels with respect to season and breeding phases of the catfish. Progestins and cortisol levels are present in both male and female and varied differentially in a phase dependent manner. Among all progestins, value of pregnenolone was maximum followed by progesterone, cortisol and 17-OH-P4. The study suggested that seasonal changes in the progestins and cortisol of catfish brain may be independent of peripheral steroidogenic gland and might be important in inducing behaviour or morphological changes associated with breeding phases for regulation of reproduction.