Reproductive phase‐related variations in cocaine‐ and amphetamine‐regulated transcript (CART) in the olfactory system, forebrain, and pituitary of the female catfish, Clarias batrachus (Linn.)

Abstract

The annual sexual cycle of Clarias batrachus is divisible into resting (December-January), preparatory (February-April), prespawning (May-June), spawning (July- August), and postspawning (September-November) phases. The gonosomatic indices rose steadily through the preparatory and prespawning phases, peaked in the spawning phase, and were greatly reduced during the postspawning and resting phases. A clear pattern of change was also identified in the immunocytochemical profile of the luteinizing hormone (LH) cells in the pituitary. These changes were correlated with the cocaine- and amphetamine-regulated transcript (CART)-immunoreactive system in the forebrain and pituitary. In the olfactory bulb, CART immunoreactivity in the terminal fields of the mitral cell layer, granule cells, and medial olfactory tracts gradually decreased during the resting through prespawning phases. However, it was considerably augmented during spawning (P < 0.001) and showed highest activity in the postspawning phase (P < 0.001). A different pattern was noticed in the fibers and/or neurons of the lateral part of ventral telencephalic area, the entopeduncular nucleus, and the dorsal part of the nucleus preopticus periventricularis. In these areas, intense immunoreactivity seen in preparatory phase, declined during prespawning (P < 0.01) then through spawning, and was partially augmented during the postspawning and resting phases (P < 0.05). A similar pattern was also seen in the nucleus preglomerulosus lateralis and medialis, nucleus dorsalis posterioris of thalamus, lobobulbar nucleus, and the nucleus of posterior recess. CART was transiently expressed in LH cells in the pituitary during the preparatory period. We suggest that the CART system may play a role in triggering the brain-pituitary-ovary axis at the onset of the preparatory phase.

Cocaine‐ and amphetamine‐regulated transcript peptide (CART) in the telencephalon of the catfish, Clarias gariepinus: Distribution and response to fasting, 2‐deoxy‐D‐glucose, glucose, insulin, and leptin treatments

“…While the results herein underscore a role for CARTcontaining EN neurons in the regulation of energy balance, studies based on another catfish, C. batrachus, suggest that CART neurons of the EN, and several fibers in the telencephalon, may be involved in the regulation of reproduction (Barsagade et al, 2010). To this end, the EN neurons seem to hold a strategic position.…”

“…These control procedures suggest that the immunoreactivity is specific to CART. We may note that these antibodies also cross-reacted with the CART in the brain sections of another catfish, C. batrachus, and with the neurons of arcuate nucleus of rat Barsagade et al, 2010).…”

“…The method is standardized in our laboratory Barsagade et al, 2010). CART immunoreactivity in the EN neurons was evaluated in terms of percent area occupied by the immunostained product within the predetermined areas as indicated (see Results) but the immunoreactive fibers in the given field were not considered.…”

“…The streptavidin-biotin-peroxidase and immunofluorescence methods as described previously Barsagade et al, 2010) were employed with minor modifications to localize CART in tissue sections. Briefly, the sections were washed in PBS (pH 7.45) for 15 minutes and treated with 1% BSA in PBS containing 0.3% Triton X-100.…”

Central Pathways Integrating Metabolism and Reproduction in Teleosts

“…CART is also expressed in LH cells of the catfish pituitary but only during sexual maturation period (222), suggesting its local function in the sexual maturation process. However, it should be noted that while similar expression of CART in LH cells is observed in the rat pituitary, CART inhibits the release of prolactin but not GTHs (223).…”