At Imphal (24 degrees 44' N) testes of lal munia, Estrilda amandava, began in June/July, peaked in September/ October, and thereafter declined to a minimum in December/January. Daily im treatments of 2.5-10 mg/kg/ bird/30 days of
naloxone during progressive phase suppressed testicular growth, but without effects during quiescent, peak, and regression phases. Daily
morphine (5 mg/kg/bird) during progressive and peak phases stimulated testicular growth, but without effects during quiescent and regression phases. Daily
morphine (10 mg/kg/bird) during progressive phase stimulated the testes, an effect reversed by daily im treatments of an equivalent dose of
naloxone. Seasonal changes in
body weight closely correlated with testicular size. Daily im
naloxone (5 and 10 mg/kg/bird/30 days) during progressive phase inhibited the increased
body weight, but had no effects during quiescent, peak, and regression phases.
Morphine (5 mg/kg/bird/day) during progressive and peak phases increased
body weight, but had no effects during quiescent and regression phases.
Morphine (10 mg/kg/bird/day) during progressive phase increased
body weight, an effect which was reversed by equivalent dose of
naloxone. Plumage color increased progressively between May and August/September, was maintained during October, and thereafter declined to reach dull-brown henny feathers by December. Daily im
naloxone (2.5-10 mg/kg/bird/30 days) regardless of the reproductive states did not affect plumage color cycle.
Morphine (5 mg/kg/ bird/day) accelerated plumage pigmentation between June and August, but had no effect during progressive or peak phases. Postnuptial decline in plumage color was inhibited by
morphine (5 and 10 mg/kg/bird/day) and
naloxone failed to reverse this effect. It is concluded that in the lal munia, endogenous
opioid peptides are important constituents of the neuroendocrine mechanisms that influence development of the testes and
body weight.