Abstract
Summary
Light induced constant estrous female rats were injected daily with central acting drugs that either increased or decreased brain catecholamines or serotonin or altered levels of both amines. Only the combination of L-dopa and p-chloroamphet-amine (PCA) was effective in reinitiating regular estrous cycles in the rats while still under constant light. Nine of 15 rats so treated with PCA and L-dopa in the first experiment showed at least 2 consecutive cycles, and 22 of 30 rats in a second experiment showed 3 consecutive cycles. Serum LH was observed from 10 AM to 6 PM on the day of proestrus in the 22 cycling rats of the second experiment. Rats showing LH peaks ovulated by the next day. These results suggest that constant light induces a deficiency of catecholamines and an excess of serotonin in the hypothalamus, thereby preventing normal LH release.
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