Effects of 2-bromo-alpha-ergocryptine and pimozide on growth hormone secretion in man

Bromocriptine and its use in Parkinsonism

Bromocriptine is a potent dopamine agonist which directly stimulates dopamine receptors. In the corpus striatum, this action results in alleviation of many of the signs and symptoms of parkinsonism. The effectiveness of bromocriptine may persist for at least one to two years; results of more prolonged treatment are not available. Adverse reactions are common and often severe, but safety in dosages up to 100 mg daily for one to two years has been adequately established. Bromocriptine is qualitatively and quantitatively similar to levodopa in both beneficial and adverse effect. However, because of variations in individual response, bromocriptine sometimes ameliorates the problems of prolonged levodopa therapy, i.e., declining efficacy, fluctuations in therapeutic response, and the development of disabling abnormal involuntary movements, Thus bromocriptine is a valuable adjunct in the treatment of parkinsonism.

Effect of pimozide on the cytology of the eel pituitary. I. Prolactin-secreting cells

Pimozide, a specific blocker of dopaminergic receptors, was injected for 4 to 9 days in freshwater (FW) eels or eels acclimated to sea water (SW), for 10 to 30 days. The daily dose was 100 or 200 microgram/100 g. In FW, pimozide induces a nuclear hypertrophy in the prolactin (PRL) cells of eels; these elongated cells increase in height. The amount of erythrosinophilic granules in the cytoplasm, initially reduced, increases. Plasma electrolyte values are not modified: only the plasma sodium level slightly rises with the higher dose. In SW, PRL cells appear less active. After 10 days, this hypoactivity is not yet fully evident; pimozide stimulates PRL cells without affecting electrolyte values. After 1 month in SW, PRL cells are stimulated with pimozide and a slight regranulation may occasionally occur. The response in SW is never as marked as it is in FW; a high dose is not more effective than a low one. The higher dose significantly raises Na+, Ca2+ and Cl- plasma levels. These data suggest that prolactin synthesis and release increase with pimozide. They corroborate the hypothesis of a hypothalamic inhibitory control on PRL secretion mediated through dopaminergic fibers in the eel, but other factors may also be involved in this regulation in addition to the effect of salinity.