Faculty Bibliography

The alteration in circulating levels of PRL, GH, TSH, and cortisol was studied after the oral administration of muscimol (3-hydroxy-5-aminomethylisoxazole) to human subjects with Huntington's disease (n = 4) and chronic schizophrenia (n = 5). PRL levels rose significantly in a dose-dependent fashion within a 120-min time interval. GH rose significantly but modestly over the same time interval, whereas TSH and cortisol levels remained unchanged. Since muscimol is thought to be a potent and specific gamma-aminobutyric acid agonist, these data indicate that gamma-aminobutyric acid-mediated neural transmission may function to stimulate the release of plasma PRL and GH in human subjects.

The response of Parkinsonism to three ergot derivatives which modify dopaminergic transmission was studied. CF 25-397 behaved more as an antagonist than an agonist. Lergotrile was an agonist with therapeutic properties marred by prominent hepatotoxicity. Bromocriptine is an effective anti-Parkinsonian agent, particularly useful in patients with prominent dyskinesia or "on-off" reactions to levodopa; in most patients optimal results have been obtained by combining from 40 to 90 mg of bromocriptine daily with approximately 60% of the previous maximal dose of levodopa. Unfortunately, only some 50% of patients tolerate long-term bromocriptine therapy, but all adverse reactions have been dose dependent and reversible.

92 patients with parkinsonism have been treated with bromocriptine for up to 30 months. 48 continue to receive bromocriptine with benefit; of these, 35 take bromocriptine (mean dose 53 mg daily) in combination with levodopa and 13 take bromocriptine (mean dose 45 mg daily) without levodopa. In those who were originally on levodopa, addition of bromocriptine allowed a mean 41% reduction in the dose of levodopa; the largest group of patients to benefit from bromocriptine entered the study because of excessive dyskinesia or "on-off" phenomena induced by levodopa. In 40 patients bromocriptine was stopped because of adverse reactions, absence of therapeutic response, or non-compliance with the protocol. The main problems were psychiatric disturbance (8 patients) and erythromelalgia (7 patients); these effects tended to occur late (mean 6 months and 10 months, respectively) and with high dosage (mean 66 mg and 115 mg daily). Other frequent adverse effects were dizziness and nausea; these began considerably earlier (at 2 months and 1 month) and with much lower dosage (31 mg and 12 mg daily). 4 patients died, for reasons apparently unrelated to therapy.