Behavioural, biochemical and electrophysiological studies on the motor depressant and stimulant effects of bromocriptine

Naunyn-Schmiedeberg's Archives of Pharmacology
D M JacksonS B Ross

Abstract

Bromocriptine (BRC) produced a biphasic behavioural effect in mice; an early depressant phase which lasted for about 1 h and a later stimulant phase which lasted from about 1 to 5 h. The stimulation was blocked with SCH23390. Both phases of activity were accompanied by marked striatal DA autoreceptor effects as indicated by reductions in dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels and by a reduction in the accumulation of DOPA (after inhibition of nigrostriatal DA nerve firing and DOPA decarboxylase). However, while the autoreceptor effects were still evident during the behavioural stimulant phase, there was a gradual rise in DOPAC and HVA from 1 to 4 h after injection, indicating a gradually increasing DA turnover. We were unable, using a variety of behavioural and biochemical paradigms, to demonstrate any change in DA autoreceptor sensitivity after one dose of BRC. In electrophysiological studies, however, it was found that prior exposure of rats to one dose of BRC rendered them subsensitive to the rate-inhibiting effects of a second dose of BRC, as measured in anaesthetized animals using extracellular single cell recordings of identified DA neurons in the substantia nigra pars compacta. It is conclu...Continue Reading

Citations

Jan 1, 1994·Pharmacology & Therapeutics·D M Jackson, A Westlind-Danielsson
Jun 21, 2005·Alcohol·Julie BroadbentSharon A Koonse
Jan 1, 1993·Journal of Neural Transmission. Parkinson's Disease and Dementia Section·T BrannanM D Yahr

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