The effect of apomorphine on serotonin neurons in dorsal raphe nucleus and catecholamine nerve terminals in paraventricular hypothalamic nucleus. Histofluorescence studies.

Histofluorescent method was employed to study the intensity of serotonin (5-HT) fluorescence in nucleus raphe dorsalis (DR) and catecholamine (CA) fluorescence in nucleus paraventricularis hypothalami (PVH). Apomorphine (APO, 20 mg/kg) induced, after 30 min, the increase in intensity of 5-HT fluorescence in DR and CA fluorescence in PVH. This increase was prevented by the previous dopamine receptor blockade by spiroperidol (2 mg/kg), administered 1 hr prior to APO. After alpha-methyl-tyrosine (alpha-MT) (2 X 400 mg/kg)-induced decrease in CA level, simultaneous intensification in 5-HT fluorescence was observed in DR. APO administered to those rats decreased the intensity of 5-HT fluorescence in DR, down to the level observed in the controls. This decrease in fluorescence was also prevented by pretreatment with spiroperidol. p-Chlorophenylalanine (PCPA)-induced inhibition in 5-HT synthesis decreased the intensity of 5-HT fluorescence and this decrease was considerably intensified by APO. The obtained results support the following concepts: 1) the effect of apomorphine on 5-HT in DR and on CA in PVH seems, to be indirect, namely through dopamine receptor stimulation, 2) the changes in 5-HT fluorescence in DR are probably connected with the acceleration in this amine turnover.