Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline), is a recently identified endogenous prolactin (PRL) releasing factor. Salsolinol (SALS) seems to be a selective and potent stimulator of PRL secretion both in vivo and in vitro. 1-Methyl dihydroisoquinoline (1MeDIQ) is an antagonist of salsolinol induced prolactin release and causes increase in plasma norepinephrine (NE) level. SALS decreased the peripheral tissue dopamine (DA) level dose dependently, consequently increased the NE/DA ratio, indicating reduced release of newly formed NE from sympathetic terminals. These effects can be antagonized by 1MeDIQ pretreatment. The aim of our study was to investigate the effect of medullectomy (MEDX), adrenalectomy (ADX) and hypophysectomy (HYPOX) on the interaction of SALS and 1MeDIQ on the catecholamine concentration of the selected sympatheticly innervated peripheral tissues (spleen, atrium, etc). We used HPLC-EC method for measurement of NE and DA concentrations. In ADX as well as in MEDX rats, SALS was able to reduce DA level and increase the NE/DA ratio that could be prevented by 1MeDIQ pretreatment. Therefore the presence of adrenal gland is not required for the reduction of peripheral sympathetic activity induced by SALS. Investigating the possible role of pituitary hormones on the peripheral sympathetic system, the effect of SALS has been tested in HYPOX rats. We have found that the effect of SALS on peripheral sympathetic terminals is not affected by HYPOX, conseqently pituitary hormones do not play any role in the catecholamine depleting activity of SALS. The possible physiological significance of these observations need further clarifications.
This work was supported by the National Scientific Research Fund (OTKA T-04337) and the Ministry of Health (ETT 177/2006) to GMN.