IMMEDIATE AND LONG-TERM EFFECTS OF 5,7-DIHYDROXYTRYPTAMINE ON RAT STRIATAL SEROTONERGIC NEURONS MEASURED USING IN-VIVO VOLTAMMETRY

The immediate and long-term effects of the selective serotonergic neur otoxin 5,7-dihydroxytryptamine (5,7-DHT) on rat striatal serotonergic neurons were examined after its intracerebroventricular administration using in vivo voltammetry. Extracellular concentration of 5-hydroxyin doles increased immediately following intracerebroventricular 5,7-DHT injection (200 mu g in 24 mu l, 18 min), peaked at 1.5-2 h, and return ed to normal by 4 h. 5,7-DHT diffused to the contralateral striatum in detectable amounts 9 to 12 min after the start of injection and retur ned to basal levels by 1.5 h. Three to 6 days after 5,7-DHT lesions, 5 -hydroxytryptophan administration produced an increase in striatal 5-h ydroxyindoles that was greater than that produced in pre-lesioned rats . This effect was maximal at 14 to 17 days post-lesion, and remained e ven after 50 days. The short-term effect of 5,7-DHT may be attributabl e to increased serotonin release, inhibition of uptake, or monoamine o xidase inhibition. The long-term effect of 5,7-DHT lesions may attribu table to increased synthesis of serotonin or decreased reuptake in rem aining serotonergic neurons.