In the microiontophoretic study 5 barrelled electrodes were positioned in the dorsal raphe nucleus. The recording and balance barrels were filled with 2 M NaCl containing 2 pontamine sky blue, drug barrels regular firing rate . DOI was administered systemically . 2.4. Dialysis All measurements were made in the frontal cortex using probes of similar design to those previously described . Probes were perfused with artificial CSF : NaCl 125, NaHCO, 27, KC1 2.5, NaH,PO, 0.5, NaHPO, 1.2, NaSO, 0.5, MgCl, 6H ,O 1, CaCl, 1, glucose 5, pH 7.41 at a rate of 1 min. 5 HT in 20 min packed with 3 pm Hypersil. Mobile phase : NaH,PO, 150, EDTA 0.1, sodium octydyl sulphonic acid 0.5, methanol 15 , pH 3.8 was pumped through the column at a flow rate of 0.25 ml min. The amines were detected electrochemically using a glassy carbon working electrode maintz.ined at a potential of 0.85 V. Basal extracellular :rilT values were calculated using the mean of the four samples collected prior to drug or saline administra,?.?n. The results are expressed as percentage change f;om the basal value.
The mean basal values for each experiment are stated in the figure legends. DO1 was administered i.v. at a dose Proteasome inhibitor of 100 pg kg i.v. or locally either in the frontal cortex or in the dorsal raphe . In some experiments the 5 HT, antagonist, ketanserin to the injection of DOI. 3. Results 3.1. Systemic administration DO1 produced a marked reduction of dorsal raphe 5 HT neuronal Firing rate as previously shown while DOI caused complete inhibition of firing which lasted for 55 f 8.4 min . The inhibition produced had a very rapid onset and offset of action. The reduction in firing rate produced by DO1 could not be blocked by prior administration of either ketanserin WI0 pg kg i.v a 5 HTz antagonist , the 5 HT, 5 HT antagonist, ritanserin , or the putative SHT antagonist, pindolol . The administration of ketanserin fig. 4A , ritanserin f.1 mg kg i.p.1 , or pindolol induced decrease in frontal cortical extracellular 5 HT concentration. 3.2.
Local administration Local administration of DO1 into the dorsal raphe ncleus produced a mTOR inhibitors kinase inhibitor complete cessation of 5 HT neurostal firing which persisted for 60 I 6 min, n 8 rats. Like the effects observed with systemic administration the onset and offset of action was very rapid. Administration of DOI directly into the frontal cortex did not significantly alter the concentration of frontal cortical extracellular 5 HT over the dose range used . However, intra raphe administration of DO1 decreased extracellular 5 HT concentration in the frontal cortex . ejection of S OH DP.4T . Microionication of DO1 decreased dorsal raphe IXUfig. 7A in all the cells inhibited by t? firing rate of 5 . neurones in the dorsal raphc dccrtxsrd rapidly on the tjection of DOI and this decrease was sustained during the c ion period.