The effects of an intraperitoneal (i.p.) injection of different doses of sildenafil, a cyclic guanosin monophosphate (cGMP) specific phosphodiesterase type 5 (PDE 5) inhibitor, on memory retention of young (2-month-old) and middle aged (12-month-old) male Wistar rats were investigated. Passive avoidance behaviour was studied in a one trial learning, step - through type, passive avoidance task utilizing the natural preference of rats for a dark environment. In each category (young or middle-aged) different groups of rats received vehicle or sildenafil (1, 3, 10, 20 mg*kg-1, i.p.) immediately after training and one group remained uninjected serwing as control. Retention latencies were measured 48 h later. To asses a possible non-specific proactive effect of sildenafil, the response latencies in a group of rats not receiving foot shock were also tested. The results showed that the post-training i.p. administration of sildenafil did not facilitate retention performance of a passive avoidance response in both young and middle aged rats compared to control or vehicle groups. Also, sildenafil did not affect response latencies in rats not having received the footshock on the training trial, indicating that sildenafil does not show a non-specific proactive affect on retention performance. The comparison of retention time between young and middle aged rats showed that the memory of the latter had been significantly reduced. In conclusion, this study suggests that sildenafil has no effects on memory retention in Wistar rats.
Tumors such as prostate, small cell lung cancer, breast, gastric and colon cancer are known to overexpress receptors to bombesin
(BBN). In this study, a new bombesin analogue was labeled with 99mTc via HYNIC and tricine/EDDA as coligands and investigated further. HYNIC-GABA-Bombesin (7–14) NH2 was synthesized using a standard Fmoc strategy. Labeling with 99mTc was performed at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of radiopeptide
was checked in the presence of humane serum at 37 °C up to 24 h. The receptor bound internalization and externalization rates
were studied in GRP receptor expressing PC-3 cells. Biodistribution of radiopeptide was studied in nude mice bearing PC-3
tumor. Labeling yield of >98% was obtained corresponding to a specific activity of ~2.6 MBq/nmol. Peptide conjugate showed
good stability in the presence of human serum. The radioligand showed high and specific internalization into PC-3 cells (14.63 ± 0.41%
at 4 h). In biodistribution studies, a receptor-specific uptake was observed in GRP-receptor-positive organs so that after
4 h the uptakes in mouse tumor and pancreas were 1.31 ± 0.18 and 1.2 ± 0.13% ID/g, respectively.
Cefotaxime, a cephalosporin antibiotic, used to treat bacterial infections was investigated to label with 99mTc. Labeling was performed using sodium dithionite as a reducing agent at 100 °C for 10 min and radiochemical analysis involved
ITLC and HPLC methods. The stability of labeled antibiotic was checked in the presence of human serum at 37 °C up to 24 h.
The maximum radiolabeling yield was 92 ± 2%. Bacterial binding assay was performed with S. aureus and the in vivo distribution was studied in mice. Images showed minimal accumulation in non-target tissues, with an average
target/non-target ratio of 2.89 ± 0.58.
A variety of human tumors like prostate and breast cancer express bombesin receptors. Due to this a new bombesin analogue
was labeled with 99mTc via HYNIC and tricine as a coligand and investigated further. Peptide was synthesized on a solid phase using Fmoc strategy.
Labeling with 99mTc was performed at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of radiopeptide
was checked in the presence of human serum at 37 °C up to 24 h. Internalization was studied with the human GRP receptor cell
line PC-3. The biodistribution was studied in mice. Labeling yield of >98% was obtained corresponding to a specific activity
of ~80.9 GBq/μmol. Radiopeptide internalization into PC-3 cells was moderate and specific (10.7 ± 1.2% at 4 h). A high and
specific GRP receptor expressing mouse tumor and pancreas uptake (1.12 ± 0.08 and 1.04 ± 0.11% ID/g after 1 h respectively)
was also determined.