Adeno-associated virus-mediated ILK gene silencing in the rat NAc core

In this study we established conditional silencing of integrin-linked kinase (ILK) expression in Sprague-Dawley rat brain by microinjection of rAAV-2-carrying, Tet-On-regulated siRNA expression cassette into nucleus accumbens (NAc) core and induction with doxycycline. We demonstrated that inhibition of ILK expression was effectively induced by administration of doxycycline for 2 weeks while ILK expression was restored after withdrawing doxycycline for 8 days. Increases in GFAP and OX42 expression were observed 5 weeks post virus injection. Importantly, inhibition of ILK expression in the NAc core had no significant effect on cell apoptosis and animal basal locomotion and stereotypical behaviors, but decreased dendritic density of medium spiny neurons. Our studies suggest that: (1) rAAV-delivered Tet-On-regulated siRNA expression can conditionally regulate gene expression in rat brain; (2) inhibition of ILK expression has no significant effect on cell apoptosis and basal locomotor and stereotypical behaviors, but decreases dendritic density; and (3) microinjection of rAAV-2 causes inflammatory response around the injection track.

Effect of ischemic preconditioning and PKC activation on acidification during ischemia in rat heart

Ischemic preconditioning (PC) has been shown to attenuate intracellular acidification during a subsequent period of ischemia, to minimize stunning, and to decrease infarct size, PKC activation has been suggested to be involved in this phenomenon. The present study is designed to test whether PKC activation could mimic and PKC inhibition could block the PC effects on intracellular acidification during ischemia and on stunning during reflow in Langendorff perfused rat hearts. Prior to 20 min of sustained global normothermic ischemia, groups of hearts were treated with the PKC activators 4 beta-phorbol 12-myristate 13-acetate (PMA) or 1,2-dioctanoyl-srt-glycerol (DOG), a group of hearts was treated with the PKC inhibitor chelerythrine (CH), a group was treated with DOG plus CH, a group was preconditioned with four cycles of 5 min of ischemia and 5 min of reflow, and a group was treated with CH during PC. Recovery of left ventricular developed pressure (% of initial, pretreatment, preischemic LVDP), measured after 20 min of reflow, was improved in hearts treated with DOG, but not PMA (80 +/- 3% (DOG), 55 +/- 3% (PMA) v 51 +/- 3% (control), P < 0.05 between DOG and control), although both caused a similar degree of PKC translocation (measured by fractionation followed by an assay of PKC activity using incorporation of 32P into histone). The improved recovery of LVDP in the PC group and in the DOG group was blocked by chelerythrine. Measurement of pH (by 31P NMR) showed that DOG reduced acidification at 15-20 min of ischemia, although the effect was not as great as PC, while PMA did not reduce acidification. The effect of DOG on pHi was attenuated by CH; however, the PC-induced attenuation of the fall in pHi, was not affected by CH. High energy phosphates (measured by 31P NMR) were not significantly different between any of the groups during ischemia or reflow. This study confirms that the protective effect of ischemic preconditioning on stunning in rat heart can be eliminated by inhibition of PKC, but suggests that the effect of PC on the fall in pHi during sustained ischemia is not mediated by PKC.

Gonadotropin-releasing hormone neuronal cell lines

Gonadotropin-releasing hormone (GnRH) cell lines were developed by genetically targeted tumorigenesis in transgenic mice. The cell lines designated GT1 cells have a neuronal phenotype, express neuronal but not glial markers and express the GnRH gene at high levels. The GnRH prohormone is processed in the cells to multiple molecular forms including biologically active GnRH and GnRH-associated peptide. Basal secretion of GnRH from the cells is regulated in part by fast Na+ channels necessary for propagated action potentials. In many instances, basal GnRH release is pulsatile with an interpulse frequency similar to that seen in castrated rodents, suggesting that GnRH neurons are the pulse generator and are capable of synchronizing their secretion in vitro. The secretion of GnRH is stimulated by depolarization and by the neurotransmitter norepinephrine. In related studies we have demonstrated that expression of Simian virus 40 T antigen in GnRH neurons of transgenic mice leads to hypothalamic hypogonadism due to the inability of GnRH nerve terminals to organize in the median eminence. These findings support the use of genetically-directed tumorigenesis to establish highly differentiated GnRH neuronal cell lines that are a valuable model to study the cell biology and regulation of the neurons.

Role of angiotensin II and vasopressin in cisplatin-induced emesis

Cisplatin-containing chemotherapy regimens are known to produce intense nausea and vomiting. Angiotensin II (AII) and vasopressin (AVP) have been shown to have emetic properties. The role of these two peptides on cisplatin-induced vomiting was investigated in beagle dogs. Cisplatin (2 mg/kg, IV over 5 min) produced consistent emesis in all dogs after a mean latency time of 144 +/- 4 min. Serum Angiotensin Converting Enzyme (ACE) and plasma AII levels did not significantly change 3 hr after cisplatin administration (at the time of nausea and emesis) in control animals. AVP levels rose from 0.3 pg/ml to 7.5 pg/ml 3 hrs after cisplatin. Complete inhibition of ACE with enalapril (given at 3 mg/kg p.o., 3 hrs prior to cisplatin) reduced AII levels by 70%, but failed to significantly modify the increase in AVP levels (7.2 +/- 2.2 pg/ml), the latency time to emesis (149 +/- 2 min) and the number of emetic episodes induced by cisplatin. These results suggest that AII does not mediate cisplatin-induced emesis, nor does it mediate the increase in AVP observed at the time of emesis. We propose that AVP may be a good marker for nausea and emesis, and that increases in AVP may be neurally-mediated. The large increase in circulating AVP may represent a desirable water conservation response in anticipation of fluid losses induced by vomiting.