Effect of vertical stopcock position on start-up fluid delivery in syringe pumps used for microinfusions

The purpose of this in vitro study was to evaluate the impact of the vertical level of the stopcock connecting the infusion line to the central venous catheter on start-up fluid delivery in microinfusions. Start-up fluid delivery was measured under standardized conditions with the syringe outlet and liquid flow sensors positioned at heart level (0 cm) and exposed to a simulated CVP of 10 mmHg at a set flow rate of 1 ml/h. Flow and intraluminal pressures were measured with the infusion line connected to the stopcock primarily placed at vertical levels of 0 cm, + 30 cm and - 30 cm or primarily placed at 0 cm and secondarily, after connecting the infusion line, displaced to + 30 cm and - 30 cm. Start-up fluid delivery 10 s after opening the stopcock placed at zero level and after opening the stopcock primarily connected at zero level and secondary displaced to vertical levels of + 30 cm and - 30 cm were similar (- 10.52 [- 13.85 to - 7.19] µL; - 8.84 [- 12.34 to - 5.33] µL and - 11.19 [- 13.71 to - 8.67] µL (p = 0.469)). Fluid delivered at 360 s related to 65% (zero level), 71% (+ 30 cm) and 67% (- 30 cm) of calculated infusion volume (p = 0.395). Start-up fluid delivery with the stopcock primarily placed at + 30 cm and - 30 cm resulted in large anterograde and retrograde fluid volumes of 34.39 [33.43 to 35.34] µL and - 24.90 [- 27.79 to - 22.01] µL at 10 s, respectively (p < 0.0001). Fluid delivered with the stopcock primarily placed at + 30 cm and - 30 cm resulted in 140% and 35% of calculated volume at 360 s, respectively (p < 0.0001). Syringe infusion pumps should ideally be connected to the stopcock positioned at heart level in order to minimize the amounts of anterograde and retrograde fluid volumes after opening of the stopcock.

Pressure-adjusted venting eliminates start-up delays and compensates for vertical position of syringe infusion pumps used for microinfusion

Microinfusions are commonly used for the administration of catecholamines, but start-up delays pose a problem for reliable and timely drug delivery. Recent findings show that venting of the syringe infusion pump with draining of fluid to ambient pressure before directing the flow towards the central venous catheter does not counteract start-up delays. With the aim to reduce start-up delays, this study compared fluid delivery during start-up of syringe infusion pumps without venting, with ambient pressure venting, and with central venous pressure (CVP)-adjusted venting. Start-up fluid delivery from syringe pumps using a microinfusion of 1 mL/h was assessed by means of liquid flow measurement at 10, 60, 180 and 360 s after opening the stopcock and starting the pump. Assessments were performed using no venting, ambient pressure venting or CVP-adjusted venting, with the pump placed either at zero, - 43 cm or + 43 cm level and exposed to a simulated CVP of 10 mmHg. Measured fluid delivery was closest to the calculated fluid delivery for CVP-adjusted venting (87% to 100% at the different timepoints). The largest deviations were found for ambient pressure venting (- 1151% to + 82%). At 360 s after start-up 72% to 92% of expected fluid volumes were delivered without venting, 46% to 82% with ambient pressure venting and 96% to 99% with CVP-adjusted venting. CVP-adjusted venting demonstrated consistent results across vertical pump placements (p = 0.485), whereas the other methods had significant variances (p < 0.001 for both). In conclusion, CVP-adjusted venting effectively eliminates imprecise drug delivery and start-up delays when using microinfusions.

Selective sub-nucleus effects of intra-amygdala oxytocin on fear extinction

There is growing evidence that the neuropeptide oxytocin (OT) modulates fear and extinction in humans and rodents through actions in corticolimbic circuits including the central amygdala (CeA). Prior studies have, however, been limited to subjects that exhibit intact basal extinction, rather than extinction-impaired populations that could potentially therapeutically benefit from viable OT-targeting treatments. Here, we assessed the effects of pre-extinction training infusion of OT into the CeA, or basolateral amygdala (BLA), on extinction in an inbred mouse strain (S1) model of impaired extinction. We found that intra-CeA OT, at a dose of 0.01 μg, enabled extinction memory formation, as evidenced by lesser freezing as compared to vehicle-infused controls on a drug-free retrieval test. Conversely, infusion of a higher, 1.0 μg OT dose, markedly reduced freezing and increased grooming during extinction training and produced elevated freezing on drug-free retrieval. Infusion of the 0.01 μg dose into the BLA was without behavioral effects. Together, our data show that OT acts in a dose-dependent manner within the CeA to promote extinction in otherwise extinction-deficient mice. These findings provide further support for the potential utility of OT as an adjunctive treatment to extinction-based therapies for trauma and anxiety disorders.

Physiological approaches to understanding molecular actions on dorsolateral prefrontal cortical neurons underlying higher cognitive processing

Revealing how molecular mechanisms influence higher brain circuits in primates will be essential for understanding how genetic insults lead to increased risk of cognitive disorders. Traditionally, modulatory influences on higher cortical circuits have been examined using lesion techniques, where a brain region is depleted of a particular transmitter to determine how its loss impacts cognitive function. For example, depletion of catecholamines or acetylcholine from the dorsolateral prefrontal cortex produces striking deficits in working memory abilities. More directed techniques have utilized direct infusions of drug into a specific cortical site to try to circumvent compensatory changes that are common following transmitter depletion. The effects of drug on neuronal firing patterns are often studied using iontophoresis, where a minute amount of drug is moved into the brain using a tiny electrical current, thus minimizing the fluid flow that generally disrupts neuronal recordings. All of these approaches can be compared to systemic drug administration, which remains a key arena for the development of effective therapeutics for human cognitive disorders. Most recently, viral techniques are being developed to be able to manipulate proteins for which there is no developed pharmacology, and to allow optogenetic manipulations in primate cortex. As the association cortices greatly expand in brain evolution, research in nonhuman primates is particularly important for understanding the modulatory regulation of our highest order cognitive operations.

Effects of stimulation of muscarinic acetylcholine receptors in medial septum on some immune responses in rats

OBJECTIVES

Though the immunomodulatory role of medial septum (MS) has been indicated, but the contribution of the muscarinic acetylcholine (mAch) receptors presented in the internal network of the neurons of MS in this regard is not known. The aim of the present study is to assess the contribution of mAch receptors of MS on some immunological parameters.

METHODS

Different immunological parameters i.e. phagocytic activity of peripheral leukocytes, adhesibility and cytotoxicity of splenic mononuclear cells (MNC), delayed type of hypersensitivity (DTH) responses, Total Count (TC) and Differential Count (DC) of WBC with serum corticosterone (CORT) concentration have been measured after stimulation and blocking of mAch receptors of MS in rats. Ach or atropine has been micro infused into MS of separate groups of rats for stimulating or blocking of the mAch receptors respectively.

RESULTS

In Ach or atropine microinfused rats, the TC of WBC remained unaltered in the present study. The percentage of neutrophil has increased and the percentage of lymphocyte has decreased in Ach microinfused rats, but these parameters remain unaltered in atropine microinfused rats. The observed immunological parameters have increased after microinfusion of 0.60μM and 0.12μM of Ach and serum CORT concentration has decreased in those animals. These immunological parameters have decreased and serum CORT has increased after microinfusion of atropine (2 and 4mM) in MS of rats.

CONCLUSION

It appears that the Ach receptors in MS can modulate the observed immunological parameters, and serum CORT plays an important role for these immune changes.

The bed nucleus of the stria terminalis regulates ethanol-seeking behavior in mice

Drug-associated stimuli are considered important factors in relapse to drug use. In the absence of drug, these cues can trigger drug craving and drive subsequent drug seeking. One structure that has been implicated in this process is the bed nucleus of the stria terminalis (BNST), a chief component of the extended amygdala. Previous studies have established a role for the BNST in cue-induced cocaine seeking. However, it is unclear if the BNST underlies cue-induced seeking of other abused drugs such as ethanol. In the present set of experiments, BNST involvement in ethanol-seeking behavior was assessed in male DBA/2J mice using the conditioned place preference procedure (CPP). The BNST was inhibited during CPP expression using electrolytic lesions (Experiment 1), co-infusion of GABAA and GABAB receptor agonists muscimol and baclofen (M+B; Experiment 2), and activation of inhibitory designer receptors exclusively activated by designer drugs (hM4Di-DREADD) with clozapine-N-oxide (CNO; Experiment 3). The magnitude of ethanol CPP was reduced significantly by each of these techniques. Notably, infusion of M+B (Exp. 2) abolished CPP altogether. Follow-up studies to Exp. 3 showed that ethanol cue-induced c-Fos immunoreactivity in the BNST was reduced by hM4Di activation (Experiment 4) and in the absence of hM4Di, CNO did not affect ethanol CPP (Experiment 5). Combined, these findings demonstrate that the BNST is involved in the modulation of cue-induced ethanol-seeking behavior.

Functional role for mouse cerebellar NO/cGMP/KATP pathway in ethanol-induced ataxia

BACKGROUND

We have previously shown that brain adenosine A1 receptors and nitric oxide (NO) play an important role in ethanol (EtOH)-induced cerebellar ataxia (EICA) through glutamate/NO/cGMP pathway. I now report possible modulation of EICA by the cerebellar NO/cGMP/K(ATP) pathway.

METHODS

EICA was evaluated by Rotorod in CD-1 male mice. All drugs (K(ATP) activators pinacidil, 0.05, 0.1, 0.5 nmol; minoxidil, 0.01, 0.1, 1.0 pmol; antagonists glipizide/glibenclamide, 0.01, 0.05, 0.1 nmol; NO donor l-arginine, 20 nmol; NOS inhibitors [iNOS] inhibitor L-NAME, 50 nmol; glutamate, 1.5 nmol; adenosine A1 receptor agonist N(6) -cyclohexyladenosine [CHA], 6, 12 pmol; antagonist DPCPX, 0.1 or 0.4 nmol) were given by direct intracerebellar microinfusion via stereotaxically implanted guide cannulas, except EtOH (2 g/kg, i.p.).

RESULTS

Pinacidil and minoxidil dose-dependently accentuated, whereas glipizide and glibenclamide markedly attenuated EICA, indicating tonic participation of K(ATP) channels. Glipizide abolished the pinacidil potentiation of EICA, which confirmed both drugs acted via K(ATP) channels. A possible link between K(ATP) channels and glutamate/NO pathway was suggested when (i) CHA (12 pmol) totally abolished l-arginine-induced attenuation of EICA; (ii) L-NAME abolished l-arginine-induced attenuation of EICA associated with further increase in EICA; and (iii) the combined l-arginine and glutamate infusion virtually abolished EICA. Also, whereas CHA abolished glibenclamide-induced attenuation and potentiated pinacidil/minoxidil-induced accentuation of EICA, the effects of DPCPX were just the opposite to those of CHA.

CONCLUSIONS

The results with CHA therefore suggest a functional link between K(ATP) and A1 receptors and between K(ATP) and glutamate/NO and as an extension may involve participation of NO/cGMP/K(ATP) pathway in EICA.