Controlled placement of multiple CNS cell populations to create complex neuronal cultures.

In vitro brain-on-a-chip platforms hold promise in many areas including: drug discovery, evaluating effects of toxicants and pathogens, and disease modelling. A more accurate recapitulation of the intricate organization of the brain in vivo may require a complex in vitro system including organization of multiple neuronal cell types in an anatomically-relevant manner. Most approaches for compartmentalizing or segregating multiple cell types on microfabricated substrates use either permanent physical surface features or chemical surface functionalization. This study describes a removable insert that successfully deposits neurons from different brain areas onto discrete regions of a microelectrode array (MEA) surface, achieving a separation distance of 100 µm. The regional seeding area on the substrate is significantly smaller than current platforms using comparable placement methods. The non-permanent barrier between cell populations allows the cells to remain localized and attach to the substrate while the insert is in place and interact with neighboring regions after removal. The insert was used to simultaneously seed primary rodent hippocampal and cortical neurons onto MEAs. These cells retained their morphology, viability, and function after seeding through the cell insert through 28 days in vitro (DIV). Co-cultures of the two neuron types developed processes and formed integrated networks between the different MEA regions. Electrophysiological data demonstrated characteristic bursting features and waveform shapes that were consistent for each neuron type in both mono- and co-culture. Additionally, hippocampal cells co-cultured with cortical neurons showed an increase in within-burst firing rate (p = 0.013) and percent spikes in bursts (p = 0.002), changes that imply communication exists between the two cell types in co-culture. The cell seeding insert described in this work is a simple but effective method of separating distinct neuronal populations on microfabricated devices, and offers a unique approach to developing the types of complex in vitro cellular environments required for anatomically-relevant brain-on-a-chip devices.

Paradoxical locomotor activating effects of kappa-opioid receptor stimulation in the preweanling rat: role of the ventromedial thalamus and superior colliculus.

Stimulating kappa-opioid receptors in the substantia nigra pars reticulata robustly increases the locomotor activity of preweanling rats. To determine whether nigrothalamic and nigrotectal connections are necessary for this kappa-opioid-mediated locomotor activity, preweanling rats were given a systemic injection of saline or 5 mg/kg U50,488 (a kappa-opioid receptor agonist) 2 days after receiving sham or bilateral electrolytic lesions of the ventromedial thalamus (VMT) or superior colliculus (SC). Results showed that lesions of the VMT and SC attenuated the U50,488-induced locomotor activity of preweanling rats, indicating that the locomotor activating effects of kappa-opioid receptor stimulation require that nigrothalamic and nigrotectal connections be intact.

Ultrasonic vocalizations of preweanling rats: involvement of both alpha(2)-adrenoceptor and kappa-opioid receptor systems.

Stimulation of alpha(2)-adrenoceptors and kappa-opioid receptors increases the ultrasonic vocalizations of preweanling rats. The purpose of the present study was to determine whether alpha(2)-adrenoceptors and kappa-opioid receptors modulate ultrasonic vocalization production via a common mechanism. To that end, 11-day-old rats were injected with the alpha(2)-adrenoceptor antagonist yohimbine (0, 0.5, or 1.0 mg/kg, i.p.) or the kappa-opioid receptor antagonist nor-binaltorphimine (0, 5, or 10 mg/kg, i.p.). After 15 min, the same rats were injected with saline, the alpha(2)-adrenoceptor agonist clonidine (0.25 mg/kg, i.p.), or the kappa-opioid receptor agonist trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate (U-50,488; 2.5 mg/kg, i.p.). Results showed that both clonidine and U-50,488 increased the ultrasonic vocalizations of preweanling rats. Not surprisingly, clonidine-induced ultrasonic vocalizations were blocked by yohimbine, while U-50,488-induced vocalizations were blocked by nor-binaltorphimine. Importantly, yohimbine also attenuated the vocalizations produced by U-50,488, whereas nor-binaltorphimine did not alter clonidine-induced ultrasonic vocalizations. Thus, it appears that alpha(2)-adrenoceptor and kappa-opioid receptor stimulation increases ultrasonic vocalization production via a common mechanism. It is likely that the kappa-opioid receptors responsible for modulating ultrasonic vocalizations are located "upstream" from the alpha(2)-adrenoceptors.

Epidermal growth factor inhibits carbachol-stimulated canine parietal cell function via protein kinase C.

BACKGROUND & AIMS: Epidermal growth factor (EGF) inhibits secretagogue-stimulated gastric acid secretion via an EGF receptor located on parietal cells. The aim of this study was to examine whether this growth factor inhibited carbachol-stimulated acid secretion through a protein kinase C-dependent mechanism. METHODS: The effect of EGF on carbachol-stimulated aminopyrine uptake, inositol trisphosphate formation, and intracellular Ca2+ ([Ca2+]i) in purified cultured parietal cells was studied. The ability of protein kinase A and C inhibitors to alter the inhibitory action of EGF was assessed. EGF-mediated translocation and activation of protein kinase C in parietal cells were determined. RESULTS: EGF dose dependently inhibited carbachol-stimulated aminopyrine uptake in a pertussis toxin-insensitive, genistein (tyrosine kinase inhibitor)--sensitive manner, with a maximal inhibitory effect (37.5% +/- 6.8%) achieved at 10(-7) mol/L. EGF did not significantly inhibit carbachol-stimulated inositol trisphosphate formation and did not alter the initial transient increase or sustained plateau in [Ca2+]i stimulated by this secretagogue. The protein kinase C inhibitors H-7 and staurosporine dose dependently reversed the inhibitory action of EGF, whereas H-89 (protein kinase A inhibitor) failed to alter the effect of EGF. EGF pretreatment increased the translocation of alpha and beta 1 isoforms of protein kinase C and stimulated kinase activity in parietal cells. EGF did not down-regulate the parietal cell muscarinic receptor. CONCLUSIONS: The inhibitory action of EGF on carbachol-stimulated parietal cell activity seems to involve protein kinase C.

An interpretive analysis of precepting an unsafe student.

Precepting students during their senior practicum is often viewed as an opportunity to nurture the next generation of nurses. However, when the student has only marginally passed courses or clinical experiences, precepting may become a difficult and challenging process. Little is known about how preceptors teach students and even less is known about precepting unsafe students. The purpose of this article is to describe a preceptor's journey through a difficult senior practicum experience. A hermeneutic analysis of the preceptor's journal revealed two themes important in precepting the unsafe student: knowing the student and creating possibilities for success. Two aspects of knowing the student included watchful listening and assessing dangerousness. These themes are described and the dilemma of bringing an unsafe nurse into the profession is discussed.