Functional inactivation of hypocretin 1 receptors in the medial prefrontal cortex affects the pyramidal neuron activity and gamma oscillations: An in vivo multiple-channel single-unit recording study

The hypocretin signaling is thought to play a critical role in maintaining wakefulness via stimulating the subcortical arousal pathways. Although the cortical areas, including the medial prefrontal cortex (mPFC), receive dense hypocretinergic fibers and express its receptors, it remains unclear whether the hypocretins can directly regulate the neural activity of the mPFC in vivo. In the present study, using multiple-channel single-unit recording study, we found that infusion of the SB-334867, a blocker for the Hcrtr1, beside the recording sites within the mPFC substantially exerted an inhibitory effect on the putative pyramidal neuron (PPN) activity in naturally behaving rats. In addition, functional blockade of the Hcrtr1 also selectively reduced the power of the gamma oscillations. The PPN activity and the power of the neural oscillations were not affected after microinjection of the TCS-OX2-29, a blocker for the Hcrtr2, within the mPFC. Together, these data indicate that endogenous hypocretins acting on the Hcrtr1 are required for the normal neural activity in the mPFC in vivo, and thus might directly contribute cortical arousal and mPFC-dependent cognitive processes.

Topical application of a new monoclonal antibody against fibroblast growth factor 10 (FGF 10) mitigates propranolol-induced psoriasis-like lesions in guinea pigs

OBJECTIVES

Psoriasis is a chronic inflammatory skin disease characterized by excessive proliferation of keratinocytes. Fibroblast growth factor 10 (FGF10) acts as a growth factor for keratinocyte proliferation. The aim of this study is to investigate whether FGF10 blockage, a new monoclonal antibody against FGF10 we generated, could mitigate topical propranolol-induced psoriasis-like lesions in guinea pigs.

MATERIALS AND METHODS

The monoclonal anti-FGF10 was generated by a routine method and purified by affinity chromatography. The effect of FGF10 and anti-FGF10 on human keratinocyte HaCaT cell proliferation was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The back of the ears of individual guinea pigs was topically exposed to 5% propranolol emulsion to induce psoriasis-like lesions and randomly treated topically with phosphate buffered saline (PBS), hydrocortisone butyrate, or different doses of anti-FGF10. The pathologic changes and the degrees of inflammation in the auricular areas of individual animals were examined histologically.

RESULTS

Characterization revealed that anti-FGF10 had a purity of 90% and a titer of 1:12800. We found that FGF10 stimulated HaCaT cell proliferation while treatment with different doses of anti-FGF10 inhibited FGF10-induced cell proliferation in a dose-dependent manner (100, 200 ng/ml, p < 0.05 vs. control; 400, 800, 1600 ng/ml, p < 0.01 vs. control). Compared to PBS-treated psoriatic animals, treatment with anti-FGF10, like hydrocortisone butyrate, greatly inhibited the severity of psoriasis-like lesions by reducing the Baker's scores, the thickness of epidermis, and the numbers of monocyte infiltrates in the dermis of animals.

CONCLUSIONS

The newly generated anti-FGF10 monoclonal antibody inhibited the proliferation of human keratinocytes in vitro and mitigated inflammation and pathogenic changes in propranolol-induced psoriasis-like lesions in animals. Therefore, these findings may provide a proof of principle that blockage of FGF-10 may inhibit psoriasis-related inflammation.

Presynaptic inhibition of GABAergic synaptic transmission by adenosine in mouse hypothalamic hypocretin neurons

Hypocretin neurons in the lateral hypothalamus, a new wakefulness-promoting center, have been recently regarded as an important target involved in endogenous adenosine-regulating sleep homeostasis. The GABAergic synaptic transmissions are the main inhibitory afferents to hypocretin neurons, which play an important role in the regulation of excitability of these neurons. The inhibitory effect of adenosine, a homeostatic sleep-promoting factor, on the excitatory glutamatergic synaptic transmissions in hypocretin neurons has been well documented, whether adenosine also modulates these inhibitory GABAergic synaptic transmissions in these neurons has not been investigated. In this study, the effect of adenosine on inhibitory postsynaptic currents (IPSCs) in hypocretin neurons was examined by using perforated patch-clamp recordings in the acute hypothalamic slices. The findings demonstrated that adenosine suppressed the amplitude of evoked IPSCs in a dose-dependent manner, which was completely abolished by 8-cyclopentyltheophylline (CPT), a selective antagonist of adenosine A1 receptor but not adenosine A2 receptor antagonist 3,7-dimethyl-1-(2-propynyl) xanthine. A presynaptic origin was suggested as following: adenosine increased paired-pulse ratio as well as reduced GABAergic miniature IPSC frequency without affecting the miniature IPSC amplitude. Further findings demonstrated that when the frequency of electrical stimulation was raised to 10 Hz, but not 1 Hz, a time-dependent depression of evoked IPSC amplitude was detected in hypocretin neurons, which could be partially blocked by CPT. However, under a higher frequency at 100 Hz stimulation, CPT had no action on the depressed GABAergic synaptic transmission induced by such tetanic stimulation in these hypocretin neurons. These results suggest that endogenous adenosine generated under certain stronger activities of synaptic transmissions exerts an inhibitory effect on GABAergic synaptic transmission in hypocretin neurons by activation of presynaptic adenosine A1 receptors, which may finely regulate the excitability of these neurons as well as eventually modulate the sleep-wakefulness.

Orexin A-induced extracellular calcium influx in prefrontal cortex neurons involves L-type calcium channels

Orexins, novel excitatory neuropeptides from the lateral hypothalamus, have been strongly implicated in the regulation of sleep and wakefulness. In this study, we explored the effects and mechanisms of orexin A on intracellular free Ca2+ concentration ([Ca2+]i) of freshly dissociated neurons from layers V and VI in prefrontal cortex (PFC). Changes in [Ca2+]i were measured with fluo-4/AM using confocal laser scanning microscopy. The results revealed that application of orexin A (0.1-1 microM) induced increase of [Ca2+]i in a dose-dependent manner. This elevation of [Ca2+]i was completely blocked by pretreatment with selective orexin receptor 1 antagonist SB 334867. While depletion of intracellular Ca2+ stores by the endoplasmic reticulum inhibitor thapsigargin (2 pM), [Ca2+]i in PFC neurons showed no increase in response to orexin A. Under extracellular Ca2+-free condition, orexin A failed to induce any changes of Ca2+ fluorescence intensity in these acutely dissociated cells. Our data further demonstrated that the orexin A-induced increase of [Ca2+]i was completely abolished by the inhibition of intracellular protein kinase C or phospholipase C activities using specific inhibitors, BIS II (1 microM) and D609 (10 microM), respectively. Selective blockade of L-type Ca2+ channels by nifedipine (5 microM) significantly suppressed the elevation of [Ca2+]i induced by orexin A. Therefore, these findings suggest that exposure to orexin A could induce increase of [Ca2+]i in neurons from deep layers of PFC, which depends on extracellular Ca2+ influx via L-type Ca2+ channels through activation of intracellular PLC-PKC signaling pathway by binding orexin receptor 1.