Discovery of E/Z or trans-cis photoisomerization in the azobenzenes and their derivatives had the tremendous impact on the whole domain of photochromic materials including photochromic polymers and liquid crystals. Here we show similar configurational photoinduced transformation in a simple derivative of pyrazoline. The X-ray crystallographic investigations of (E)-3-(4-nitrostyryl)-1-phenyl-4,5-dihydro-1H-pyrazole (abbreviated as PYpNO 2 ) in grown crystals show two different structures comprising of either cis or trans molecules. The performed quantum chemical calculations confirm the existence of both configurations of PY-pNO 2 at the room temperature. Photophysical properties of this compound derived from quantum chemical calculations predict possibility of trans to cis switching of PY-pNO 2 by light. Indeed, molecules of PY-pNO 2 embedded in PMMA polymeric matrix when illuminated with 532 nm linearly polarized laser light show the induced optical anisotropy, i.e. birefringence characteristic for photoisomerizable molecules similar like in the group of the azobenzene derivatives.

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The participation of peripheral peptides in the processes regulating the food intake (energy homeostasis) at the central nervous system level remains unclear. This study focuses on the role of obestatin in neuronal activity within the hypothalamic appetite-regulating network in ruminants. The animals (n = 28) were randomly divided into two groups. The sheep in the control group received intracerebroventricular infusions of the Ringer-Locke solution, and the sheep in obestatin group were infused with obestatin (diluted in the Ringer-Locke solution) at 25 μg per 120 μl/hr. The series of four 1-hr infusions on 3 consecutive days were performed, and immediately after the experiment, the sheep were decapitated. Selected brain regions were fixed in situ for further immunohistochemical analysis, while the remaining ones were frozen for real-time RT-qPCR analysis. Obestatin infusion elicited changes in the neuropeptide Y (NPY) neuronal network in the hypothalamus. The results obtained show that exogenous obestatin evoked an increase in npy and agrpmRNA expression in the mediobasal hypothalamus (MBH), while the immunoreactivity for NPY was decreased in the arcuate and periventricular nuclei. The increase in cart and pomcmRNA expression in the MBH was also observed. Moreover, increased levels of gpr39 receptor and npy receptor 1 mRNA expression were evident in obestatin-infused sheep. Based on these results, it can be concluded that obestatin plays a role in the modulation of appetite-regulating network at the central level in sheep. The results obtained suggest that the underlying mechanism may involve the modification of the activity of NPY/AgRP and CART/α-MSH neurons in the arcuate nucleus.