Effects of <Emphasis Type="SmallCaps">d</Emphasis>-kyotorphin on nociception and NADPH-d neurons in rat’s periaqueductal gray after immobilization stress

d-kyotorphin (d-Kyo) is a synthetic analogue of the neuropeptide kyotorphin and produces naloxone reversible analgesia. Stress-induced analgesia (SIA) is an in-built mammalian pain-suppression response that occurs during or following exposure to a stressful stimulus. The periaqueductal gray (PAG) is implicated as a critical site for processing strategies for coping with different types of stress and pain and NO affects its activity. The objectives of the present study were twofold: (1) to examine the effects of d-Kyo (5 mg/kg) on acute immobilization SIA; (2) to investigate the effect of peptide on NO activity in rat PAG after the stress procedure mentioned above. All drugs were injected intraperitoneally in male Wistar rats. The nociception was measured by the paw pressure and hot plate tests. A histochemical procedure for nicotinamide adenine dinucleotide phosphate–diaphorase (NADPH-d)-reactive neurons was used as indirect marker of NO activity. Our results revealed that d-Kyo has modulating effects on acute immobilization stress-induced analgesia in rats may be by opioid and non-opioid systems. Although d-Kyo is incapable of crossing the blood–brain barrier it showed an increased number of NADPH-d reactive neurons in dorsolateral periaqueductal gray (dlPAG) in control but not in stressed groups. We may speculate that the effect of d-Kyo in the brain is due to structural and functional interaction between opioidergic and NO-ergic systems or d-Kyo appears itself as a stressor. Further studies are needed to clarify the exact mechanisms of its action.     

Does hypothyroidism augment sun-induced skin damage?

Objectives: We investigated the mutual effects of overt hypothyroidism and prolonged sunlight exposure on free radical accumulation and oxidative skin damage.

Methods: Free radical accumulation was evaluated by monitoring the transformation of 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) into MTT-formazan. The pro-oxidant enzymes xanthine oxidase (XO) and NADPH-diaphorase were measured in the skin. XO activity was estimated based on the yield of uric acid, while NADPH-diaphorase reactivity was monitored histochemically as an indirect marker of nitric oxide synthase and nitric oxide activity. Cellular damage was determined by malondialdehyde formation, a marker for lipid peroxidation.

Results: In the skin of both euthyroid and hypothyroid animals, solar simulated ultraviolet irradiance increased the activity of XO and the NADPHdiaphorase reactivity as a protective response to formation of free radicals, such as reactive oxygen or nitrogen species. These pro-oxidant enzymes diminished in hypothyroid rats. Accumulation of the same amount of free radicals led to similar peroxidation in both hypothyroid and irradiated euthyroid rats. Hypothyroid skin after UV-exposure showed even greater lipid peroxidation.

Discussion: The hypothyroid state could be a risk factor for enhanced oxidative skin damage in chronic photo-exposed skin due to oxidative stress. The lipid peroxidation is one of the major pathways by which photo-oxidative stress promotes photocarcinogenesis and photo-aging.     

Light and electron-microscopic study of leucine enkephalin immunoreactivity in the cat claustrum

The claustrum is a complex telencephalic structure owing to its reciprocal connectivity with most—if not all—cortical areas. However, there is a paucity of data in the literature concerning its histochemical components, including opioid peptide neurotransmitters. The aim of the present study was to examine the morphology, distribution and ultrastructure of leucine-enkephalin-immunoreactive (Leu-enk-ir) neurons and fibers in the dorsal claustrum (DC) of the cat. Seven healthy, adult male and female cats were used in our study. All animals received humane care. They were irreversibly anesthetized and transcardially perfused with fixative. Brains were removed, postfixed, blocked and sectioned. Sections were incubated with polyclonal anti-Leu-enk antibodies using the Avidin–Biotin–Peroxidase Complex method. Leu-enk-ir neurons and fibers were distributed throughout the DC. Some of the neurons were lightly-stained, while others were darkly-stained. Light-microscopically, they varied in shape: oval, fusiform, multipolar and irregular. With regard to size, they were categorized as small (15?μm or less in diameter), medium (16–20?μm in diameter) and large (21?μm or more in diameter). No specific pattern of regional distribution was found. On the electron microscope level, immunoproduct was observed in neurons, dendrites and terminal boutons. Different types of Leu-enk-ir neurons differ in their ultrastructural features, including two types of synaptic boutons. No gender-specific features were observed. In conclusion, it is our hope that our study will serve to contribute to a better understanding of the functional neuroanatomy of the DC in the cat, and that it can be extrapolated and applied to other mammals, including humans.     

Central,but not systemic,thermoregulatory effects of leptin are impaired in rats with obesity: interactions with GABAB agonist and antagonist

Amino Acids - Leptin is an adipokine that regulates body weight by decreasing appetite and increasing energy expenditure. Besides the effects on food intake, leptin can regulate energy expenditure...