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N Rawlings

Publications and source records attributed to N Rawlings.

4 recordsLinked to original sources
PubMed2001

Effects of neurotensin on discharge rates of rat suprachiasmatic nucleus neurons in vitro.

The neuropeptide neurotensin and two classes of its receptors, the neurotensin receptor-1 and 2, are present in the suprachiasmatic nucleus of the mammalian hypothalamus. The suprachiasmatic nucleus houses the mammalian central circadian pacemaker, but the effects of neurotensin on cellular activity in this circadian pacemaker are unknown. In this study, we examined the effects of neurotensin on the spontaneous discharge rate of rat SCN cells in an in vitro slice preparation. Neurotensin (1-10 microM) increased cell firing rate in approximately 50% of cells tested, while approximately 10% of suprachiasmatic cells tested showed a decrease in firing rate in response to neurotensin. These effects of neurotensin were not altered by the GABA receptor antagonist bicuculline (20 microM) or the glutamate receptor antagonists, D-aminophosphopentanoic acid (50 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (20 microM). The neurotensin receptor selective antagonists SR48692 and SR142948a (10 microM) failed to antagonise neurotensin responses in the majority of cells examined. Compounds that function as agonists selective for the neurotensin-receptor subtypes 1 and 2, JMV-510 and JMV-431 respectively, elicited neurotensin-like responses in approximately 90% of cells tested. Six out of seven cells tested responded to both JMV-510 and JMV-431. Neuropeptide Y (100nM) treatment of suprachiasmatic nucleus slices was found to elicit profound suppression of neuronal firing rate. Co-application of neurotensin with neuropeptide Y significantly (P<0.05) reduced the duration of the response, as compared to that elicited with neuropeptide Y alone. Together, these results demonstrate for the first time the actions of neurotensin in the suprachiasmatic nucleus and raise the possibility that this neuropeptide may play a role in modulating circadian pacemaker function.

Animals↗
PubMed2001

Expression of integrin alphavbeta3 in pig, dog and cattle.

The alphavbeta3 integrin, also known as vitronectin receptor, is an adhesive glycoprotein that promotes angiogenesis in the embryo and tumors such as melanoma. Integrin alphavbeta3 is one of the receptors for adenovirus and hantavirus. There is little information on the constitutive expression of this integrin especially in animal species that are used for biomedical research. We used light and electron microscope immunocytochemistry and western blots to determine integrin alphavbeta3 expression in seven organs in the pig, dog and cattle. Immunohistology showed the integrin expression on the epithelium of small intestine, bile duct and renal proximal convoluted tubules in three species. The airway epithelium revealed a weak reaction for integrin alphavbeta3. Skin showed the integrin in occasional extravascular cells while skeletal muscles were negative. The integrin was expressed only in bronchial vasculature in the lung and occasional dermal microvessels. Many mononuclear cells in the lung and spleen stained for integrin alphavbeta3. Immunogold electron microscopy revealed the expression on the epithelium but not on the vasculature of the small intestine. Western blots detected integrin alphavbeta3 in small intestine and lung but not in skeletal muscles. We conclude the integrin is expressed on the epithelium but not in the vasculature. The expression differs strikingly among organs in the same species although the inter-species differences are minor. Restriction of the integrin to absorptive epithelia of small intestine and kidney may suggest its putative role in endocytosis. Because the integrin is a receptor for adenovirus, these data may be relevant to gene therapy studies.

Animals↗