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The influence of orexins on the firing rate and pattern of rat intergeniculate leaflet neurons – electrophysiological and immunohistological studies
Author(s) -
Pekala Dobromila,
Blasiak Tomasz,
Raastad Morten,
Lewandowski Marian H.
Publication year - 2011
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2011.07868.x
Subject(s) - electrophysiology , leaflet (botany) , neuroscience , biology , botany
Orexins influence various physiological processes associated with feeding behaviour, endocrine functions and wakefulness. One component of mammalian circadian timing systems, intergeniculate leaflet (IGL) of the lateral geniculate nucleus, is thought to contribute to circadian entrainment by processing photic and non‐photic/arousal‐related signals. Because the IGL is possibly innervated by the orexinergic system, using in vitro extracellular recording techniques we evaluated the influence of orexin A (OXA) and orexin B (OXB) on the rate and pattern of neuronal firing in this structure. Significant increases in the activity of 33 and 28% of IGL cells were observed after locally applied OXA (1 μ m ) and OXB (1 μ m ), respectively. In the great majority of neurons responses to OXA were maintained in the presence of orexin‐1 receptor OX1R antagonist, SB 334867 (10 μ m ). Additionally, 75% of the OXB‐responsive neurons were also sensitive to an orexin‐2 receptor (OX2R)‐selective agonist, [Ala11, D‐Leu15]‐OXB (1 μ m ). Immunohistochemical stainings showed putative synaptic contacts between OXA‐ and OXB‐immunoreactive fibres and neuropeptide Y, and enkephalin‐positive neurons in the investigated area. The outcome of our experiments reinforces previous reports indicating the possible linkage between the orexinergic and circadian systems. To our knowledge the presented findings are the first showing the direct influence of orexins on the IGL activity, mostly through activation of OX2R.