Alpha 1-adrenoceptors in the adult rat barrel field: effects of deafferentation and norepinephrine removal.
Norepinephrine (NE), acting on brain adrenoceptors, plays an important role in barrel field neuronal activity and plasticity. For this reason, the distribution of alpha 1- and alpha 2-adrenoceptors in the somatosensory cortex barrel field was studied by autoradiographic techniques in rats undergoing plastic change or NE depletion. In layers IV and V of the cortex, the pattern of alpha 1-adrenoceptors (assessed by [3H]prazosin binding) varied across the barrel field. There was relatively low binding within the barrels themselves, with 21% higher binding in the surrounding septa. alpha 2-Adrenoceptor binding (assessed with [3H]paraminoclonidine) was almost homogeneous across the entire barrel field. Two weeks after noradrenergic deafferentation by unilateral lesioning of the locus coeruleus, there was a 16% upregulation of [3H]prazosin binding. This then returned to control levels of by 8 weeks. Peripheral deafferentation of sensory input to the barrel field produced the opposite effect on alpha 1-adrenoceptors. Unilateral removal of all but the central (C3) vibrissa (which induces plastic changes in the cortical representation of the spared virbrissa) caused a 12% decrease in [3H]prazosin binding in the whole barrel field at 2 weeks after surgery which returned to normal by 8 weeks. Therefore, alpha 1-adrenoceptors in the barrel field of the rat are affected in opposite ways by changes in NE content and afferent sensory input. We hypothesize that alpha 1-adrenoceptor levels are modulated after vibrissectomy through either an indirect reaction to reduced cortical gamma-aminobutyric acid levels, or by a reordering of metabolic priorities during plastic change of the cortical neuronal network.
Dunn-Meynell
A A
AA
Department of Veterans Affairs Medical Center, East Orange, NJ 07018.
Levin
B E
BE
D000344:Afferent Pathways / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D001345:Autoradiography; D007839:Functional Laterality; D008125:Locus Coeruleus / Q000502:physiology; D008297:Male; D009474:Neurons / Q000378:metabolism*; D009638:Norepinephrine / Q000502:physiology*; D011224:Prazosin / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D018341:Receptors, Adrenergic, alpha-2 / Q000378:metabolism; D013003:Somatosensory Cortex / Q000378:metabolism*; D013997:Time Factors; D014316:Tritium; D014738:Vibrissae / Q000294:innervation*
D018340:Receptors, Adrenergic, alpha-1; D018341:Receptors, Adrenergic, alpha-2; D014316:Tritium; D009638:Norepinephrine; D011224:Prazosin