The subventricular zone (SVZ) produces neuroblasts that migrate to the olfactory bulb and differentiate into periglomerular (PG) and granule cells throughout postnatal life. While such postnatally generated intemeurons have been characterized morphologically, their physiological differentiation has not been thoroughly described. Combining retroviral- mediated labelling of newly generated neurons with patch-clamp electrophysiology, we demonstrate that soon after new cells enter the olfactory bulb they display voltage-dependent currents typical of more mature neurons. We further show that these "newcomers" establish synaptic contacts with the existing neuronal network, and are responsive to GABA and glutamate. A significant fraction of PG cells is known to be dopaminergic (DA), but the functional properties of these cells have never been investigated. Using transgenic mice expressing a reporter protein (eGFP) under the tyrosine hydroxylase promoter we show that among the cells added in adulthood in the glomerular layer there are also DA neurones, of two different types. We have studied their properties, and we show that most of them (about 60%) fire spontaneously in the absence of synaptic inputs. Both in slices and after enzymatic dissociation DA neurones generated action potentials in a highly rhythmic fashion at about 4- 8 Hz. We found that interspike depolarisation was driven by substantial components of TTX- sensitive, non inactivating Na+ current and a voltage-dependent, L-type Ca2+ current, whereas no contribution of hyperpolarisation-activated cation current (Ih) could be evidenced. Finally, the pace-making currents have been kinetically and pharmacologically characterised, and their interplay in the generation of rhythmic pattern has been reconstructed in numerical simulations.
FUNCTIONAL PROPERTIES OF ADULT-BORN JUXTAGLOMERULAR CELLS IN THE MAMMALIAN OLFACTORY BULB
BELLUZZI, Ottorino;PIGNATELLI, Angela;
2004
Abstract
The subventricular zone (SVZ) produces neuroblasts that migrate to the olfactory bulb and differentiate into periglomerular (PG) and granule cells throughout postnatal life. While such postnatally generated intemeurons have been characterized morphologically, their physiological differentiation has not been thoroughly described. Combining retroviral- mediated labelling of newly generated neurons with patch-clamp electrophysiology, we demonstrate that soon after new cells enter the olfactory bulb they display voltage-dependent currents typical of more mature neurons. We further show that these "newcomers" establish synaptic contacts with the existing neuronal network, and are responsive to GABA and glutamate. A significant fraction of PG cells is known to be dopaminergic (DA), but the functional properties of these cells have never been investigated. Using transgenic mice expressing a reporter protein (eGFP) under the tyrosine hydroxylase promoter we show that among the cells added in adulthood in the glomerular layer there are also DA neurones, of two different types. We have studied their properties, and we show that most of them (about 60%) fire spontaneously in the absence of synaptic inputs. Both in slices and after enzymatic dissociation DA neurones generated action potentials in a highly rhythmic fashion at about 4- 8 Hz. We found that interspike depolarisation was driven by substantial components of TTX- sensitive, non inactivating Na+ current and a voltage-dependent, L-type Ca2+ current, whereas no contribution of hyperpolarisation-activated cation current (Ih) could be evidenced. Finally, the pace-making currents have been kinetically and pharmacologically characterised, and their interplay in the generation of rhythmic pattern has been reconstructed in numerical simulations.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
