Electrophysiological and morphological characteristics of three subtypes of rat globus pallidus neurone in vitro

Abstract

1. Neurones of the globus pallidus (GP) have been classified into three subgroups based on the visual inspection of current clamp electrophysiological properties and morphology of biocytin-filled neurones. 2. Type A neurones (132Ï208; 63%) were identified by the presence of the time-and voltagedependent inward rectifier (Ih) and the low-threshold calcium current (It) giving rise to anodal break depolarisations. These cells were quiescent or fired regular spontaneous action potentials followed by biphasic AHPs. Current injection evoked regular activity up to maximum firing frequency of 350 Hz followed by moderate spike frequency adaptation. The somata of type A cells were variable in shape (20 ² 12 ìm) while their dendrites were highly varicose. 3. Type B neurones (66Ï208; 32%) exhibited neither Ih nor rebound depolarisations and only a fast monophasic AHP. These cells were spontaneously active while current injection induced irregular patterns of action potential firing up to a frequency of 440 Hz with weak spike frequency adaptation. Morphologically, these cells were the smallest encountered (15 ² 10 ìm), oval in shape with restricted varicose dendritic arborisations. 4. Type C neurones were much rarer (10Ï208; 5%). They were identified by the absence of Ih and rebound depolarisations, but did possess a prolonged biphasic AHP. They displayed large A-like potassium currents and ramp-like depolarisations in response to step current injections, which induced firing up to a maximum firing frequency of 310 Hz. These cells were the largest observed (27 ² 15 ìm) with extensive dendritic branching. 5. These results confirm neuronal heterogeneity in the adult rodent GP. The driven activity and population percentage of the three subtypes correlates well with the in vivo studies (Kita & Kitai, 1991). Type A cells appear to correspond to type II neurones of Nambu & Llinas (1994, 1997 while the small diameter type B cells display morphological similarities with those described by Millhouse (1986). The rarely encountered type C cells may well be large cholinergic neurones. These findings provide a cellular basis for the study of intercellular communication and network interactions in the adult rat in vitro. Keywords:

Distinct Functional Roles of the Metabotropic Glutamate Receptors 1 and 5 in the Rat Globus Pallidus

“…A consensus from many studies is that type A, also referred to as type II neurons (Nambu and Llinas, 1994;Stanford and Cooper, 1999;Shindou et al, 2001), are the predominant electrophysiological phenotype in the rodent GP (Cooper and Stanford, 2000). Here, we report that activation of mGluR1, but not mGluR5, depolarizes type II GP neurons.…”

“…1 B). This cellular phenotype closely corresponds to type II or type A GP neurons described previously by Nambu and Llinas (1994), Cooper and Stanford (2000), and Shindou et al (2001). Type II neurons are also thought to be the predominant cellular subtype encountered in the rat GP during in vivo recordings (Hassani et al, 1996).…”

“…The first property was a sag in membrane potential during a hyperpolarizing current injection in current clamp that corresponds to a time-and voltage-dependent inward current I h . The second property was the presence of anodal breaks after a hyperpolarizing step, suggesting the presence of a low-threshold-activated Ca 2ϩ current I t (Nambu and Llinas, 1994;Stanford and Cooper, 1999;Cooper and Stanford, 2000). These neurons were also characterized by a high input resistance (712 Ϯ 150 M⍀) and spontaneous activity at rest (Fig.…”

“…1 A). This cellular subgroup corresponded to type C GP neurons described previously by Cooper and Stanford (2000).…”

Nitric oxide-active compounds modulate the intensity of glutamate-evoked responses in the globus pallidus of the rat

“…Interestingly, the modulation induced by NO-active drugs on the magnitude of GLU-induced neuronal responses was not necessarily linked to a direct, overt effect of the NO donor or the nNOS inhibitor on the spontaneous neuronal discharge activity. All recorded cells were characterized by spontaneous activity and probably they functionally represent projection neurons (Nambu and Llinas, 1997;Cooper and Stanford, 2000). Despite the different neuronal firing patterns (regularly and irregularly discharging units), already showed by previous studies (Ni et al, 2000;Sardo et al, 2002a), no patternrelated heterogeneous responses to pharmacological treatments were observed.…”