Chemoarchitecture of GABAergic neurons in the ferret superior colliculus

Abstract

gamma-Aminobutyric acid (GABA)ergic neurons are thought to play a key role both in visual processing and in the complex sensory-motor transformations that take place in the mammalian superior colliculus. To understand the organization of GABAergic neurons in the ferret superior colliculus, we applied antisera to several markers of GABAergic function, including GABA, two isoforms of its synthetic enzyme glutamic acid decarboxylase (GAD-65 and GAD-67), and the GABA transporter, GAT-1. We also applied antisera to several calcium binding proteins (calbindin [CB], calretinin [CR], and parvalbumin [PV]) and neuronal nitric oxide synthase (NOS), chemical markers that colocalize with GABA in some areas of the central nervous system. The distribution of GABAergic neurons in the ferret is similar to that of other mammalian species. GABAergic neurons in the ferret superior colliculus were small, morphologically diverse, and widely distributed throughout all layers of the colliculus. As has been shown in other mammalian species, neurons expressing PV, CB, CR, and NOS were differentially distributed in layers and patches throughout the ferret colliculus. None of these markers, however, showed a distribution that mirrored that of GABAergic neurons. Furthermore, few GABAergic neurons colocalized these neurochemical markers. Only 14% of GABAergic neurons in the superficial layers and 18% of neurons in the deeper layers colocalized PV, 14% of GABAergic neurons in the superficial layers and 10% in the deeper layers colocalized CB, and only 1% of GABAergic neurons in both the superficial and deep layers colocalized nitric oxide synthase. Thus, the arrangement of GABAergic neurons in the ferret superior colliculus is broadly distributed and is distinct from other recognized organizational patterns in the superior colliculus.

Competitive Stimulus Interactions within Single Response Fields of Superior Colliculus Neurons

“…Presenting two stimuli in succession, within single RFs of superficial layer SC neurons, results in a suppressed response compared with when one stimulus is presented alone (Rizzolatti et al, 1973(Rizzolatti et al, , 1974Wurtz et al, 1980). Anatomical evidence reveals GABA neurons distributed uniformly throughout the SC (Mize, 1992;Behan et al, 2002). The present results demonstrate short-range competitive interactions influencing SC neurons.…”

Rapid modifications in calretinin immunostaining in the deep layers of the superior colliculus after unilateral cochlear ablation

“…The pattern of CR-immunostaining in the SC described in the present study was in agreement with that reported previously (Behan et al, 2002). In the superficial layers, CR-immunostaining consisted of heavily immunostained fibers and terminals as well as a few immunostained somata that were, in the majority of the cases, lightly immunostained ( Fig.…”

Intralaminar and Interlaminar Activity within the Rodent Superior Colliculus Visualized with Voltage Imaging

“…Since electrical activity in the SC is regulated by GABA (Chevalier et al, 1985; Chevalier and Deniau, 1990; Hall and Lee, 1993; Lee et al, 2001, 2007; Behan et al, 2002; Kaneda et al, 2008; Isa and Hall, 2009), we tested the actions of two GABA A receptor antagonists, bicuculline (50 μ m) and gabazine (SR95531, 5 μ m) (bicuculline and gabazine were used interchangeably and the results combined). These drugs generally increased the amplitude of optical signals, but had the greatest effects on after-depolarizations (Fig.…”