Retinal Input Induces Three Firing Patterns in Neurons of the Superficial Superior Colliculus of Neonatal Rats

Abstract

By using an in vitro isolated brain stem preparation, we recorded extracellular responses to electrical stimulation of the optic tract (OT) from 71 neurons in the superficial superior colliculus (SC) of neonatal rats (P1-13). At postnatal day 1 (P1), all tested neurons (n = 10) already received excitatory input from the retina. Sixty-nine (97%) superficial SC neurons of neonatal rats showed three response patterns to OT stimulation, which depended on stimulus intensity. A weak stimulus evoked only one spike that was caused by activation of non-N-methyl-D-aspartate (NMDA) glutamate receptors. A moderate stimulus elicited a short train (<250 ms) of spikes, which was induced by activation of both NMDA and non-NMDA receptors. A strong stimulus gave rise to a long train (>300 ms) of spikes, which was associated with additional activation of L-type high-threshold calcium channels. The long train firing pattern could also be induced either by temporal summation of retinal inputs or by blocking gamma-aminobutyric acid-A receptors. Because retinal ganglion cells show synchronous bursting activity before eye opening at P14, the retinotectal inputs appear to be sufficient to activate L-type calcium channels in the absence of pattern vision. Therefore activation of L-type calcium channels is likely to be an important source for calcium influx into SC neurons in neonatal rats.

An ex vivo preparation of the intact mouse vomeronasal organ and accessory olfactory bulb

“…However, the neurons and neural systems of these animals are functional under low perfusion rates and at low temperatures, unlike mammalian neural systems. Despite the experimental challenges associated with studying mammalian neurons, ex vivo methods continue to be developed to study mammalian sensory processing across brain regions and in intact CNS structures (Llinás and Mühlethaler, 1988; Mühlethaler et al, 1993; Lo and Mize, 1999; Ritter et al, 2000; Woodbury et al, 2001). Studying the AOS in vivo and ex vivo is particularly challenging due to the relative inaccessibility of the VNO and the long and delicate projections between the VNO and AOB.…”

Protein tyrosine phosphatases expression during development of mouse superior colliculus

“…As shown by Jena et al (1997), PTP1C is associated with synaptic vesicles and interacts directly with the vesicular protein synaptophysin, which suggests an involvement of PTP1C in synaptic transmission. Indeed, the expression profile of PTP1C in the superior colliculus correlates well with synaptogenesis, which starts approximately at P1 (Lo and Mize 1999). Furthermore, synaptophysin is up-regulated during neuronal development and maturation (Becher et al 1999a, b).…”

Modeling visual and auditory integration of barn owl superior colliculus with STDP

“…This is because physiological studies have shown the neural spikes are stochastic events. The spike trains are triggered short bursts of equal-amplitude spikes [15], [16]. As the stimuli repeated for simulaiton, the spike clusters are triggerred periodically.…”