Giao B. Hang

Studies of striatal physiology and motor control have increasingly relied on the use of bacterial artificial chromosome (BAC) transgenic mice expressing fluorophores or other genes under the control of genetic regulatory elements for the dopamine D1 receptor (D1R) or dopamine D2 receptor (D2R). Three recent studies have compared wild-type, D1R, and D2R BAC transgenic mice, and found significant differences in physiology and behavior, calling into question the use of these mice in studies of normal circuit function. We repeated the behavioral portions of these studies in wild-type C57BL/6 mice and hemizygous Drd1a-td Tomato (D1-Tmt), Drd1a-eGFP (D1-GFP), and Drd2-eGFP (D2-GFP) mice backcrossed into the C57BL/6 background. Our three laboratories independently found that open-field locomotion, acute locomotor responses to cocaine (20 mg/kg), locomotor sensitization to 5 d of daily injections of cocaine (15 mg/kg) or amphetamine (3 mg/kg), cocaine (20 mg/kg) conditioned place preference, and active avoidance learning to paired light and footshock were indistinguishable in these four mouse lines. These results suggest that while it is crucial to screen new transgenic mouse lines for abnormal behavior and physiology, these BAC transgenic mouse lines remain extremely valuable tools for evaluating the cellular, synaptic, and circuit basis of striatal motor control and associative learning.

Neocortical neurons in vivo receive concurrent synaptic inputs from multiple sources, including feedforward, horizontal, and feedback pathways. Layer 2/3 of the visual cortex receives feedforward input from layer 4 and horizontal input from layer 2/3. Firing of the pyramidal neurons, which carries the output to higher cortical areas, depends critically on the interaction of these pathways. Here we examined synaptic integration of inputs from layer 4 and layer 2/3 in rat visual cortical slices. We found that the integration is sublinear and temporally asymmetric, with larger responses if layer 2/3 input preceded layer 4 input. The sublinearity depended on inhibition, and the asymmetry was largely attributable to the difference between the two inhibitory inputs. Interestingly, the asymmetric integration was specific to pyramidal neurons, and it strongly affected their spiking output. Thus via cortical inhibition, the temporal order of activation of layer 2/3 and layer 4 pathways can exert powerful control of cortical output during visual processing.

Studies of the midbrain phonation and somatic motor reactions were made in acute experiments on 51 Gecko gecko.The production of the reactions of phonation by stimulation (chemical and electric stimulation) of the midbrain had been much studied in birds and mammals.But studies on reptiles for example on Gecko gecko,appeared to be yet lacking.The present paper reports observations relating to this question.The writers have paid especial attention to the reactions of phonation as well as to somatie motor and vegetative reactions.The stimulation of the midbrain (optical lobes) in Gecko gecko caused phonation reactions which are similar to that of frightened phonation of the birds and roar of mammals accompanied with first dilatation later reduction of the pupil as well as certain somatic movements and tail swings.The results of stimulation of the midbrain were essentially the same before and after the cutting off the cerebrum.The site in the midbrain where stimulation elicited reactions of phonation is in the forth lateral region to the nucleus mesencephalicus lateralis.stimulation of points beyond this region extending 0.8-1.0mm in various directions elicits no phonation reactions but somatie movements.