Effects of sodium barbitone on learning and memory-storage of an appetitive and an aversive task

GABAergic modulation of neocortical long-term potentiation in the freely moving rat

Although the neocortex has generally been considered resistant to the induction of long-term potentiation (LTP), we have recently shown that LTP can be reliably induced in the freely moving rat provided that the stimulation sessions are spaced and repeated. Here, we report that the induction of LTP in this preparation can be modulated by both GABAergic agonism and antagonism. The delivery of stimulation trains in the presence of the GABA(A) agonist diazepam blocked the induction of neocortical LTP, while the GABA(A) antagonist picrotoxin slowed the development of potentiation. When animals that had previously received high-frequency stimulation combined with diazepam were repotentiated, they showed greater resistance to LTP induction than animals that had received diazepam alone. These data suggest that the inhibitory circuits themselves may have potentiated. The demonstration that diazepam blocks neocortical LTP provides further support for the notion that LTP plays a role in memory formation.

Sodium pentobarbital: sensory and associative effects in classical conditioning of the rabbit nictitating membrane response

Four experiments were conducted to determine the effects of sodium pentobarbital (0, 3, 9, and 15 mg/kg) on the acquisition of the rabbit's classically conditioned nictitating membrane response (NMR) and to determine the locus of the drug's effects on sensory, motor, associative, and nonassociative processes. In experiment 1, classical conditioning of the NMR was accomplished by pairing tone and light conditioned stimuli (CSs) with paraorbital shock as the unconditioned stimulus (US). The experiment revealed that pentobarbital retarded the acquisition of conditioned responses (CRs) to both tone and light CSs. Experiment 2, employing unpaired CS, UCS presentations, indicated small but significant drug effects on NMR base rate and nonassociative NMRs to the CS. Experiment 3 revealed no significant drug effect on the psychophysical functions relating UCS intensity to UCR frequency or amplitude, nor on the UCS intensity threshold for eliciting UCRs. On the other hand, in experiment 4, the drug significantly impaired CR frequency over an extended range of CS intensities and raised CS intensity threshold. It was concluded that pentobarbital's attenuation of CS intensity also operated to impair CR acquisition.