No abstract

Chronic single neuronal recording techniques were applied to investigate the involvement of the medial prefrontal cortex (mPFC) during cocaine self-administration in the rat. Rats were trained to press a lever for cocaine under continuous reinforcement and fixed ratio schedules. Different patterns of phasic neuronal activity changes were found to be associated with lever-pressing for cocaine. The neuronal responses could be classified into five categories: 1) increases in neuronal firing before the lever press (15 out of 121 neurons, 12.4%); 2) decreases in neuronal firing before the lever press (13 neurons, 10.7%); 3) increases in neuronal firing after cocaine infusion (4 neurons, 3.3%); 4) decreases in neuronal firing after cocaine infusion (32 neurons, 26.4%); and 5) no alteration of neuronal activity throughout the self-administration session (67 neurons, 55.4%). The anticipatory responses, i.e., neuronal activity appearing before the lever press, were observed for both the continuous reinforcement and fixed ratio schedules. In a few cases, alteration of firing rate was not observed for the first lever press but appeared before subsequent lever presses in fixed ratio schedules. Eliminating cocaine abolished the inhibitory neuronal responses observed after lever press, suggesting that these inhibitory responses after cocaine self-administration were attributable to the pharmacologic effect of cocaine. The data provide initial electrophysiological evidence that the mPFC may play a role in mediating the task sequencing which leads to cocaine self-administration.

Brine deposited in Chaerhan salt lake belongs to the chloride type and can be simplified into the hexnary system Li+, Na+, K+, Mg2+, Ca2+, Cl––H2O. The known solubility data indicate that significant salting-in effects exist in its subsystems of KCl–LiCl–H2O and KCl–CaCl2–H2O, which inevitably affect the properties and solubility behavior of actual brine. In this work, the solubility behavior study and phase diagram determination are extended to the quaternary system of Li+, K+, and Ca2+∥Cl––H2O. The phase equilibrium data at 298.15 and 273.15 K are reported, and five solid species, including two double salts KCl·CaCl2 and LiCl·CaCl2·5H2O, are found. The salting-in effect is still exhibited in the Li+, K+, and Ca2+∥Cl––H2O system and results in a very high total salt content at invariant points; e.g., they are 59.08 and 46.93% at 298.15 and 273.15 K, respectively.