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Biomedical subjects

S G Smith

Publications and source records attributed to S G Smith.

At least 109 records · Page 6Linked to original sources
PubMed1980

Maturation of the clock-timed gonadotropin release mechanism in hamsters: a key event in the pubertal process?

Gonadotropin secretion patterns were monitored in 10, 14 to 21-, and 35-day-old prepubertal female hamsters by RIA. Blood samples were obtained between 1500-1900 h to coincide with the time when the adult female hamster experiences a clock-timed surge in gonadotropin release. Before 16 days of age, the female hamster appears to exhibit a tonic pattern of gonadotropin release. On day 16 and thereafter, the female hamster exhibits a daily surge of gonadotropin release. Around the clock sampling (every 3 h) has shown that this cyclic pattern of gonadotropin release is not present at any time studied in female hamsters younger than 16 days of age, appears to be clock timed, and occurs at the same time of day as the proestrus surge in cyclic adults. The maturation of the clock timed gonadotropin release mechanism may indicate maturation of the reproductive control system, a key event in the pubertal process.

Animals↗
PubMed1979

Reinforcement with intragastric infusions of ethanol: blocking effect of FLA 57.

Suppression of oral intake of ethanol by FLA 57 has been reported for rats and was attributed to an inhibition of dopamine beta-hydroxylase. We have demonstrated the ability of FLA 57 (50 mg/kg, IP) to suppress bar-pressing for intragastric (IG) delivery of doses of ethanol (25 mg/kg). This indicates that the effect on oral intake of ethanol may not be attributed to a taste factor, e.g., a decreased palatability of the ethanol solution. The same dose of FLA 57 did not suppress responding for IG doses of sweet milk. Thus, there was not an impairment of appetitive behavior in general through some nonspecific depressant or toxic action. Furthermore, the primary reinforcing action of ethanol, when used to establish a buzzer as a conditioned reinforcer through repeated pairings, was blocked if FLA 57 was given before pairings. This was evidenced by a failure of such rats to bar-press above the baseline level in a later test of conditioned reinforcement, which contrasted with the increased responding seen for rats receiving saline instead of FLA 57 before ethanol. These data support the previous findings on oral ethanol and confirm that FLA 57 can impair the mechanism by which ethanol produces positive reinforcement in rats.

Animals↗
PubMed1978

Noradrenergic role in the self-administration of ethanol.

Involvement of noradrenergic and/or dopaminergic processes of the brain in self-administration behavior toward ethanol was assessed in rats allowed to lever-press for 25 mg/kg intragastric doses on a CRF schedule. Initial access to infusions of saline for establishing an operant baseline was followed by one 10-hr session on acquisition contingencies for ethanol and then one extinction session on saline. Prior to a reacquisition session, rats were treated with either (a) saline, (b) alpha-methyl-p-tyrosine (AMT; 225 mg/kg), (c) 1-phenyl-3-(2-thiazolyl)-2-thiourea (U-14,624; 600 mg/kg or 300 mg/kg), or (d) haloperidol (3.5 mg/kg). Only the saline-pretreated control group and the haloperidol-treated rats reacquired lever-press behavior. Groups treated in like fashion, but pressing for a sweet milk reinforcer, all showed reacquisition. Thus, the effects of AMT and U-14,624 are attributed to an inteference with the reinforcing effect of ethanol infusions. Brain levels of norepinephrine were depleted by both compounds, dopamine was depleted only by AMT, and serotonin was elevated by 600 mg/kg of U-14,624 but unaffected by 300 mg/kg. These results suggest that a cerebral noradrenergic system plays an important role in the reinforcing effect of ethanol without an involvement of dopaminergic systems.

Animals↗
PubMed1977

Alcohol-associated conditioned reinforcement.

Research was conducted to examine the ability of alcohol to impart conditioned reinforcement. Rats were allowed to self-administer solutions of either saline or alcohol (25, 50, and 100 mg/kg/infusion) by the intragastric route. Superimposed on the infusion interval was a buzzer (conditioned reinforcing stimulus). Tests during extinction revealed that conditioned reinforcement had been acquired. Results also indicated that as the paired unit dose was increased, potency of the conditioned reinforcer increased. In a second study, the lever-pressing response, which produced saline infusion and the buzzer, became available only subsequent to 5 sessions of pairing the buzzer with infusions of saline or alcohol. The results indicated that lever pressing increased with increasing unit dosage of alcohol infusions in prior pairings.

Animals↗