The positive reinforcing effects of cocaine and opposite-sex social contact: roles of biological sex and estrus.

Rationale: Preclinical studies report that drug use and social contact mutually influence the reinforcing effects of one another. Most of these studies have used same-sex dyads exclusively, and the role of factors related to biological sex and hormonal fluctuations are not well understood.

Objectives: The purpose of this study was to examine the reinforcing effects of cocaine and social contact with an opposite-sex partner in male and female rats, and how these effects are modulated by ovarian hormones.

Treatment with dextroamphetamine decreases the reacquisition of cocaine self-administration: Consistency across social contexts.

Rationale: A return to cocaine use following abstinence frequently occurs in a social context, and the presence of other individuals using cocaine may contribute to the likelihood of use. Previous studies have reported that chronic d-amphetamine treatment decreases cocaine self-administration in laboratory animals and reduces a return to cocaine use following abstinence in humans.

Objective: The purpose of this study was to examine the effects of chronic d-amphetamine treatment on the reacquisition of cocaine use in rats self-administering cocaine in different social contexts.

"Tranq-dope" overdose and mortality: lethality induced by fentanyl and xylazine.

The recreational use of fentanyl in combination with xylazine (i.e., "tranq-dope") represents a rapidly emerging public health threat characterized by significant toxicity and mortality.

The effects of gonadal hormones on heroin Self-Administration in male gonadectomized rats.

Rationale: Previous studies have shown that gonadal hormones influence opioid self-administration in female rodents, but very few studies have examined these effects in male rodents.

Objectives: The purpose of this study was to examine the effects of chronic hormone treatment on intravenous heroin self-administration in gonadectomized male rats using both physiological and supraphysiological doses of testosterone, estradiol, or progesterone.

Methods: Gonadectomized male rats were surgically implanted with intravenous catheters and trained to self-administer heroin on a fixed ratio (FR1) schedule of reinforcement.

"Tranq-Dope" Overdose and Mortality: Lethality Induced by Fentanyl and Xylazine.

The recreational use of fentanyl in combination with xylazine (i.e., "tranq-dope") represents a rapidly emerging public health threat characterized by significant toxicity and mortality.

Response-contingent cocaine increases the reinforcing effectiveness of social contact.

Epidemiological studies report a high concordance rate of drug use within groups, suggesting an interplay between drug reinforcement and social cohesion. Preclinical studies reveal that (a) contingent access to a social partner increases cocaine intake and (b) experimenter-delivered cocaine increases the reinforcing effects of social contact. The purpose of this study was to determine if response-contingent cocaine increases the reinforcing effectiveness of social contact.