Predictors of cardiovascular response to smoked cocaine in humans

Sex differences in hippocampal β-adrenergic receptor subtypes drive retrieval, retention, and learning of cocaine-associated memories

Background

Drug seeking behavior occurs in response to environmental contexts and drug-associated cues. The presence of these pervasive stimuli impedes abstinence success. β-adrenergic receptors (β-ARs) have a long-standing historical implication in driving processes associated with contextual memories, including drug-associated memories in substance use disorders. However, sex differences in the role of β-adrenergic receptors in drug memories remain unknown.

Hypothesis

Prior reports indicate a selective role for β2-ARs in retrieval and retention of contextual drug memories in males, and substantial sex differences exist in the expression of β-ARs of male and female rats. Therefore, we hypothesized that there are sex differences in selective recruitment of β-ARs during different stages of memory encoding and retrieval.

Methods

The role of β-ARs in driving retrieval and learning of contextual cocaine memories was investigated using cocaine conditioned place preference (CPP) in adult male and female Sprague-Dawley rats. Rats were infused directly to the dorsal hippocampus with Propranolol (β1 and β2) or ICI-118,551 (β1) and/or Betaxolol (β2), immediately prior to testing (retrieval), or paired to each cocaine (10 mg/kp, IP) conditioning session (learning).

Results

In males, administration of either β1, β2, or combined β1 and β2-ARs before the initial CPP testing reduced the expression of a CPP compared to vehicle administration. In females, β2-ARs transiently decreased CPP memories, whereas β1 had long lasting but not immediate effects to decrease CPP memories. Additionally, β1 and combined β1 and β2-ARs had immediate and persistent effects to decrease CPP memory expression. DG Fos + neurons predicted cocaine CPP expression in males, whereas CA1 and CA3 Fos + neurons predicted cocaine CPP expression in females.

Conclusion

There are significant sex differences in the role of dorsal hippocampus β-ARs in the encoding and expression of cocaine conditioned place preference. Furthermore, sub regions of the dorsal hippocampus appear to activate differently between male and female rats during CPP. Therefore DG, CA3, and CA1 may have separate region- and sex-specific impacts on driving drug- associated, or context-associated cues.

Effect of long-term cocaine use on regional left ventricular function as determined by magnetic resonance imaging

This study examined left ventricular (LV) regional midwall circumferential strain by cardiac tagged magnetic resonance imaging in 32 long-term cocaine users and 14 nonusers. Most of the LV segmentations in the cocaine users had less average circumferential strain in the systolic and diastolic phases. The average diastolic strain in 5 ventricular segmentations was significantly less in the cocaine users (p<0.05). In conclusion, long-term cocaine use may be associated with regional LV dysfunction, especially diastolic dysfunction.

Long-term cocaine use is related to cardiac diastolic dysfunction in an African–American population in Baltimore, Maryland

BACKGROUND

Only limited studies have been done on the effects of long-term cocaine use on the human heart, and the results remain controversial. In this study, we examined and compared the diastolic function of non-cocaine users and chronic cocaine users to reveal the impact of long-term cocaine use on the human heart.

METHODS

Two-dimensional echocardiogram and pulsed Doppler transmitral blood flow pattern were obtained from 138 recruited study participants with different cocaine histories. The indices of cardiac structure and function were measured from the echocardiogram of each participant. Student's t-test was used to compare the average echocardiographic measurements of the non-cocaine user group and the cocaine user group. Multivariate regression analysis was deployed to eliminate the effects of age, gender, blood pressure, and HIV infection on the functional measurements of the two groups.

RESULTS

The cocaine user group had a significantly longer average deceleration time than did the non-cocaine user group (208.1 +/- 38.2 vs. 167.5 +/- 39.1 ms, P<0.001). A linear association existed between the deceleration time and the log-transformed duration of cocaine use (beta=0.00351, S.E.=0.00104, P=0.001). Cocaine users in this study were approximately five times more likely to have an elongated deceleration time (>200 ms) than were non-users (OR, 4.799; 95% CI, 1.000-23.044; P=0.05). No significant differences were observed in the other measured diastolic functional parameters, such as isovolumic ventricular relaxation time, E wave, A wave, and E/A ratio.

CONCLUSIONS

Long-term cocaine use is linked to decline in diastolic function.

Cardiovascular disorders associated with cocaine use: myths and truths

Cocaine produces a pattern of cardiovascular responses that are associated with apparent myocardial ischemia, arrhythmias, and other life-threatening complications in some individuals. Despite recent efforts to better understand the causes of cocaine-induced cardiovascular dysfunction, there remain a number of unanswered questions regarding the specific mechanisms by which cocaine elicits hemodynamic responses. This review will describe the actions of cocaine on the cardiovascular system and the evidence for the mechanisms by which cocaine elicits hemodynamic and pathologic responses in humans and animals. The emphasis will be on experimental data that provide the basis for our understanding of the mechanisms of cardiovascular toxicity associated with cocaine. More importantly, this review will identify several controversies regarding the causes of cocaine-induced cardiovascular toxicity that as yet are still debated. The evidence supporting these findings will be described. Finally, this review will outline the obvious deficits in our current concepts regarding the cardiovascular actions of cocaine in hope of encouraging additional studies on this grave problem in our society.

Acute aortic dissection related to crack cocaine

BACKGROUND

Although single case reports have described acute aortic dissection in relation to cocaine use, this condition is not widely recognized, and the features of cocaine-related aortic dissection have not been defined.

METHODS AND RESULTS

We reviewed all available hospital charts from 1981 to 2001 with the ICD-9 diagnosis of aortic dissection. Among the 38 cases of acute aortic dissection, 14 (37%) were related to cocaine use. Crack cocaine was smoked in 13 cases and powder cocaine was snorted in 1 case. The mean interval between cocaine use and the onset of symptoms was 12 hours (range, 0 to 24). Patients with cocaine-related dissection were much younger and more likely to undergo surgery compared with patients with aortic dissection without cocaine use. Most in the cocaine group were black, with a history of untreated hypertension. However, the two groups did not differ in other respects, including dissection type.

CONCLUSIONS

In an inner city population, acute aortic dissection in the setting of crack cocaine use is common, presumably as a consequence of abrupt, transient, severe hypertension and catecholamine release. This diagnosis should be considered in cocaine users with severe chest pain.

Intravenous cocaine increases plasma epinephrine and norepinephrine in humans

Cocaine has been shown to activate the sympathoadrenal system in both animal and human studies. Controlled human studies have found inconclusive results regarding whether acute cocaine treatment elevates plasma epinephrine and norepinephrine concentrations. The purpose of this study was to investigate whether commonly abused doses of cocaine increase plasma epinephrine and norepinephrine concentrations in humans, in a double-blind, placebo-controlled study. Five male cocaine users were given an intravenous injection of 0.46 mg/kg dose of cocaine or placebo, on two consecutive days. Plasma epinephrine and norepinephrine concentrations were significantly increased in response to cocaine injection compared to placebo. Peak plasma epinephrine and norepinephrine concentrations were reached 3 and 12 min after cocaine injection, respectively. While changes in epinephrine levels following cocaine were correlated with systolic blood pressure and heart rate changes, changes in plasma norepinephrine were correlated with diastolic blood pressure and heart rate changes following cocaine administration. These results suggest that plasma epinephrine and norepinephrine can be used as a measure for cocaine induced sympathoadrenal system activation.

Individual differences in the subjective response to smoked cocaine in humans

The individual variables that determine the effects of cocaine in humans are not well understood. In this study, we examined the relationship between the subjective response to cocaine and selected individual variables in cocaine-dependent participants. A single 0.4-mg/kg dose of smoked cocaine was received by 75 smoked cocaine users. The variables associated with increased subjective response to cocaine were male sex, presence of alcohol use, higher baseline Beck Depression Inventory (BDI) scores, and duration of cocaine use. The change in heart rate and diastolic blood pressure in response to cocaine delivery were also positively associated with the subjective response to cocaine. In contrast, body weight, years of schooling, and the change in the heart rate with the expectation of cocaine delivery were associated with a diminished subjective response to cocaine. The importance of these variables in maintaining the cocaine use behavior needs to be studied further.