Elevated testosterone in females reveals a robust sex difference in altered androgen levels during chronic alcohol withdrawal.

The endocrine disruption associated with alcohol (ethanol) abuse in both males and females is widely recognized. Ethanol intoxication and withdrawal in males results in significant reductions in androgen levels. Less is known about female alcoholics, and because the changes in testosterone concentrations remain controversial, we systematically characterized changes in sex steroids after chronic ethanol exposure and withdrawal in both sexes. Testosterone and 17ß-estradiol concentrations were determined during chronic high intoxication, over a withdrawal time course, and following a period of abstinence using a genetic model of withdrawal vulnerability, the Withdrawal Seizure-Resistant (WSR) and -Prone (WSP) selected lines. In males, testosterone concentrations were significantly lower in intoxicated WSP mice after chronic ethanol exposure, and were dramatically and transiently reduced during the withdrawal period in both WSR and WSP lines. In contrast, testosterone levels were increased in intoxicated WSP females and in both WSR and WSP mice during withdrawal. Chronic ethanol exposure disrupted normal estrous cycling in WSP mice, associated with hyperandrogenemia while intoxicated. In abstinence, elevated testosterone was observed in both sexes but only in WSR mice. Estrogen levels were modestly reduced during withdrawal in both WSR and WSP lines, predominantly in males. These findings identify a mechanism based on altered androgen signaling that likely contributes to sex-specific responses during withdrawal. However, only WSR mice showed similar elevations in androgen long after withdrawal in both sexes, suggesting that genotype is an important determinant of steroid responses after abstinence. Increased androgen signaling in females as a consequence of chronic ethanol exposure may play an important and relatively uncharacterized role in sexually dimorphic responses to alcohol abuse.

Increase in matrix metalloproteinase-9 levels in the rat medial prefrontal cortex after cocaine reinstatement of conditioned place preference.

Recently we have shown that inhibition of matrix metalloproteinase (MMP) activity suppresses the reinstatement of cocaine-primed conditioned place preference (CPP) in rats. Here we explored whether cocaine-primed reinstatement was associated with increased activity of the gelatinases, MMP-2 or MMP-9, in the medial prefrontal cortex (mPFC) or dorsal hippocampus. Male Sprague-Dawley rats underwent training for cocaine-CPP followed by extinction sessions and either saline- or cocaine-priming injections. Cocaine-induced reinstatement produced significant increases in mPFC MMP-9 activity at 1, 3 and 24 hr after injection compared with saline controls. No changes in MMP-9 occurred in the hippocampus or in MMP-2 activity in either brain region. Also, no changes in mPFC MMP-9 activity were observed 1 hr after reinstatement in animals given no extinction sessions but equivalent time off in the home cage. Finally, MMP-3 protein levels were not different in either brain region at any of the three time points assessed. These results suggest that an elevation in MMP-9 activity in the mPFC may contribute to synaptic remodeling important for the reactivation of a cocaine memory, or alternatively, for the modification of a competing extinction memory during reinstatement.

Role of matrix metalloproteinases in the acquisition and reconsolidation of cocaine-induced conditioned place preference.

Persistent drug seeking/taking behavior involves the consolidation of memory. With each drug use, the memory may be reactivated and reconsolidated to maintain the original memory. During reactivation, the memory may become labile and susceptible to disruption; thus, molecules involved in plasticity should influence acquisition and/or reconsolidation. Recently, matrix metalloproteinases (MMPs) have been shown to influence neuronal plasticity, presumably by their regulation of extracellular matrix (ECM) molecules involved in synaptic reorganization during learning. We hypothesized that inhibition of MMP activity would impair the acquisition and/or reconsolidation of cocaine-conditioned place preference (CPP) in rats. Intracerebral ventricular (i.c.v.) microinjection of a broad spectrum MMP inhibitor, FN-439, prior to cocaine training suppressed acquisition of CPP and attenuated cocaine-primed reinstatement in extinguished animals. In a separate experiment, the cocaine memory was reactivated on two consecutive days with a cocaine priming injection. On these two days, artificial cerebral spinal fluid (aCSF) or FN-439 was administered either 30 min prior to or 1 min after cocaine-primed reinstatement sessions. Infusion of FN-439 partially impaired retrieval of the cocaine-associated context when given 30 min prior to cocaine. In both groups, however, FN-439 suppressed reinstatement compared with controls on the third consecutive test for cocaine-primed reinstatement, when no FN-439 was given. Control experiments demonstrated that two injections of FN-439 + cocaine given in the home cage, or of FN-439 + saline priming injections in the CPP chambers did not disrupt subsequent cocaine-primed reinstatement. These results show for the first time that (1) MMPs play a critical role in acquisition and reconsolidation of cocaine-induced CPP, and (2) rats demonstrate apparent disruption of reconsolidation by an MMP inhibitor after extinction and while they are under the influence of cocaine during reinstatement.

Low level lindane exposure alters extinction of conditioned fear in rats.

Gamma-hexachlorocyclohexane (lindane) is a pesticide with the potential to produce long-term effects on fear or anxiety due to its targeting of the GABA(A) receptor in the brain. Multiple chemical sensitivity (MCS) is a human condition that has been attributed to repeated chemical exposures, with pesticides heavily implicated in the initiation of MCS. The symptoms in MCS patients are wide ranging but prominent among these in a subset of patients is increased evoked panic responses. Drawing a parallel between these responses in MCS patients and a panic model in rats, these studies explored a potential animal model for MCS. The effects of repeated lindane exposure on conditioned fear behavior was examined in adult male Sprague-Dawley rats. Animals were administered vehicle or lindane (intraperitoneally) for either 3 days/week (1, 2 or 5mg) or 5 days/week (2mg) over 2 weeks, and 18 days later were examined for anxiety levels on an elevated plus-maze. One day later, animals were trained for fear conditioning to an odor conditioned stimulus (CS). Freezing behavior was measured 1 day later in the context where pairing occurred, and then for a total of 6 days in a different environment in which either no CS or the CS was presented. After a second 18-day period of no treatment, rats were again tested for their freezing response to the CS for 2 days. Lindane pretreatment did not alter elevated plus-maze performance, nor did it alter contextual freezing behavior. However, pretreatment with lindane decreased the extinction of fear conditioning to the CS such that freezing behavior in controls was significantly lower than in lindane-pretreated rats, and this effect persisted during testing 18 days later. The results indicate that repeated low-level lindane exposure may produce long-lasting changes in anxiety-related neural circuitry. This suggests that odor-triggered symptoms associated with an aversive event may persist in MCS patients because of the ability of some chemicals to alter fear or anxiety circuitry in the brain.