Physostigmine challenge before and after chronic cholinergic blockade in elderly volunteers

Aging and Clinical Pharmacology: Implications for Antidepressants

The elderly frequently have changes in pharmacokinetics, sensitivity to medications, homeostatic reserve (ability to tolerate physiological challenges), exposure to multiple medications, and adherence. All of these age-associated factors can potentially influence total exposure to medication, adverse effects, and subsequent treatment outcome. Most clinical trials are performed with healthy, younger adults. Extrapolating the results of these trials to the elderly may be inappropriate, particularly for the antidepressant treatment of depression. The authors review these age-associated differences and discuss their implications for antidepressant use in older adults.

Effects of acamprosate and scopolamine on the working memory of rats in a three-panel runway task

The aim of this study was to evaluate the effect of treatment with single (1x) and multiple (10x) doses of the anti-craving compound acamprosate (AC, calcium acetyl homotaurinate) on working memory in rats, using in a three-panel runway test. We measured tasks after the animals were treated with AC (500 mg/kg/d, i.p.); scopolamine (SC, 0.5 mg/kg/d, i.p.), a cholinergic muscarinic receptor antagonist; or both drugs concomitantly (ACSC), either for 1 day (1x) or daily for 10 consecutive days (10x). Neither 1x not 10x AC alone had a significant effect on working memory task performance, whereas treatment with SC alone had a significantly negative effect on the ability of the rats to complete the tasks. Rats receiving ACSC performed better than those receiving SC alone, making fewer errors and displaying shorter latency, similar to the performance of the control group. These observations support the hypothesis of an indirect involvement of AC in the cholinergic system.

Sexual diergism in rat hypothalamic-pituitary-adrenal axis responses to cholinergic stimulation and antagonism

The hypothalamic-pituitary-adrenal (HPA) axis has differential physiological activity in male and female animals (sexual diergism). Central cholinergic systems stimulate this endocrine axis. In the present study we investigated muscarinic and nicotinic cholinergic influences on HPA axis activity in male and female rats by pretreatment with selective cholinergic receptor antagonists followed by stimulation with physostigmine (PHYSO), an acetylcholinesterase inhibitor. Hormonal measures were plasma arginine vasopressin (AVP), adrenocorticotropic hormone (ACTH), and corticosterone (CORT). Male rats had significantly greater AVP and ACTH responses to PHYSO alone than did females. Scopolamine (SCOP) enhanced the AVP response to PHYSO to a greater extent in males than in females. In contrast, mecamylamine (MEC) enhanced the AVP response in females but decreased it in males. SCOP potentiated, and MEC inhibited, the stimulatory effect of PHYSO on ACTH in both sexes, but SCOP potentiation was greater in males, and MEC inhibition was greater in females. Absolute CORT increases following PHYSO were greater in females, but percent increases over baseline were greater in males. Similar to their effects on ACTH responses, MEC attenuated, and SCOP enhanced, CORT responses to PHYSO. These results suggest that cholinergic receptor subtypes may influence HPA axis activity differentially in male and female rats.