The discriminability of apsirin in arthritic and nonarthritic rats

What Is It Like to Be a Bass? Red Herrings, Fish Pain and the Study of Animal Sentience

Debates around fishes' ability to feel pain concern sentience: do reactions to tissue damage indicate evaluative consciousness (conscious affect), or mere nociception? Thanks to Braithwaite's discovery of trout nociceptors, and concerns that current practices could compromise welfare in countless fish, this issue's importance is beyond dispute. However, nociceptors are merely necessary, not sufficient, for true pain, and many measures held to indicate sentience have the same problem. The question of whether fish feel pain - or indeed anything at all - therefore stimulates sometimes polarized debate. Here, we try to bridge the divide. After reviewing key consciousness concepts, we identify "red herring" measures that should not be used to infer sentience because also present in non-sentient organisms, notably those lacking nervous systems, like plants and protozoa (P); spines disconnected from brains (S); decerebrate mammals and birds (D); and humans in unaware states (U). These "S.P.U.D. subjects" can show approach/withdrawal; react with apparent emotion; change their reactivity with food deprivation or analgesia; discriminate between stimuli; display Pavlovian learning, including some forms of trace conditioning; and even learn simple instrumental responses. Consequently, none of these responses are good indicators of sentience. Potentially more valid are aspects of working memory, operant conditioning, the self-report of state, and forms of higher order cognition. We suggest new experiments on humans to test these hypotheses, as well as modifications to tests for "mental time travel" and self-awareness (e.g., mirror self-recognition) that could allow these to now probe sentience (since currently they reflect perceptual rather than evaluative, affective aspects of consciousness). Because "bullet-proof" neurological and behavioral indicators of sentience are thus still lacking, agnosticism about fish sentience remains widespread. To end, we address how to balance such doubts with welfare protection, discussing concerns raised by key skeptics in this debate. Overall, we celebrate the rigorous evidential standards required by those unconvinced that fish are sentient; laud the compassion and ethical rigor shown by those advocating for welfare protections; and seek to show how precautionary principles still support protecting fish from physical harm.

Depression during the menopause transition: impact on quality of life, social adjustment, and disability

The impact of depression on quality of life (QOL) and social support has neither been well characterized in clinical samples of women with perimenopausal depression (PMD) nor have the relative contributions of depression and other menopausal symptoms (e.g., hot flushes) to declining QOL been clarified. In this study, we compared QOL measures, social support, and functional disability in PMD and non-depressed perimenopausal women. We evaluated women aged 40-60 years who presented with menstrual cycle irregularity, elevated plasma FSH levels, and met criteria for perimenopause. A structured clinical interview was administered to determine the presence or absence of major and minor depression. Outcome measures included the Quality of Life Enjoyment Scale Questionnaire, the Sheehan Disability Scale, the Global Assessment of Functioning, the Social Adjustment Scale, and the Duke Social Support Index. Kruskal-Wallis tests and ANOVAs were used to compare outcome measures. Ninety women with PMD and 51 control women participated in this study. Women with PMD reported significantly decreased QOL, social support, and adjustment and increased disability compared with non-depressed perimenopausal women. Neither perimenopausal reproductive status alone nor the presence of hot flushes had a significant negative impact on QOL measures. PMD is accompanied by significant reductions in QOL, social support, and disability similar to depression in women at other stages of life. PMD may also contribute to decreased QOL in community- or clinic-based samples of perimenopausal women. It remains unclear whether the clinical characteristics we identified reflect pre-existing risk factors for depression during the perimenopause or the effects of a current depression. Future clinical and treatment studies in perimenopausal women should distinguish depressed women when outcome measures include QOL.

The application of conditioning paradigms in the measurement of pain

Pain is a private experience that involves both sensory and emotional components. Animal studies of pain can only be inferred by their responses, and therefore the measurement of reflexive responses dominates the pain literature for nearly a century. It has been argued that although reflexive responses are important to unveil the sensory nature of pain in organisms, pain affect is equally important but largely ignored in pain studies primarily due to the lack of validated animal models. One strategy to begin to understand pain affect is to use conditioning principles to indirectly reveal the affective condition of pain. This review critically analyzed several procedures that are thought to measure affective learning of pain. The procedures regarding the current knowledge, the applications, and their advantages and disadvantages in pain research are discussed. It is proposed that these procedures should be combined with traditional reflex-based pain measurements in future studies of pain, which could greatly benefit both the understanding of neural underpinnings of pain and preclinical assessment of novel analgesics.

Using drug-discrimination techniques to study the abuse-related effects of psychoactive drugs in rats

Drug-discrimination (DD) techniques can be used to study abuse-related effects by establishing the interoceptive effects of a training drug (e.g., cocaine) as a cue for performing a specific operant response (e.g., lever pressing reinforced by food). During training with this protocol, pressing one lever is reinforced when the training drug is injected before the start of the session, and responding on a second lever is reinforced when vehicle is injected before the session. Lever choice during test sessions can then be used as an indication of whether a novel drug has effects similar to the training drug, or whether a potential therapeutic alters the effects of the training drug. Although training can be lengthy (up to several months), the pharmacological specificity of DD procedures make them a perfect complement to other techniques used to study drug-abuse phenomena, such as intravenous self-administration and conditioned place-preference procedures.

Drug discrimination in neurobiology

Areas of neurobiological interest are identified towards which drug discrimination (DD) studies have made important contributions. DD allows ligand actions to be analyzed at the whole organism level, with a neurobiological specificity that is exquisite and often unrivalled. DD analyses have thus been made of a vast array of CNS agents acting on receptors, enzymes, or ion channels, including most drugs of abuse. DD uniquely offers access to the study of subjective drug effects in animals, using a methodology that also is transposable to humans and has generated unprecedented models of pathology (e.g., chronic pain, opiate addiction). Parametric studies of such independent variables as training dose and reinforcement provide refined insights into the dynamic psychophysiological mechanisms of both drug effects and behavior. Three different mechanisms have been identified by which discriminative, and perhaps other behaviors, can come about. DD also is superbly sensitive to small, partial activation of molecular substrates; this has enabled DD analyses to pioneer the unravelling of molecular mechanisms of drug action (attributing, f.ex., LSD's particular subjective effects to an unusual, partial activation of 5-HT, and perhaps other receptors). DD has both oriented and served as a tool to conduct drug discovery research (e.g., pirenperone-risperidone, loperamide). The DD response arguably constitutes a quantal, rather than graded, variable, and as such allows a comprehension of molecular, pharmacological, and behavioral mechanisms that would have been otherwise inaccessible. Perhaps most important are the following further contributions. One is the notion that particular, different levels of receptor activation are associated with qualities of neurobiological actions that also differ and are unique, this notion arguably constituting the most significant addition to affinity and intrinsic activity since the earliest theoretical conceptions of molecular pharmacology. Another contribution consists of studies that render redundant the notion of tolerance and identify fundamental mechanisms of signal transduction; these mechanisms account for apparent tolerance, dependence, addiction, and sensitization, and appear to operate ubiquitously in a bewildering array of biological systems.

State-dependent stimulus control: cueing attributes of ethanol "hangover" in rats

In Experiment 1, twelve Sprague-Dawley rats were trained in a two-choice food-reinforced drug discrimination task (10-min sessions) using the state-dependent interoceptive stimulus attributes of ethanol's (ETOH) delayed or rebound effects (EDE) versus "normal" basal homeostasis. Rats were injected with either 4 g/kg ETOH or equivalent volumes of saline (SAL) 18 hr before the sessions. Each rat was injected with an additional 1 ml/kg injection of SAL 15 min before the sessions. EDE training sessions were always followed by a "day off." SAL sessions were conducted between 36-96 hr after an EDE training session. Rats demonstrated > 90% discriminative accuracy. Test sessions showed a time-dependent, cyclic, return from the experimental "hangover" state to the "normal" state, by 48 hr. The acute (immediate) effects of ETOH and chlordiazepoxide (0.75 g/kg or 0.18 mg/kg, respectively; @15 min) did not cross-generalize with the "hangover" state. Both these low-dose ETOH and chlordiazepoxide pretreatments blocked the stimulus attributes of "hangover." All subjects responded on the EDE-appropriate lever at 5.6 mg/kg pentylenetetrazole and exhibited an increase in susceptibility to clonic seizures. In Experiment 2 blood alcohol concentration kinetics functions were quantified in three groups (n = 8/group) of age-matched cohorts to Experiment 1 subjects (2, 3, and 4 g/kg ETOH) using a head-space gas chromatographic technique. The training stimulus state associated with 4 g/kg, at 18 hr postinjection intervals, in Experiment 1, did not produce any chromatogram peaks for ETOH or any its active metabolite (acetaldehyde, acetone, nor methanol).(ABSTRACT TRUNCATED AT 250 WORDS)

Discriminative stimulus control with imipramine: transfer to other anti-depressants

Discriminative stimulus control with the tricyclic anti-depressant imipramine was attempted in three groups of rats; two of which were subjected to artificially stressful conditions. Only the unstressed group were shown capable of discriminating between the stimulus properties of intraperitoneal 10 mg/kg imipramine and saline in a two-lever, food-motivated operant task. Discriminative performance with decreasing doses of imipramine was shown to be dose-responsive. The ability to discriminate the interoceptive cue produced by imipramine was observed to transfer to a 10 mg/kg dose of both amitriptyline and desmethylimipramine. The results suggest a common tricyclic anti-depressant cueing property.

Copper salicylate as an anti-inflammatory and analgesic agent in arthritic rats

Recent research indicates that endogenous copper is involved in anti-inflammatory and tissue repair processes. Of interest also is the analgesic efficacy of Cu complexes, since rheumatoid arthritis and similar inflammatory conditions are extremely painful. In pilot experiments, arthritic rats failed to increase voluntarily their rate of drinking a 5 mg/ml solution of copper salicylate (Cu Sal). The data from the experiment reported here showed that a forced oral dose of Cu Sal calculated at 200 mg/kg body weight significantly reduced sensitivity to mechanical pressure in less than 30 minutes but more than 15 minutes. The analgesic effect of the Cu Sal was greater for arthritic than for non-arthritic rats, suggesting that two types of analgesia are involved. First, it produces a direct analgesic effect which works irrespective of the presence of inflammation. Second, it appears to have an indirect analgesic effect due to reduction of inflammatory hyperalgesia. It was also found that Cu Sal administered orally reduces inflammation in rats with adjuvant arthritis. In summary, the results from this experiment demonstrate that Cu Sal has specific and general analgesic properties and anti-inflammatory potential.

Effects of naloxone on the self-stimulation behavior of the postero-lateral area of the hypothalamus in rats--influence of procedural conditions

Rats exhibiting self-stimulation behavior through chronic electrodes implanted in the posterolateral part of the hypothalamus were subcutaneously injected with low doses (0.003-0.3 mg/kg) of naloxone. The animals were allowed to self-regulate the duration of rewarding brain stimulation. It was found that naloxone increases the duration of self-stimulation in rats in which the brain stimulation has previously been associated with footshock. Vehicle injections or injections of naloxone in rats that had not received footshock prior to testing, did not modify self-stimulation behavior. It is suggested that naloxone may facilitate an aversive central component of the brain stimulation; the conditioned rats therefore increased the duration of brain stimulation to compensate for this negative process.

Stimulus properties of antidepressants in the rat

Various doses of bupropion HCl (Wellbatrin) (5, 10, and 20 mg/kg), a new phenylaminoketone antidepressant, were employed as cues in a two-lever operant discrimination from saline control injections in rats on an FR10 schedule of food reinforcement. Subjects reached and maintained a high level of discrimination in the O vs 20 mg/kg bupropion stimulus condition but not at the lower doses. In generalization testing, the following compounds produced dose-related responding on the bupropion lever: viloxazine, nomifensine, caffeine, d-amphetamine, cocaine, methylphenidate, and benzylpiperazine. Drugs that failed to show dose-related generalization included phenethylamine, thyrotropin-releasing hormone, imipramine, nortriptyline, amitriptyline, desipramine, mianserin, chlordiazepoxide, diazepam, scopolamine, phenobarbital, and morphine. With the important exception of viloxazine, the generalization profile of bupropion seems to reflect its previously reported locomotor stimulant effects in the rat rather than its antidepressant activity and suggests that species differences exist between man and rat with regard to the pharmacologic activity of this new antidepressant.