Analysis of body condition indices reveals different ecotypes of the Antillean manatee.

Assessing the body condition of wild animals is necessary to monitor the health of the population and is critical to defining a framework for conservation actions. Body condition indices (BCIs) are a non-invasive and relatively simple means to assess the health of individual animals, useful for addressing a wide variety of ecological, behavioral, and management questions. The Antillean manatee (Trichechus manatus manatus) is an endangered subspecies of the West Indian manatee, facing a wide variety of threats from mostly human-related origins. Our objective was to define specific BCIs for the subspecies that, coupled with additional health, genetic and demographic information, can be valuable to guide management decisions. Biometric measurements of 380 wild Antillean manatees captured in seven different locations within their range of distribution were obtained. From this information, we developed three BCIs (BCI1 = UG/SL, BCI2 = W/SL3, BCI3 = W/(SL*UG2)). Linear models and two-way ANCOVA tests showed significant differences of the BCIs among sexes and locations. Although our three BCIs are suitable for Antillean manatees, BCI1 is more practical as it does not require information about weight, which can be a metric logistically difficult to collect under particular circumstances. BCI1 was significantly different among environments, revealing that the phenotypic plasticity of the subspecies have originated at least two ecotypes-coastal marine and riverine-of Antillean manatees.

Short-term and long-term effects of diazepam on the memory for discrimination and generalization of scopolamine.

Benzodiazepines are among the most widely prescribed and misused psychopharmaceutical drugs. Although they are well-tolerated, they are also capable of producing amnestic effects similar to those observed after pharmacological or organic cholinergic dysfunction. To date, the effect of benzodiazepine diazepam on the memory for discrimination of anticholinergic drugs has not been reported. The aim of the present study was to analyze the immediate and long-term effects of diazepam on a drug discrimination task with scopolamine. Male Wistar rats were trained to discriminate between scopolamine and saline administration using a two-lever discrimination task. Once discrimination was acquired, the subjects were divided into three independent groups, (1) control, (2) diazepam, and (3) diazepam chronic administration (10 days). Subsequently, generalization curves for scopolamine were obtained. Additionally, the diazepam and control groups were revaluated after 90 days without having been given any other treatment. The results showed that diazepam produced a significant reduction in the generalization gradient for scopolamine, indicating an impairment of discrimination. The negative effect of diazepam persisted even 90 days after drug had been administered. Meanwhile, the previous administration of diazepam for 10 days totally abated the generalization curve and the general performance of the subjects. The results suggest that diazepam affects memory for the stimulus discrimination of anticholinergic drugs and does so persistently, which could be an important consideration during the treatment of amnesic patients with benzodiazepines.

Participation of the dorsal hippocampus in stimulus discrimination with scopolamine.

Stimulus discrimination is the capacity of an organism to differentiate between stimuli and emit associated responses. The administration of the muscarinic antagonist scopolamine can be used as a stimulus by mammals in a discrimination task. The present study analyzes the contribution of the hippocampus in scopolamine discrimination and generalization. Male Wistar rats, weighing 250-300 g at the beginning of the experiment, were trained to discriminate between scopolamine (1.0 mg/kg, i.p.) and saline administration using a two-lever operant task; rats had to respond differentially to each lever depending on the preceding drug or saline administration. Once stimulus control was attained, rats were tested with different scopolamine doses (0.0, 0.056, 0.091, 0.16, 0.31 and 1.0 mg/kg, i.p.) in order to obtain generalization curves. After generalization the rats were randomly assigned to hippocampal CA1 lesion or control groups. Hippocampus impairment produced a transient decrease in the capacity to discriminate between scopolamine and saline conditions; nonetheless, scopolamine correct responses were rapidly recovered after a few sessions and even maintained after 90 days. Correct responses for saline condition were never recovered. The generalization curve obtained after hippocampus lesion showed a response gradient severely flattened. Results suggest that the hippocampus participates as a neural system supporting the sensitivity to detect discrete changes in stimulus properties and relational memory, more than on the capacity to recall for simple associative responses.

Further evidence that the discriminative stimulus properties of indorenate are mediated by 5-HT 1A/1B/2C receptors.

Indorenate (5-methoxytryptamine beta-methylcarboxylate, INDO) is a serotonin (5-hydroxytryptamine, 5-HT) agonist that has affinity for 5-HT(1A/1B/2C) receptors. Unlike other anxiolytics such as 5-HT receptor agonists, INDO may not share tolerance or dependency with the benzodiazepine anxiolytics. It has been reported that the discriminative stimulus properties of 5-HT(1A/1B/2C) agonists, but not those of 5-HT(3/4) agonists, generalize to INDO. Therefore, the aim of the present study was to obtain further evidence on the differential involvement of 5-HT(1A/1B/2C) receptors in the discriminative stimulus properties of INDO by evaluating its interactions with antagonists of the 5-HT(1A), 5-HT(1B), 5-HT(2C), and 5-HT(3/4) receptor subtypes. Rats were trained to discriminate INDO from saline in a conditioned taste aversion paradigm. For Group D(+)S(-), administration of INDO signalled that saccharin flavour was followed by LiCl, while injection of vehicle signalled safe consumption of saccharin solution. Group D(-)S(+) had the contingencies reversed. After this training, rats had generalization tests where INDO administration was preceded by different doses of the following antagonists: WAY100635 (5-HT(1A)), NAN190 (5-HT(1A)), methiothepin (5-HT(1A/1B/2C)), GR127935 (5-HT(1B/1D)), ketanserin (5-HT(2A/2C)), ritanserin (5-HT(2C/2A)), mesulergine (5-HT(2C/2A)), metergoline (5-HT(2C/2A)), SB206553 (5-HT(2B/2C)), and tropisetron (5-HT(3/4)). In Group D(+)S(-), the order of potency to block the discriminative stimulus properties of INDO was WAY100635>ketanserin>ritanserin>GR127935>mesulergine congruent with SB206553>metergoline>methiothepin>NAN190, while in Group D(-)S(+), the order was WAY100635>GR127935>ketanserin>ritanserin>mesulergine congruent with SB206553>metergoline>methiothepin>NAN190. Tropisetron did not produce any alteration of the discriminative control by INDO. These results suggest that the discriminative signal of INDO is mediated by 5-HT(1A/2C/1B) receptors and that blockade of any of its components produces a degradation of its discriminative effects.

Full substitution of the discriminative cue of a 5-HT(1A/1B/2C) agonist with the combined administration of a 5-HT(1B/2C) and a 5-HT(1A) agonist.

The present study examined whether animals attend to the individual components of the cue produced by a drug that stimulates different 5-hydroxytryptamine (5-HT) receptor populations, using a drug discrimination task based on the conditioned taste aversion (CTA) procedure. The training drug was indorenate (5-methoxytryptamine beta-methylcarboxylate) (INDO) that has been described as a 5-HT(1A/2C/1B) agonist able to exert discriminative control in both operant and CTA procedures. The principal objective was to examine generalization with the combined administration of agonists for the different receptor sites that may mimic the mechanism of action of the training drug. Male Wistar rats, deprived of water, were trained to discriminate INDO from saline; during the drug trials, the administration of INDO preceded saccharin-LiCl pairings, while, during the saline trials, the administration of saline preceded the saccharin-saline pairings. In generalization tests, INDO, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT, a 5-HT(1A) agonist), 1-(3-trifluoromethylphenyl)piperazine (TFMPP, a 5-HT(1B) agonist), alpha-methyl-5-HT (a 5-HT(2C) agonist) or 2-methyl-5-HT (a 5-HT(3) agonist), were administered alone or in combination. The results showed that 8-OH-DPAT, TFMPP and alpha-methyl-5-HT produced dose-dependent generalization, up to 88% in the case of 8-OH-DPAT. The combined administration of the following pairs of drugs, 8-OH-DPAT+TFMPP or 8-OH-DPAT+ alpha-methyl-5-HT, at doses that produced only 15-55% generalization when administered alone, produced greater than 80% generalization to INDO. However, the single administration of 2-methyl-5-HT produced only saline-like responding and its combined administration with 8-OH-DPAT did not modify the generalization produced by the single administration of 8-OH-DPAT. These results suggest that animals attend to the individual components of the drug cue; in the case of INDO, which has three elements, each mediated by a different receptor subpopulation (5-HT(1A), 5-HT(1B) and 5-HT(2C) ), the separate stimulation of at least two receptor subpopulations was 'interpreted' by the subject as the presence of the training drug.

Discriminative stimulus properties of indorenate in a conditioned taste aversion paradigm.

Indorenate (5-methoxytryptamine beta-methylcarboxylate, INDO) is a serotonin (5-hydroxytryptamine, 5-HT) agonist that has affinity for 5-HT(1A/1B/2C) receptors. It possesses anxiolytic and antihypertensive actions mediated by 5-HT(1A) receptors and anorectic activity mediated by 5-HT(2C/1B) receptors. This study examined whether INDO may exert discriminative control using a conditioned taste aversion (CTA) paradigm, and whether differential participation of 5-HT receptor subtypes may be involved in its cue. Male Wistar rats trained to drink their daily water in a 30-min period were trained to discriminate INDO from saline. One group received the intraperitoneal administration of INDO (10.0 mg/kg) before saccharin-LiCl pairings; on alternate days, rats received saline before the saccharin-saline pairings (Group D(+)S(-)). The other group had the contingencies reversed (i.e., the administration of INDO preceded saccharin-saline pairings: Group D(-)S(+)). In two-bottle generalization tests (one bottle containing saccharin, the other plain water), the preference for saccharin was evaluated after different doses of INDO, [3H]-8-hydroxy-2-(di-N-propylamino)tetralin (8-OH-DPAT) (5-HT(1A)), buspirone (5-HT(1A)), RU24969 (5-HT(1A/1B)), TFMPP (5-HT(1B/2C)), MK212 (5-HT(2C)), alpha-Me-5-HT (5-HT(2C/2A)), 2-Me-5-HT (5-HT(3)) and cisapride (5-HT(4)). The results showed that INDO, RU24969, TFMPP, alpha-Me-5-HT and MK 212 produced a dose-dependent generalization; 8-OH-DPAT and buspirone produced only partial generalization, while 2-Me-5-HT and cisapride did not produce generalization. The results indicate that INDO administration may exert discriminative control over saccharin preference mediated mainly by 5-HT(1B/2C) receptors, but with an important contribution of 5-HT(1A) receptors.