Intracerebroventricularly administered galanin does not alter operant reaction time or differentially reinforced high rate schedule operant responding in rats

Galanin and Cognition

Since the neuropeptide galanin’s discovery in 1983, information has accumulated that implicates it in a wide range of functions, including pain sensation, stress responses, appetite regulation, and learning and memory. This article reviews the evidence for specific functions of galanin in cognitive processes. Consistencies as well as gaps in the literature are organized around basic questions of methodology and theory. This review shows that although regularities are evident in the observed behavioral effects of galanin across several methods for measuring learning and memory, generalization from these findings is tempered with concerns about confounds and a restricted range of testing conditions. Furthermore, it is revealed that many noncognitive behavioral constructs that are relevant for assessing potential roles for galanin in cognition have not been thoroughly examined. The review concludes by laying out how future theory and experimental work can overcome these concerns and confidently define the nature of the association of galanin with particular cognitive constructs.

Galanin: a potential role in mesolimbic dopamine-mediated instrumental behavior

The involvement of the neuropeptide galanin in the consumption of the primary "commodities" of food and water is well established. However, the present review describes anatomical and behavioral evidence that suggests that galanin may also modulate ascending mesolimbic dopamine function and thereby play an inhibitory role in the systems by which instrumental behavior is energized toward acquiring primary commodities. General anatomical frameworks for this interaction are presented and future studies that could evaluate it are discussed.

Administration of the galanin antagonist M40 into lateral septum attenuates shock probe defensive burying behavior in rats

Galanin (GAL) has been implicated in modulating anxiety, although a precise role remains unclear. Previous studies revealed anxiolytic effects, anxiogenic effects, or no effect, depending on the test, brain region, route of drug administration and context. We have shown previously that microinjection of the GAL antagonist M40 into central amygdala blocked an anxiolytic response to acute stress on the elevated plus maze when rats were pretreated with yohimbine, suggesting an anxiolytic effect of GAL. By contrast, we also showed that microinjection of M40 into the lateral bed nucleus of the stria terminalis attenuated anxiety-like behavioral responses to stress on the plus maze and social interaction tests, implying an anxiogenic effect for GAL. The behavioral response to stress on both these tests is a reduction of an ongoing behavior (open-arm exploration or social interaction, respectively). To better understand the anxiety-modulating role of GAL, it is also important to ascertain its effect on a response that represents an activation rather than suppression of behavior. Thus, in this study, we investigated an active behavioral response to acute stress in rats, the shock-probe defensive burying response. Bilateral microinjections of M40 into lateral septum (LS), a region important to this response and innervated by GAL, dose-dependently decreased burying without affecting immobility. No change was seen in hindpaw withdrawal latency on a thermosensitivity assay, suggesting that the reduction in burying behavior was not attributable to changes in cutaneous pain sensitivity. These results indicate that in LS, GAL facilitates the active anxiety-like behavioral response on the defensive burying test, similar to its facilitatory effect on anxiety-like stress-induced suppression of behavior in the lateral bed nucleus. These results highlight the fact that, rather than a unified system-like role in modulating anxiety, the effects of GAL can be either facilitating or attenuating, and are region-specific, context-specific and response-specific.

Assessment of new functional roles for galanin in the CNS

There is considerable evidence that galanin plays an important role in food intake, nociception, stress reactivity, sexual behavior, and learning. However, its involvement in other important behavioral processes, especially higher cognition, has not been systematically investigated. This review summarizes our recent efforts to explore the role of galanin in executive processes as well as in fundamental motivational and motor productive processes that are essential to the behavioral assessment of cognitive constructs in rodents. Our work points to a role in reward processes and physiological water balance regulation, and argues against a role for galanin in fine motor production and maintenance, simple visual discrimination, and perseveration.

Intracerebroventricular administration of galanin decreases free water intake and operant water reinforcer efficacy in water-restricted rats

The 29/30 amino acid neuropeptide galanin coexists with vasopressin in the hypothalamus and has been shown to inhibit the actions of vasopressin and aldosterone, suggesting an inhibitory role for galanin in physiological water retention mechanisms and water seeking and water consumption behavior. Little work, however, has examined a role for galanin in water intake regulation. Furthermore, many experiments that have reported galanin-induced impairments in the performance of tasks thought to measure learning and memory have used water restriction routines and water reinforcers to maintain responding. Therefore, the present study examined the effects of intracerebroventricularly administered galanin (5.0-20.0 microg/5 microl) on free water consumption during a 10 min test session and a follow up open field exploration, an operant progressive ratio (PR) schedule, a test used to assess reinforcer strength, and an operant fixed time schedule (FT 20) in 23.5h water restricted rats. Finally, in an additional experiment that was designed to simulate the effects of a galanin-induced decrease in water reinforcer efficacy, the rats were allowed access to water prior to testing in an operant delayed non-matching to position (DNMTP) task. A galanin-induced decrease in water consumption was observed in both the free access test and the FT 20 at the 20 microg dose, but no significant galanin-induced alterations in open field behavior. A decrease in responses emitted and rewards received was observed on the PR schedule at the 5, 10, and 20 microg doses. Pre-session access to water significantly reduced the number of trials per session in the DNMTP but did not reduce accuracy. This study is the first to observe a galanin-induced reduction in water intake and reinforced operant behavior, and suggests that galanin may play a role in regulating water intake and reinforcement. However, the present data also suggest that DNMTP choice accuracy deficits observed previously cannot be attributed to a galanin-induced change in reinforcer efficacy.