RESUMEN
Screening compounds for in vivo activity can be used as a first step to identify candidates that may be developed into pharmacological agents. We developed a novel nanoinjection/electrophysiology assay that allows the detection of bioactive modulatory effects of compounds on the function of a neuronal circuit that mediates the escape response in Drosophila melanogaster. Our in vivo assay, which uses the Drosophila Giant Fiber System (GFS, Figure 1) allows screening of different types of compounds, such as small molecules or peptides, and requires only minimal quantities to elicit an effect. In addition, the Drosophila GFS offers a large variety of potential molecular targets on neurons or muscles. The Giant Fibers (GFs) synapse electrically (Gap Junctions) as well as chemically (cholinergic) onto a Peripheral Synapsing Interneuron (PSI) and the Tergo Trochanteral Muscle neuron (TTMn. The PSI to DLMn (Dorsal Longitudinal Muscle neuron) connection is dependent on Dα7 nicotinic acetylcholine receptors (nAChRs). Finally, the neuromuscular junctions (NMJ) of the TTMn and the DLMn with the jump (TTM) and flight muscles (DLM) are glutamatergic. Here, we demonstrate how to inject nanoliter quantities of a compound, while obtaining electrophysiological intracellular recordings from the Giant Fiber System and how to monitor the effects of the compound on the function of this circuit. We show specificity of the assay with methyllycaconitine citrate (MLA), a nAChR antagonist, which disrupts the PSI to DLMn connection but not the GF to TTMn connection or the function of the NMJ at the jump or flight muscles. Before beginning this video it is critical that you carefully watch and become familiar with the JoVE video titled "Electrophysiological Recordings from the Giant Fiber Pathway of D. melanogaster" from Augustin et al, as the video presented here is intended as an expansion to this existing technique. Here we use the electrophysiological recordings method and focus in detail only on the addition of the paired nanoinjections and monitoring technique.
Asunto(s)
Drosophila melanogaster/fisiología , Evaluación Preclínica de Medicamentos/métodos , Nanotecnología/métodos , Fibras Nerviosas/efectos de los fármacos , Fibras Nerviosas/fisiología , Aconitina/administración & dosificación , Aconitina/análogos & derivados , Animales , Citratos/administración & dosificación , Insecticidas , Antagonistas Nicotínicos/administración & dosificaciónRESUMEN
Adolescent smoking is associated with auditory-cognitive deficits and structural alterations to auditory thalamocortical systems, suggesting that higher auditory function is vulnerable to nicotine exposure during adolescence. Although nicotinic acetylcholine receptors (nAChRs) regulate thalamocortical processing in adults, it is not known whether they regulate processing at earlier ages since their expression pattern changes throughout postnatal development. Here we investigate nicotinic regulation of tone-evoked current source density (CSD) profiles in mouse primary auditory cortex from just after hearing onset until adulthood. At the youngest ages, systemic nicotine did not affect CSD profiles. However, beginning in early adolescence nicotine enhanced characteristic frequency (CF)-evoked responses in layers 2-4 by enhancing thalamocortical, early intracortical, and late intracortical response components. Nicotinic responsiveness developed rapidly and peaked over the course of adolescence, then declined thereafter. Generally, responsiveness in females developed more quickly, peaked earlier, and declined more abruptly and fully than in males. In contrast to the enhancement of CF-evoked responses, nicotine suppressed shorter-latency intracortical responses to spectrally distant (non-CF) stimuli while enhancing longer-latency responses. Intracortical infusion of nAChR antagonists showed that enhancement of CF-evoked intracortical processing involves α4ß2*, but not α7, nAChRs, whereas both receptor subtypes regulate non-CF-evoked late intracortical responses. Notably, antagonist effects in females implied regulation by endogenous acetylcholine. Thus, nicotinic regulation of cortical processing varies with age and sex, with peak effects during adolescence that may contribute to the vulnerability of adolescents to smoking.
Asunto(s)
Estimulación Acústica/métodos , Corteza Auditiva/fisiología , Potenciales Evocados Auditivos/fisiología , Nicotina/administración & dosificación , Factores de Edad , Animales , Corteza Auditiva/efectos de los fármacos , Potenciales Evocados Auditivos/efectos de los fármacos , Femenino , Inyecciones Intraventriculares , Masculino , Ratones , Antagonistas Nicotínicos/administración & dosificación , Receptores Nicotínicos/fisiología , Receptor Nicotínico de Acetilcolina alfa 7Asunto(s)
Antidepresivos/uso terapéutico , Ensayos Clínicos Fase III como Asunto , Trastorno Depresivo Mayor/tratamiento farmacológico , Mecamilamina/uso terapéutico , Antagonistas Nicotínicos/uso terapéutico , Animales , Antidepresivos/administración & dosificación , Antidepresivos/química , Antidepresivos/economía , Antidepresivos/farmacología , Citalopram/administración & dosificación , Citalopram/uso terapéutico , Trastorno Depresivo Mayor/economía , Método Doble Ciego , Evaluación Preclínica de Medicamentos , Quimioterapia Combinada , Humanos , Mecamilamina/administración & dosificación , Mecamilamina/química , Mecamilamina/farmacología , Estructura Molecular , Estudios Multicéntricos como Asunto , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/química , Antagonistas Nicotínicos/farmacología , Selección de Paciente , Ensayos Clínicos Controlados Aleatorios como Asunto , Receptores Nicotínicos/efectos de los fármacos , Receptores Nicotínicos/fisiología , Inhibidores Selectivos de la Recaptación de Serotonina/administración & dosificación , Inhibidores Selectivos de la Recaptación de Serotonina/uso terapéutico , EstereoisomerismoRESUMEN
Alcohol and nicotine (in the form of tobacco) are 2 commonly used recreational drugs and studies show a high correlation between tobacco use and alcohol consumption. In the present study, using C57BL/6J mice, we investigated the ability of mecamylamine (a nicotinic antagonist) to reduce alcohol consumption and alcohol preference with free 24-hour access using a 2-bottle choice test drinking procedure. Male C57BL/6J mice were individually housed and acclimatized to 10% alcohol. Immediately following the last day of alcohol acclimatization, the mice (n = 5/group) received subcutaneous injections of mecamylamine (0.5, 1 and 2 mg/kg) or saline consisting of either intermittent (3 injections given every other day) or daily (injections on all 5 days) exposures. Fluid consumption (alcohol and water) was recorded daily. The results showed that mecamylamine significantly reduced alcohol consumption and alcohol preference in both phases of intermittent and daily drug exposures, while the total fluid consumption was unchanged. These results provide further support that mecamylamine is effective in reducing alcohol consumption and preference, and nicotinic-receptor-based drugs could further be explored as potential treatments for alcoholism.
Asunto(s)
Consumo de Bebidas Alcohólicas/tratamiento farmacológico , Conducta de Elección/efectos de los fármacos , Mecamilamina/farmacología , Antagonistas Nicotínicos/farmacología , Animales , Modelos Animales de Enfermedad , Ingestión de Líquidos/efectos de los fármacos , Evaluación Preclínica de Medicamentos , Masculino , Mecamilamina/administración & dosificación , Ratones , Ratones Endogámicos C57BL , Antagonistas Nicotínicos/administración & dosificaciónRESUMEN
Central thalamus has extensive connections with basal ganglia and frontal cortex that are thought to play a critical role in sensory-guided goal-directed behavior. Central thalamic activity is influenced by cholinergic projections from mesopontine nuclei. To elucidate this function we trained rats to respond to lights in a reaction time (RT) task and compared effects of muscarinic (2.4, 7.3, 22 nmol scopolamine) and nicotinic (5.4, 16, 49, 98 nmol mecamylamine) antagonists with the GABA(A) agonist muscimol (0.1, 0.3, 1.0 nmol) in central thalamus. We compared this with subcutaneous (systemic) effects of mecamylamine (3.2, 9.7, 29 micromol/kg) and scopolamine (0.03, 0.09, 0.26 micromol/kg). Subcutaneous scopolamine increased omissions (failure to respond within a 3-s response window) at the highest dose tested. Subcutaneous mecamylamine increased omissions at the highest dose tested while impairing RT and per cent correct at lower doses. Intrathalamic injections of muscimol and mecamylamine decreased per cent correct at doses that did not affect omissions or RT. Intrathalamic scopolamine increased omissions and RT at doses that had little effect on per cent correct. Anatomical controls indicated that the effects of mecamylamine were localized in central thalamus and those of scopolamine were not. Drug effects did not interact with attention-demanding manipulations of stimulus duration, proximity of stimulus and response locations, or stimulus array size. These results are consistent with the hypothesis that central thalamus mediates decisional processes linking sensory stimuli with actions, downstream from systems that detect sensory signals. They also provide evidence that this function is specifically influenced by nicotinic cholinergic receptors.
Asunto(s)
Antagonistas Colinérgicos/farmacología , Percepción Espacial/fisiología , Tálamo/efectos de los fármacos , Tálamo/fisiología , Percepción Visual/fisiología , Animales , Conducta Animal/efectos de los fármacos , Conducta Animal/efectos de la radiación , Conducta de Elección/fisiología , Antagonistas Colinérgicos/administración & dosificación , Relación Dosis-Respuesta a Droga , Combinación de Medicamentos , Agonistas del GABA/administración & dosificación , Agonistas del GABA/farmacología , Inyecciones , Inyecciones Subcutáneas , Luz , Masculino , Mecamilamina/administración & dosificación , Mecamilamina/farmacología , Muscimol/administración & dosificación , Muscimol/farmacología , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/farmacología , Ratas , Ratas Long-Evans , Tiempo de Reacción/efectos de los fármacos , Escopolamina/administración & dosificación , Escopolamina/farmacología , Tálamo/efectos de la radiaciónRESUMEN
5alpha-cardenolides isolated from Kanahia laniflora are inhibitors of muscle-type nicotinic acetylcholine receptors expressed in TE671 cells with IC (50) values in the range of 27 - 60 microM, as determined by whole-cell patch-clamp electrophysiological experiments.
Asunto(s)
Apocynaceae , Antagonistas Nicotínicos/farmacología , Fitoterapia , Extractos Vegetales/farmacología , Receptores Nicotínicos/efectos de los fármacos , Cardenólidos/administración & dosificación , Cardenólidos/farmacología , Cardenólidos/uso terapéutico , Flores , Humanos , Concentración 50 Inhibidora , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/uso terapéutico , Técnicas de Placa-Clamp , Extractos Vegetales/administración & dosificación , Extractos Vegetales/uso terapéutico , Hojas de la Planta , Receptores Nicotínicos/metabolismoRESUMEN
Targacept Inc, under license from the University of South Florida, is developing a low-dose, liquid gel capsule formulation of the nicotinic acetylcholine antagonist mecamylamine, as a potential treatment for various neuropsychiatric disorders.
Asunto(s)
Mecamilamina/uso terapéutico , Antagonistas Nicotínicos/uso terapéutico , Adolescente , Adulto , Animales , Trastorno por Déficit de Atención con Hiperactividad/tratamiento farmacológico , Niño , Relación Dosis-Respuesta a Droga , Esquema de Medicación , Evaluación Preclínica de Medicamentos , Humanos , Mecamilamina/administración & dosificación , Mecamilamina/efectos adversos , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/efectos adversos , Ensayos Clínicos Controlados Aleatorios como Asunto , Cese del Hábito de Fumar , Trastornos Relacionados con Sustancias/tratamiento farmacológico , Síndrome de Tourette/tratamiento farmacológicoRESUMEN
The symptoms and lethality of intoxication with the acetylcholinesterase inactivator soman are attributed primarily to excessive activation of muscarinic acetylcholine receptors; nicotinic activation is considered of less importance, a notion that may rely on studies that have used nicotinic antagonists at low doses. In this study pretreatment with the centrally acting nicotinic antagonist mecamylamine, 20mg/kg, but not 2mg/kg, prolonged survival in mice exposed to soman, 250 microg/kg (1.5 LD(50)), from 14+/-3 to 135+/-38 min (mean+/-S.E.M.; surviving animals were killed 240 min after soman administration). Pretreatment with the muscarinic blocker scopolamine, 2 or 20mg/kg (but not 0.5mg/kg) prolonged survival significantly (mean for both groups: 91 min), but the animals responded to soman with immobility, irregular respiration, fasciculation, and short episodes of convulsive crawling. These symptoms were absent in animals pretreated with scopolamine plus mecamylamine, both drugs 20mg/kg, a suggestion that they were caused by activation of nicotinic receptors. All animals pretreated with scopolamine and mecamylamine (both drugs 20 mg/kg) survived the full 240 min observation period. Administration of mecamylamine, 5 mg/kg, 5 min after soman exposure to scopolamine-pretreated animals reduced fasciculation and respiratory irregularity and prolonged survival compared to scopolamine alone, but mecamylamine, 20 mg/kg, given 10 min after soman exposure shortened survival (18+/-1 min). These results suggest that nicotinic activation plays an important part in soman-induced symptomatology and lethality but also that nicotinic antagonists given in large doses after soman exposure may have untoward effects.
Asunto(s)
Sustancias para la Guerra Química/toxicidad , Nicotina/farmacología , Intoxicación , Soman/toxicidad , Acetilcolinesterasa/metabolismo , Análisis de Varianza , Animales , Conducta Animal/efectos de los fármacos , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Femenino , Hipercinesia/inducido químicamente , Hipercinesia/prevención & control , Dosificación Letal Mediana , Mecamilamina/administración & dosificación , Ratones , Antagonistas Muscarínicos/administración & dosificación , Rigidez Muscular/inducido químicamente , Rigidez Muscular/prevención & control , Antagonistas Nicotínicos/administración & dosificación , Intoxicación/etiología , Intoxicación/fisiopatología , Intoxicación/prevención & control , Escopolamina/administración & dosificación , Factores de Tiempo , Temblor/inducido químicamente , Temblor/prevención & controlRESUMEN
A placebo controlled, double-blind trial of mecamylamine treatment of cocaine dependence was performed in methadone or LAAM maintained subjects who met DSM-IV criteria for cocaine dependence. After an eight-week placebo run-in screening period, 35 subjects were randomly assigned to receive either mecamylamine (6 mg/day) or placebo transdermal patches for a 16-week treatment period. Outcome measures included quantitative urine benzoylecognine (BE) levels, self-report of cocaine use, cocaine craving, global impression scores, mood, retention, and safety. Mecamylamine was well tolerated, and study retention did not differ by treatment group. Evidence for cocaine use, based on urine BE levels and cocaine abstinence rates, did not differ by treatment group. Self reported cocaine use, cocaine craving, and global impression scores showed moderate improvement in both groups, with a significantly greater reduction in cocaine craving (p < 0.05) and self-rated severity of cocaine dependence (p < 0.05) in the placebo group. This pilot study does not support the effectiveness of mecamylamine for the treatment of cocaine dependence in methadone or LAAM maintained patients.
Asunto(s)
Trastornos Relacionados con Cocaína/rehabilitación , Mecamilamina/administración & dosificación , Antagonistas Nicotínicos/administración & dosificación , Población Urbana , Administración Cutánea , Cocaína/análogos & derivados , Cocaína/orina , Trastornos Relacionados con Cocaína/orina , Método Doble Ciego , Evaluación Preclínica de Medicamentos , Femenino , Humanos , Masculino , Mecamilamina/efectos adversos , Metadona/administración & dosificación , Acetato de Metadil/administración & dosificación , Narcóticos/administración & dosificación , Ciudad de Nueva York , Antagonistas Nicotínicos/efectos adversos , Resultado del TratamientoRESUMEN
Several brominated indole alkaloids and a diterpene (1-7) were isolated from the dichloromethane extract of the North Sea Bryozoan Flustra foliacea. Alkaloid 4 is a new natural product, whose structure was elucidated by interpretation of spectroscopic data (NMR, mass, UV, and IR). All compounds were tested for their in vitro affinity towards the alpha4beta2* and alpha7* subtype of the neuronal nicotinic acetylcholine receptor (nAChR) using radioligand binding assays. Deformylflustrabromine (3) and deformylflustrabromine B (4) were shown to have affinities in the lower micromolar range for nAChRs, differing in their subtype preference.
Asunto(s)
Briozoos , Fármacos Neuroprotectores/farmacología , Antagonistas Nicotínicos/farmacología , Fitoterapia , Extractos Vegetales/farmacología , Receptores Nicotínicos/efectos de los fármacos , Alcaloides/administración & dosificación , Alcaloides/farmacología , Alcaloides/uso terapéutico , Animales , Unión Competitiva/efectos de los fármacos , Fármacos Neuroprotectores/administración & dosificación , Fármacos Neuroprotectores/uso terapéutico , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/uso terapéutico , Extractos Vegetales/administración & dosificación , Extractos Vegetales/uso terapéutico , Prenilación de Proteína , Ratas , Ratas Sprague-DawleyRESUMEN
Neuronal nicotinic receptor (NNR) agonists such as ABT 594 have been shown to be effective in a wide range of preclinical models of acute and neuropathic pain. The present study, using the NNR agonist A-85380, sought to determine if NNR agonists are acting via similar or differing mechanisms to induce anti-nociception and anti-allodynia. A systemic administration of the quaternary NNR antagonist chlorisondamine (0.4 micromol/kg, intraperitoneal (i.p.)) did not alter A-85380-induced (0.75 micromol/kg, i.p.) anti-nociception in the rat paw withdrawal model of acute thermal pain. In contrast, previous studies have demonstrated that blockade of central NNRs by prior administration of chlorisondamine (10 microg i.c.v.) prevents A-85380 induced anti-nociception indicating a predominantly central site of action of NNR agonists in relieving acute pain. In the rat spinal nerve ligation model of neuropathic pain, A-85380 induced a dose-dependent anti-allodynia (0.5-1.0 micromol/kg) that was blocked by pretreatment with mecamylamine (1 micromol/kg). Interestingly, unlike acute pain, both systemic and central administration of chlorisondamine blocked A-85380-induced anti-allodynia, an effect that was determined not to be due to a non-specific effect of chlorisondamine or to chlorisondamine crossing the blood-brain barrier. The peripheral site of action was shown not to be the primary receptive field, since A-85380 had equally potent anti-allodynic effects when it was injected into either the affected or unaffected paw. In contrast, infusion of A-85380 directly onto the L5 dorsal root ganglion on the affected side resulted in a dose-dependent and marked anti-allodynia (10-20 microg) at doses that had no effect when injected systemically. This effect was blocked by pretreatment with chlorisondamine. Together these data further support the idea that different mechanisms underlie different pain states and suggest that the effects of NNR agonists in neuropathic pain may be due in part to peripheral actions of the compounds.
Asunto(s)
Benzopiranos/uso terapéutico , Ganglios Espinales/efectos de los fármacos , Ligadura/métodos , Mononeuropatías/fisiopatología , Antagonistas Nicotínicos/uso terapéutico , Dolor/tratamiento farmacológico , Animales , Antihipertensivos/farmacología , Benzopiranos/administración & dosificación , Clorisondamina/farmacología , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Vías de Administración de Medicamentos , Evaluación Preclínica de Medicamentos , Interacciones Farmacológicas , Hexametonio/farmacología , Masculino , Antagonistas Nicotínicos/administración & dosificación , Umbral del Dolor , Estimulación Física , Ratas , Ratas Sprague-Dawley , Factores de TiempoRESUMEN
The effects of Uncaria tomentosa total alkaloid and its oxindole alkaloid components, uncarine E, uncarine C, mitraphylline, rhynchophylline and isorhynchophylline, on the impairment of retention performance caused by amnesic drugs were investigated using a step-down-type passive avoidance test in mice. In this test, the retention performance of animals treated with the amnesic and test drugs before training was assessed 24 h after training. Uncaria tomentosa total alkaloid (10-20 mg kg(-1), i.p.) and the alkaloid components (10-40 mg kg(-1), i.p.), as well as the muscarinic receptor agonist oxotremorine (0.01 mg kg(-1), i.p.), significantly attenuated the deficit in retention performance induced by the muscarinic receptor antagonist scopolamine (3 mg kg(-1), i.p.). The effective doses of uncarine C and mitraphylline were larger than those of other alkaloid components. Uncarine E (20 mg kg(-1), i.p.) also blocked the impairment of passive avoidance performance caused by the nicotinic receptor antagonist mecamylamine (15 mg kg(-1), i.p.) and the N-methyl-D-aspartate (NMDA) receptor antagonist (+/-)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP; 7.5 mg kg(-1), i.p.), but it failed to affect the deficit caused by the benzodiazepine receptor agonist diazepam (2 mg kg(-1), i.p.). Rhynchophylline significantly reduced the mecamylamine-induced deficit in passive avoidance behaviour, but it failed to attenuate the effects of CPP and diazepam. These results suggest that Uncaria tomentosa total alkaloids exert a beneficial effect on memory impairment induced by the dysfunction of cholinergic systems in the brain and that the effect of the total alkaloids is partly attributed to the oxindole alkaloids tested. Moreover, these findings raised the possibility that the glutamatergic systems are implicated in the anti-amnesic effect of uncarine E.
Asunto(s)
Alcaloides/farmacología , Amnesia/fisiopatología , Reacción de Prevención/efectos de los fármacos , Uña de Gato/química , Plantas Medicinales , Alcaloides/química , Amnesia/inducido químicamente , Animales , Diazepam/farmacología , Relación Dosis-Respuesta a Droga , Medicamentos Herbarios Chinos/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Moduladores del GABA/farmacología , Alcaloides Indólicos , Inyecciones Intraperitoneales , Inyecciones Intraventriculares , Masculino , Mecamilamina/administración & dosificación , Ratones , Actividad Motora/efectos de los fármacos , Agonistas Muscarínicos/farmacología , Antagonistas Muscarínicos/administración & dosificación , Antagonistas Nicotínicos/administración & dosificación , Oxindoles , Oxotremorina/farmacología , Piperazinas/farmacología , Pirenzepina/administración & dosificación , Escopolamina/administración & dosificaciónRESUMEN
Intrahypothalamic injections of d-Tubocurarine (DT) and bicuculline (BM) in the cat produced a fear reaction characterized by terrific mewing, increased locomotor activity, jumps and attempt to escape from the chamber, pupillary dilatation, increased respiratory rate, and sometimes urination and defecation. HPLC analysis showed a significant increase in the noradrenergic system activity in the emotional brain areas (hypothalamus, midbrain, amygdala) and frontal cortex at the time of the fear drive. No changes in the cat's behavior and in the monoaminergic systems activity occurred after muscimol+d-Tubocurarine injections into the hypothalamus. Similar behavioral and neurochemical effects evoked by DT and BM suggest that the fear response evoked by DT does not result from the blockade of N-cholinergic transmission but rather from their action on GABAA receptor complex. The results obtained indicate that the central triggering mechanism for fear drive depends on the blockade of GABAA-ergic transmission.
Asunto(s)
Conducta Animal/efectos de los fármacos , Miedo/efectos de los fármacos , Antagonistas de Receptores de GABA-A , Hipotálamo/efectos de los fármacos , Hipotálamo/metabolismo , Transmisión Sináptica/efectos de los fármacos , Amígdala del Cerebelo/efectos de los fármacos , Amígdala del Cerebelo/metabolismo , Animales , Aminas Biogénicas/metabolismo , Gatos , Femenino , Antagonistas del GABA/farmacología , Inyecciones , Masculino , Mesencéfalo/efectos de los fármacos , Mesencéfalo/metabolismo , Actividad Motora/efectos de los fármacos , Antagonistas Nicotínicos/administración & dosificación , Antagonistas Nicotínicos/farmacología , Corteza Prefrontal/efectos de los fármacos , Corteza Prefrontal/metabolismo , Tubocurarina/administración & dosificación , Tubocurarina/farmacología , Vocalización Animal/efectos de los fármacosRESUMEN
Chemitrodes which permit electrical and chemical stimulation of the same hypothalamic loci were implanted in anterior hypothalamic and preoptic regions. These sites were stimulated electrically using biphasic square wave pulse (1 ms, 60 Hz) at a current strength ranging from 150-800 microA to evoke an aggressive response. At lower current strength of 150-200 micro A, defence response, a sort of non-specific response can be elicited from these regions. Increasing the current strength to 400 microA led to the recruitment of affective and somatic components and changed the response pattern either to affective attack or flight. The loci producing affective attack response were localized more laterally and ventrally while the loci producing flight response were located in the dorsomedial regions of the hypothalamus. In this response the animal made a goal-directed attempt to escape through an escape route. Increasing the current strength to 500 microA in the dorsomedial regions changed the flight response to violent flight, which involved vigorous running with unsheathed claws and attacking objects if obstructed. Similar increase in current strength at loci producing affective attack only led to a decrease in the latency of response and made the attack more vigorous. Microinfusion of carbachol in graded doses of 2-15 microgram at all these loci produced a profound affective display. At lower doses of 2 and 5 microgram, only some components of affective display like alertness, pupillary dilation and ear flatness were exhibited. Increasing the dose to 10 micrograms and 15 micrograms led to the recruitment of other affective components like piloerection, salivation, hissing and baring of teeth. Microinfusion of carbachol at all loci producing affective attack on electrical stimulation produced a prononced affective display while microinfusion of carbachol at loci producing flight response led to the development of defence posture. At six loci a typical flight response was obtained while violent flight was never exhibited at any of these sites. Microinfusion of atropine (10 microgram in 1.0 microliter saline) at these loci completely blocked the carbachol induced response. Both somatomotor and affective components were completely inhibited. However, the responses obtained on electrical stimulation were not totally blocked following atropine infusion and some of the somatomotor and affective components could be elicited with higher current strength. These studies indicate the involvement of cholinoceptive mechanisms in the elicitation of hypothalamically induced aggresive behaviour. Microinfustion of hexamethonium bromide, a nicotinic blocker in 50 micrograms doses did not affect the aggressive response.