A reliable, rapid and inexpensive method for producing and implanting chronic cannulae into brains of small animals

Acute and chronic behavioural sequelae resulting from intrastriatal injection of an NMDA agonist

Unilateral and bilateral injections of cis-2,4-methanoglutamate, a potent and selective NMDA agonist, were made into the striatum of rats. Unilateral injections elicited MK-801-sensitive dose-related increases in contralateral turning, beginning 10-15 min after injection. Bilateral injections elicited typical seizure-like behaviours commencing approximately 80 min postinjection. Forty-eight hours after unilateral injection, and presumably after lesion development, no spontaneous preference for turning was seen. Upon challenge with apomorphine (1 mg/kg SC), ipsilateral turning lasting approximately 60 min was seen. Correlates are drawn between this model and some of the features of Huntington's disease.

An easily constructed, reusable, bipolar, concentric stimulation electrode for use with intracranial guide cannula assemblies

The construction of a stimulation electrode is described. This electrode is removable and is designed to be used with intracranial guide cannula assemblies. It is a concentric, bipolar electrode, and is easy and inexpensive to assemble from materials readily available in most laboratories. A detailed description is also given of procedures to connect the electrode to stimulation equipment in a manner that would minimize interference by the test animal with the operation of the electrode.

Modulation of the rat mesolimbic dopamine pathway by neurokinins

The locomotor activity (LMA) response induced after infusion of selective neurokinin (NK) agonists into the cell body (A10) and a terminal region of the mesolimbic pathway of the rat was investigated. Infusion of the NK1 receptor-selective agonist, GR73632, into the ventral tegmental area (VTA: A10) or the nucleus accumbens (NAS) significantly and dose-dependently increased basal LMA. Agonists selective for the NK2 and NK3 receptors, GR64349 and senktide respectively, had no effect on LMA after intra-NAS infusion. The LMA induced by GR73632 is mediated via dopamine (DA) since the response was abolished by haloperidol. From these studies it would appear that the elevated LMA reported previously after VTA or NAS administration of substance P probably occurs via NK1 receptors. Such data supports the notion that endogenous NKs are likely to be important in modulating the mesolimbic DA pathway and, as a consequence, compounds which antagonise their effects could be useful for the treatment of disorders associated with this system. However, simultaneous infusion of the NK1 agonists, +/- CP-96,345 and its analogue CPQ, into the VTA did not attenuate the LMA induced after intra-VTA infusion of GR73632. Co-infusion of the NK1 antagonist CPQ, but not +/- CP-96,345, attenuated the LMA response induced by GR73632 in the NAS. The apparent poor susceptibility of these responses to blockade by the recently developed non-peptide NK1 antagonists was unexpected but may reflect their poor affinity for the rat variant of the NK1 receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioural consequences following infusion of selective neurokinin agonists into the median raphe nucleus of the rat

The locomotor activity induced after infusion of selective neurokinin (NK) agonists into the median raphé nucleus of rats was investigated. In photocell cages, the NK-2-agonist, GR64349, and the NK-3 agonist, senktide, both increased motor activity in a dose-dependent manner. However, the NK-1 agonist, GR73632, had little effect over a range of doses. In the open field, the motor effect of all three NK agonists was identical to that observed in the photocell cages. In addition, senktide induced straub-tail, hind-limb splaying and various oral movements. Such effects were not noted with the other two agonists. These results suggest that activation of NK-2 or NK-3 receptors by the neurokinins, in the median raphe nucleus of the rat, leads to an increase in locomotor activity.

Behavioural and biochemical responses following activation of midbrain dopamine pathways by receptor selective neurokinin agonists

Preferential activation of mesolimbic and nigro-striatal dopamine (DA) pathways by receptor-selective and peptidase-resistant neurokinin (NK) agonists is reported. The DA cell body region of the mesolimbic pathway appears to be activated by NK agonists selective for NK-1 and NK-3 receptors whereas the DA cell bodies in the substantia nigra are under an excitatory NK-2 receptor-mediated influence. Stimulation of the mesolimbic DA pathway by NK-1 (Ava[L-Pro9,N-Me-Leu10]SP (7-11) [GR73632]) or NK-3 (Senktide) agonists increase locomotor activity. Additional studies showed that this elevated motor response observed after intra-VTA infusion of GR73632 was accompanied by a corresponding increase in DA turnover in the terminal fields of this pathway. Similarly, unilateral activation of the nigro-striatal DA pathway by NK-2 selective agonists (Ava (D-Pro9) SP (7-11) [GR51667] or [Lys3,Gly8,R-Lac-Leu9]NKA (3-10) [GR64349]) elicit contralateral rotational activity and an increase in DA turnover in the ipsilateral striatum. The rotational response was attenuated by prior administration of an NK-2 antagonist (cyclo (Gln, Trp, Phe, Gly, Leu, Met)] L-659877]) into the nigra. Peripheral injection of haloperidol, a DA antagonist, also blocked the NK-2 agonist induced rotations.

Procedure for assessing the behavioral effects of novel anti-parkinsonian drugs in normal and MPTP-treated marmosets following central microinfusions

Comparison between drug effects in MPTP- and non-MPTP-treated marmosets following intracerebroventricular (ICV) and intraputamen administration are given in the present report. Both side-effect profiles and the ability to reverse MPTP-induced hypokinesia were assessed using a variety of dopamine receptor agonists (quinpirole, PHNO, ADTN), cholinergic antagonists (scopolamine, secoverine, himbacine), a glutamate receptor antagonist (MK801) and a 5-HT receptor agonist (8-OH-DPAT). Our results show that direct infusion of agents into the putamen or via the ICV route can reverse parkinsonian-like symptoms in marmosets. Furthermore, chronic implantation of cannulae into the putamen or ventricles of nonhuman primates can be useful in assessing the therapeutic activity of agents that do not readily cross the blood-brain barrier.

Oxytocin effects on lordosis frequency and lordosis duration following infusion into the medial pre-optic area and ventromedial hypothalamus of female rats

When infused into the medial preoptic area of ovariectomized female rats treated with estradiol benzoate (3 micrograms) and progesterone (150 micrograms), oxytocin was found to increase the lordosis frequency and the lordosis duration. Oxytocin administered into the ventromedial hypothalamus increased the lordosis duration but not the lordosis frequency. In the mesencephalic central grey, oxytocin did not significantly affect lordosis. Oxytocin in the ventromedial hypothalamus facilitated lordosis duration at doses which were ineffective in the medial preoptic area. This contrasts with the pattern of results observed for lordosis frequency. These results lend support to the hypothesis that the lordosis-facilitating actions of oxytocin in the ventromedial hypothalamus are due to a permissive effect of progesterone and that the ventromedial hypothalamus and medial pre-optic area may control different aspects of lordosis.

A convenient and inexpensive method for chronically implanting multiple intracranial cannulae

A simple and inexpensive method is described for the chronic implantation of multiple cannulae in small animals. This method employs a simple die cast from dental acrylic cement which is then repeatedly used to retain the cannulae during implantation. No special workshop tools are required and assembly is rapid.

Neuronal sites mediating locomotor hyperactivity following central neurokinin agonist administration

The stable substance P analog, DiMeC7, increases spontaneous locomotor activity after infusion into the lateral ventricles or median raphe nucleus (MRN). The elevated locomotion observed after intracerebroventricular (ICV) infusion of DiMeC7 was attenuated, but not blocked, by bilateral 6-hydroxydopamine (6OHDA) lesions of the ventral tegmental area (VTA). In contrast, bilateral 6OHDA lesions of the nucleus accumbens (NAS) blocked the motor activity induced by ICV administration of DiMeC7. Similar lesions did not affect the increases in motor behavior observed after MRN infusions of DiMeC7. However, the hyperactivity following MRN microinjections of DiMeC7 was attenuated by intraperitoneal administration of the dopamine (DA) antagonist, haloperidol. The results suggest that ICV infusions of DiMeC7 increase locomotor activity by acting directly on neurons in the NAS and in part by influencing, directly or indirectly, the activity of DA cells in the VTA. The increased motor activity seen after MRN administration of DiMeC7 appears to depend on DA neurons but not on projections to the NAS.

Neuroleptic-induced catalepsy as a model of Parkinson's disease. I. Effect of dopaminergic agents

Catalepsy was observed in the rat following intrastriatal injections of the dopamine antagonists sulpiride or fluphenazine and after subcutaneous administration of fluphenazine. The neuroleptic-induced catalepsy was reversed by the classical anti-parkinsonian agent L-DOPA and by agents that function through dopamine systems such as d- and methamphetamine and the direct D2 receptor agonist quinpirole. The D1 agonist SKF 38393, and the D1/D2 agonist apomorphine, were ineffective in this model. These results support limited use of the rat catalepsy model for the screening of potential anti-parkinsonian compounds and indicate that this procedure can provide valuable information concerning striatal dopamine function.

Place aversion induced by the substance P analogue, dimethyl-C7, is not state dependent: implication of substance P in aversion

Intraventricular infusion of the stable substance P analogue, DiMethyl-C7, was found to produce aversion in a place conditioning paradigm. This effect was independent of state dependent learning since the place aversion was also seen when the subjects were tested under the influence of the drug. A role for substance P in aversion is discussed.