Clinical features and pharmacological treatment of migraine patients referred to headache specialists in Canada.

We set out to examine selected clinical characteristics of migraine patients referred to neurologists specializing in headache in Canada, and to document their pharmacological therapy both before and after consultation with the neurologist. Demographic, clinical and pharmacotherapy data were collected at the time of consultation for 606 patients referred to five headache clinics and who were given a migraine diagnosis by the neurologist. Data were analysed as part of the Canadian Headache Outpatient Registry and Database (CHORD) Project. The mean age of the migraine patients was 39.7 years; and 82.5% were female. The majority of patients suffered severe impact from their headaches. Prior to consultation, 48.7% were taking a triptan; after consultation, 97.2% were on a triptan. Before consultation, 30.9% were on a prophylactic drug; after consultation, 70.4% were. 20.8% of patients were medication overusers. Of these medication overusers, 42.4% were overusing an opiate, usually in combination with other analgesics; 21.6% were overusing a triptan. Medication changes made by the neurologists at consultation included a large increase in the use of both triptans and prophylactic medications. Medication overuse, particularly opiate overuse, remains a significant problem in patients with migraine in Canada.

A comparison of disability and psychological factors in migraine and transformed migraine.

The classification of patients with migraine who develop chronic daily headache is controversial, with some classifying such patients as 'transformed migraine'. We compared patients with intermittent migraine attacks and patients with transformed migraine in terms of mean headache intensity on days with headache, depression, pain-related anxiety and headache-related disability. Patients classified clinically as also having tension-type headache were excluded. Aside from the number of days with headache per month, patients with intermittent migraine attacks and patients with transformed migraine were very similar in terms of all parameters studied. Our results support the concept that these two headache groups are closely related.

The involvement of dopamine in nociception: the role of D(1) and D(2) receptors in the dorsolateral striatum.

Determination of the neuroanatomical and neurochemical factors that contribute to nociception is an essential element in the study and treatment of pain. Several lines of evidence have implicated nuclei and neurotransmitters within the basal ganglia in nociception. For example, previous studies have shown that dopamine receptors in the striatum are involved in acute nociception, however, it remains to be determined if dopamine receptors in the dorsolateral striatum are involved in persistent nociception. The purpose of the present study was therefore to determine whether activation or antagonism of dopamine receptors in the dorsolateral striatum influences the nociceptive responses of rats in the formalin test, a model of persistent pain. It was found that micro-injection of the non-selective dopamine antagonist haloperidol into the dorsolateral striatum increases formalin-induced nociception whereas injection of the non-selective dopamine agonist apomorphine reduces formalin-induced nociception. Injection of the D(1) antagonist SCH23390 or the D(1) agonist SKF38393 does not affect formalin-induced nociception. In contrast, injection of the D(2) antagonist eticlopride enhances formalin-induced nociception, whereas injection of the D(2) agonist quinpirole reduces formalin-induced nociception. These results provide additional evidence that dopamine receptors in the striatum are involved in nociception. Furthermore, this study strongly suggests that D(2), but not D(1), dopamine receptors in the dorsolateral striatum are involved in modulation of persistent nociception.

A role of periaqueductal grey NMDA receptors in mediating formalin-induced pain in the rat.

In the present study we examined the role of periaqueductal grey (PAG) N-methyl-D-aspartate (NMDA) receptors in the perception of tonic and phasic pain. Under sodium pentobarbital anesthesia rats were implanted unilaterally with a guide cannula aimed at the PAG. Following a 7-14 day recovery period rats received an infusion of the NMDA antagonist, 2-amino-5-phosponopentanoic acid (AP5), or saline into the PAG. Five minutes after the infusion of AP5 rats were tested for analgesia in the formalin test, or in the hotplate test. AP5 injections into the PAG reduced pain in the formalin test, but not the hotplate test. These data show that NMDA receptors within the PAG are involved in the perception of tonic, inescapable pain as measured in the formalin test, but not phasic, escapable pain as measured in the hotplate test.

Reduction of autotomy following peripheral neurectomy by a single injection of bupivacaine into the cingulum bundle of rats.

Peripheral neurectomy in rats is followed by autotomy of the denervated zone, which is assumed to represent an index of pain or dysesthesia. In the present study, we examined whether a single injection of a local anesthetic (bupivacaine) into the cingulum bundle at the time of nerve section could reduce autotomy. It was found that a temporary anesthetic blockade of the cingulum at the time of nerve section delayed the onset and reduced the overall degree of autotomy. However, injections given shortly after nerve section had no significant effects. These results demonstrate that temporary blockade of cingulum activity at the time of nerve section reduces autotomy for periods that exceed the duration of the anesthetic block.

The effects of olfactory and somatosensory desensitization on Fos-like immunoreactivity in the brains of pup-exposed postpartum rats.

Fos-like immunoreactivity (fos-lir) was examined in sites within the "maternal circuit" in postpartum female rats that received various sensory desensitizations and were exposed to pups for 1 or 2 hr. Neither olfactory bulbectomy nor thelectomy (nipple removal) significantly reduced the fos-lir in the anterior medial preoptic area (MPOA), although reductions following bulbectomy in medial amygdala did occur. Peripherally induced hyposmia by ZnSo4 reduced fos-lir in the olfactory structures (olfactory bulbs, piriform cortex, and olfactory tubercle), in medial and cortical nuclei of the amygdala, but not in anterior MPOA. Application of the topical anesthetic Emla to the ventrum only reduced fos-lir in the somatosensory cortex. Combined olfactory and ventral desensitizations produced marginal reductions in posterior MPOA. It is suggested that the MPOA is primarily involved as part of the effector system in the expression of the behavior. In contrast, the amygdala is involved in processing sensory cues received from pups during dam-litter interactions.